Thank you!

Thanks for watching, I find this system very interesting, too. One of the unique features of this design is the way the thermostat controls flow from the radiator on the cold (return) side. The wax pellet and spring are immersed in the hot liquid but the valve it moves is on the cold return hose. The hot side (the hose sending hot coolant to the radiator) is always open, but coolant won't flow through the rad until the cold side valve permits flow. This means that even before the thermostat heats up enough to open, the radiator is subject to systemic pressure. A conventionally designed system isolates the radiator from the high pressure side until the thermostat opens on the hot side. 20 years ago we had an older Suburban that blew the radiator tubing out, caused by a failed thermostat that didn't open before the coolant boiled itself into a high pressure state. I found it a strange way to fail until I understood the unconventional, dual valve design. The other problem with this design is the fact that if the bottom valve doesn't seal well, your engine could run chronically hot because more coolant is bypassing the radiator through that huge bypass hole. Older style bypass tubing was a small diameter passageway that limited flow simply because the bypass tubing couldn't take a big volume. It's a good idea to replace the thermostat if you have an overheat because the wax pellet could melt enough to dissipate and cause a chronically underperforming system that is not easy to diagnose.

Thanks, man.

That's a good point, some cooling does happen at the core. Veterans say if the engine is running a little warm and you are trying to limp home, you can put the cab heater on full blast in the summer and you'll get better engine cooling (AC off). However with the damage possibly caused by continuing to drive with an overheating engine, I would hesitate to do that. In your case, if the thermostat valve that opens and closes that short circuit pathway fails, you may just run a little hot. So, when you are in there, have a look at the themostat and if in doubt, replace it. Some systems do not have that short circuit valve, it stays open all the time. Thank you for watching!

M. Rivera Thank you!

Thank you. On most vehicles the weep hole is hard to find and you don't get a good view. Once the water pump is disassembled on the bench, it is easy to understand the more subtle findings you often get on the car. What I find intriguing about the Chev design is the way the thermostat closes the large bypass hole at the same time as opening the return pathway from the radiator. More traditional designs only do the latter, and the bypass is always open but much smaller (so there is more resistance to coolant flow in the old design). With a huge bypass hole, it is less work to spin the water pump while the vehicle is warming up, so I believe the Chev design is there to improve warmup fuel efficiency.

+speed955i Yeah, me too. I've learned from experience it's usually better to wait til it fails, since I get into trouble if it ain't broke yet, ha ha.

Thanks for stopping by. Dave

Hey man, thank you. It's nice to get a visit from a real pro.

Lol thanks..love ur channel..keep up the good work :)

Thanks, man.

Rebuilding a 302 skip white Hc 8050 s water pump

Shawn Dinterman I'm glad it helped, thanks for the followup.

Thank you, it was a fun one to put together.

You're welcome, I'm glad it helped. The economy of North America is upside down! Throwing something like this away rather than fixing it seems fundamentally wrong.

You're welcome, I'm glad it helped.

Thanks.

Yeah, thanks for watching, Steve. Dave

Welcome. Got it finished with your help. Seems easy now.

Thanks, I still have this old Suburban, now with more than 400,000 km. With adequate maintenance, those things never die.

Is there a video explaining failing thermostate?

@@tipsreviews7476 Not specifically, but I did touch on it in a cooling system video titled "understanding marine diesel engines". The thermostat in the Yanmar is similar to the Chev thermostat because it also makes contact on the back, effectively giving two sealing surfaces, one of which is open when cold, the other open when hot. I also did a cooling system playlist on the channel.

@@spelunkerd thanks for the response. My engine fan is always running but my truck isn't overheating. Wonder if it's the thermostate?

@@tipsreviews7476 The electric fan in most cars is set to come on if AC is called for in the cab, even if the engine just started. So, remember to turn off AC if you want to watch fan activity. The fan is controlled after the PCM reads the temp sensor, so if fan is coming on when cold, I'd be looking at the temp sensor first. If the fan is run off the belt, the viscous clutch inside the fan controls speed, but those old style fans did always run even when cold. You can tell if the thermostat is open by putting a hand on the top radiator hose to see if it is warm. The thermostat doesn't command the fan on so unless you have overheating or a failure to warm up quickly I'd be looking elsewhere. A scan tool with live data will make this effort a lot easier and faster.

@@spelunkerd thank you I subscribe to your channel . Great content. 👌

+Tbirdfancar Thank you.

Thanks!

Thanks, brother.

Great question, I suspect flow from a heater hose in a car with this design may be inadequate until the thermostat warms up. I believe you're talking about a block heater, used for locations where cold starts are a problem. Once before I installed a block heater. In that case I simply followed the (Toyota) manufacturers directions with an OEM part, for about $40. Cheap. Whole teams of engineers design those parts, I don't see a reason to drift away from the standard design. I have a block heater in my Suburban, I've never traced the wire back to see where it is mounted. You can buy cheap glue-on 120 volt heaters that are designed to stick to the bottom of the pan, heating through the steel of the pan, but they don't work nearly as well as those that deliver heat to the block internally through the cooling system. I would avoid heating coolant very close to the thermostat, since if the thermostat is fooled into thinking the engine is hot you may paradoxically cause a delayed warmup because the big mass of cold water in the radiator would be allowed to enter the cycle sooner than it should. A properly functioning cold thermostat slows water flow through the radiator, isolating a big mass of coolant inside the rad until the engine has a chance to quickly reach operating temp. In this Chev design a cold thermostat offers a low resistance bypass, short circuiting coolant flow, so recently warmed fluid immediately returns to the engine without having to take the higher resistance pathways through heater core or radiator.

@@spelunkerd ok thanks for the explanation. Your insights are much appreciated!

I put it into a 10 ton press, it is the size of a big desk, not exactly a garage tool. No, I never found a set screw, it's just pressed into a blind space with the weep hole on the other end. The bearing rusts onto the outer race and it comes off by breaking the bearing, much like a wheel bearing comes off, in pieces.

The biggest challenge is to dissect this "creature" using home tools ..but I did iiiiitttttt ..!! ..LOL...LOL kzfaq.info/get/bejne/n7yBo7d6qbLUqZc.html

There are many factors in involved in where the sweet spot is for engine temp. I did another few videos of the cooling system in the little 3 cylinder Yanmar diesel engine, and it has a similar two valve bypass system as well. It also runs cooler. Thank you for stopping by!

That was an OEM pump made by General Motors, but other details are lost. Although very old now, there is still a healthy aftermarket for these pumps.

Excellent question. Yup, all centrifugal pumps pull fluid from the center and fling it outward, for more info search 'centrifugal pump'. Here's a video that explains it more clearly. kzfaq.info/get/bejne/jM6TYMt2z86VYn0.html Regarding your truck with temp spikes at idle, check to be sure your cooling fan is coming on, or if it is belt driven check to be sure the fan clutch is working and the fan is spinning correctly. Check the coolant level at the radiator cap, if possible (with engine cold so you don't burn yourself). You may be able to see coolant turbulence as the fluid is moving by, verifying that your pump is working. Also feel the hoses leading to and from your radiator to verify they are different temperatures, also verifying your thermostat is opening and your pump is working. Good luck!

I don't know. As far as I know, they are solid.

@@spelunkerd I just chopped 2 off are solid and good to go. Made room for my fan setup just hope it doesn't mess up any balancing of the shaft.

Those are all good points, I guess it's old school phraseology now. As you probably know there are some systems that don't use water at all, though I have some concerns about engine safety with those systems. Search "waterless automotive cooling systems" and you'll find lots of articles. That said, a water based cooling system seems to be the weakest link as far as long term corrosion and vehicle repair goes. I try to save money by using concentrated coolant and adding distilled water later, though the premixed solutions get around the issue of impurities that people might introduce later. Even though new terminology uses the word coolant, the vast majority of molecules in the fluid are simple H2O, and >99% of vehicles on the road today have a water based system. The coolant that is added is there to raise boiling point and to lower freezing point, and of course other additives are there to inhibit corrosion.

Excellent, I've learned even more as a result of your efforts. Thank you, keep up the good work!

Wonder if the heat made the seal more flexible or expand, then stopping the leak until it cooled?

Yes there should be some movement, though much of it will be through the huge bypass hole when this style of dual-valve thermostat is removed. That technique, to remove the thermostat completely, worked well in older style single valve thermostats but the story is more complex with a dual valve unit. Also note that your system needs to be adequately burped, since a water pump doesn't work very well when there is trapped air near the impeller. Trapped air absorbs the energy by compression, so the pump can't move much fluid until the air is replaced with fluid. I show how to burp the system with a no spill funnel in a couple of my videos that are listed in my cooling system playlist. Good luck!

Yeah, I didn't mean to confuse anybody with that. When you look at the fins, you can see which way it has to turn to throw the fluid out from the center. I guess if the serpentine belt were put on wrong it might send water in the opposite direction, but the OEM belt probably wouldn't fit if the routing was wrong. There should be a diagram of the belt routing on a sticker somewhere under the hood, but if not you'll find it in the dealers repair manual. One tip that sometimes helps is to remember that ribbed pulleys contact the inside of the belt, and the smooth pulleys contact the smooth outside of the belt. Some water pumps have plastic impeller blades, which can break and throw little parts down the line, so it might be wise to have a look. I've also occasionally seen radiators that were so badly corroded they don't allow much flow. Of course remember to burp the system to be sure trapped air is completely removed. Thanks for your comment here.

That's a good question, I don't know for sure. If you wanted to you could back flush the engine and heater core, flushing with water from a hose backwards to drive any possible bearings backwards into a pail. I'm gonna give you a big fat guess that the risk is small.

Trapped air, you need to burp the cooling system. Leave the radiator cap off, start the engine, and add coolant to keep it topped up while engine is running. The water pump will push that air pocket into the rad, but it won't be complete until the thermostat opens. You'll notice that because you'll feel the upper rad hose go hot. Then stop, put the cap back on, wait a day, recheck and refill levels. Several videos on my cooling system playlist go over that in detail. Good luck!

@@spelunkerd funny enough, im currently watching your chevy axle video as typing. You do some good stuff. Gonna look into speed sensors tomorrow for the 4x4 issue im having.

@@spelunkerd so I followed your steps last night. It led to me adding that .5 to the radiator. Should still need 1.5gal added. Im re-doing your steps. Do you think that will fix it or am I missing something?

@@TheGraffiti600rr Some vehicles have valves to allow trapped air to escape, check the OEM dealer repair manual for that, I use alldatadiy. Some mechanics use a vacuum suction technique, to evacuate trapped air, I don't. The automatic burping mechanism relies on a good radiator cap, check the seals there to be sure the siphon mechanism from the coolant recovery bottle will work overnight as the engine cools. It may take many days and multiple refills if automatic burping is the plan. Good luck!

Trapped air is the most common source of confusion. Run the engine with cap off, keep filling and watching until engine is completely warm to be sure all trapped air has been burped clear, then put cap back on and let the cap do the remainder of the burping. Be sure you've got the correct cap and thermostat for the vehicle. These complicated chevy thermostats have two valves so it would be expected to overheat with no hot air from the heater core if the thermostat is removed, because hot coolant can bypass back into the engine without going through the radiator or heater core. In the video just after 5:00 you'll see how warm coolant can bypass the radiator and go directly back to the engine if the thermostat doesn't close off that opening. If in doubt I'd get a thermostat from the dealer to be sure it's correct for the job.

Yes, some leaks happen only at rest because pressure holds the seal in place when the vehicle is running. At night that pressure difference is actually reversed, drawing fluid from the coolant reservoir back into the system. That kind of leak is a kind of 'ball valve effect'. I suppose if the mechanism for automatic filling were blocked, such as a stuck shut valve in the radiator cap or a kinked reservoir tube, then negative pressure inside the system overnight might drop more than it normally does. I did a video on the radiator cap, "Hidden genius behind an engine cooling system" that is worth a look. Whenever you have cooling system issues the first place to inspect is that rad cap and reservoir fill tube. You should be able to pry that second tiny one way valve of the rad cap up. Look closely for sticking or cracked seals there. All of that said, you want to go to where the leak is and decide how to deal with it. It's too bad we end up replacing the water pump because the back seal doesn't last as long as the pump does. You might be able to find a new seal, but most guys who take the repair that far end up replacing the whole pump, if only to try and prolong the time to the next repair. Good luck!

Well that explains why the leak is the worst when the cap is off such as when I'm filling the coolant system

Rebuilt water pumps come with the pulley. Given how much effort it was to remove (with the use of specialized tools) you may be better to go that route. Alternatively you could find a pump at a salvage yard and pull the pump pulley off with a three jaw puller. The pulley itself may be hard to find by itself on the retail market. I got most of my automotive tools at Princess Auto here in Canada, in the US a similar store is Harbor Freight. The pulley is just pressed onto the shaft of the pump, I would use a press, but if you don't have one often all you need is a hammer and block of wood. Good luck! I did two other videos of how to replace the water pump in a 2000 GM suburban, you may find those helpful. When you get it apart, don't be surprised if all you need is a new fan clutch, those often go bad.

Thanks for the reply. I was replacing the fan clutch and a misthreaded (apparently) fan clutch stripped the threads on the pulley as I was attaching it. So now it's replace the whole water pump or just the pulley. I actually have access to a new, old stock pulley but was concerned about getting it attached to the water pump while still in place. Seems like the hammer and block approach might damage the water pump and/or spindle while it's being hammered. I'm wondering if there's an attachment tool for this application like the puller/installer for power steering pumps. kzfaq.info/get/bejne/j6-ZiMygsc6zqJc.html

@@nkr3637 You might be able to find something, though it needs to fit inside the space behind the radiator if you do it on the car. I don't remember if there is a threaded concentric hole inside, the way a power steering pump installing tools work. I share your concern about damaging the pump bearings during the install. The other option is to switch to electric, which offers slightly better gas mileage and more strain on the alternator. Electric fan switch kits are widely available.

I've been running Dexcool in this vehicle since I bought it new, and have never had a problem. Still driving it now, presently with 360,000 km. My opinion of Dexcool is if it never overheats you'll never see the issues of clogging that have been described, and I suspect many of those are due to other factors like running dry of coolant or having other owners put stop leak in. I don't think the Dexcool is causing many problems by itself. Switching would not be a big problem, either, if you choose one that is compatible with aluminum. Universal coolant would be reasonable, but I've found no reason to switch.

Thanks for the reply! I guess I will leave it & monitor it better with a voltmeter & PH test strips since I just changed it yesterday. What do you think caused the original orange gaskets to fail (The new OE ones that came with the new OE water pump were black & had a slightly different design)? What do you think that black substance is around the silicone gasket & inside the water pump water jackets? I have seen it on almost all the photos & videos I watched preparing to do the job. Are the intake gaskets made of the same material & due to fail as well?

On mine the black areas were wet from leaking coolant. The solid substance there was mostly residue from the old gasket, probably mixed with grease and maybe even old RTV. Yeah, with the heat and shrink of dramatic thermal changes, over time few gaskets can survive the long term. Cheers!

I had a better look at the old parts. Thankfully, It looks like the gaskets were in fact OK & I did see evidence of leaking from the pumps weep hole. The black seems to be around the outside edge of the orange gaskets on the motor side & is hard carbon like. There is also a black coating on the passages but its just a thin coating. Maybe thats how Dexcool protects the metal? The pump spins fine which is weird because I thought that the bearings were shot since I heard clicking sometimes but I am guessing that the clicking was cavitation from the air in the pump from the failing seal? I put the thermostat in boiling water & realized that only the top moves to allow fluid from the lower radiator hose in. The lower spring & metal disk are the bypass valve & work with water pressure & spring tension. From the Service Manual; "The thermostat also provides a restriction in the cooling system, after it has opened. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block." This has been a great learning experience.

These are a simple centrifugal pump, used in many engineering applications. There are good videos describing how these work in detail, however the basic principle is that the rotor is driven by the fan belt, causing water between blades to be flung outward as the shaft spins. The inlet is central, so cold water enters near the shaft, and the outlet typically has an increase in diameter to reduce the high outlet pressure spike, promoting coolant movement. When water molecules slam against the outlet wall they deflect to follow piping that leads to the engine cooling passageways. The limiting factor for centrifugal pumps is the low pressure spike at the inlet, which in the extreme can cause vaporization of water molecules and inefficiency. So, inlet water needs to be as cold as possible.

I know what you're saying. Thing is, when the bearing seats into the aluminum housing, it oxidizes into place, and when you try to remove it the pressure required is so high the bearing fails before the tight connection lets go. It is similar to a pressed-in wheel bearing. You often can't get the bearing out without destroying it. That said, I believe if you find a replacement bearing, rebuilding it should be easy enough. After all, that is actually what rebuilders do with the core they get back.... Unfortunately finding parts, paying for shipping, hoping they'll fit, and getting the job done quickly may be problematic. Similar to rebuilding a starter motor, finding those small parts may be tricky. Good luck!

Good question. I’ll guess it could be done by replacing the belt driven pump and fan, perhaps even with a tiny fuel economy advantage.

Good question! Older style pumps like this one have free flow to the heater core all the time, but many newer systems have a solenoid-controlled valve, as you say. In the video you can see where the heater hoses attach, and they are very close together, separated by the bypass hole which is controlled by the thermostat. When that hole is cold and open, pressure on the two hoses is similar so there won't be much flow to the heater core until the thermostat warms up to close the bypass hole. So, in this mechanical design, cold water in both the heater core and the radiator will not be moving very much until the thermostat moves to the hot position. After the bypass hole is closed you get differential pressure that will drive flow around the heater. You could clamp the hose on either or both sides if you wanted to bypass the heater core, though it would interfere with cooling since the heater core does contribute a small amount to engine cooling. I scratched my head when I began to understand the mechanical complexity of this pump. Part of the justification for designing it this way was to improve fuel efficiency by reducing the work needed to move water before the engine has warmed up. Of course the bigger reason is to speed warmup by isolating a big volume of cold water in both the rad and the heater core. The engine always turns the impeller, but since water is short circuited through a large and short bypass hole the hydrodynamic resistance during warmup is minimized. This also gives the tech a clue to diagnosis, since in this style pump a "stuck cold" thermostat should give reduced heat inside the cab, on top of running too hot. However with two valves and complexity as to how a thermostat might fail, that is not a particularly useful sign. Newer cab designs added a heater hose solenoid anyway, since the engineers didn't want the heater core to confound AC efforts to cool the cab after warmup.

thank you for your quick reply. You do very well in the water pump system. great of you. i think after the bypass is shut. if you have deleted the heater core, and use a loop hose instead of block off the heater tubes, the hot side will be suck into the cold side via the loop hose.that will reduce the effective cooling i think.If i am wrong you can say it to me.

Yes. Old style systems had an "always open" bypass tube that limits flow because the tubing is fairly small diameter with high resistance. With those systems, when the thermostat opens a pathway to the rad, more fluid goes the lower resistance route through the rad, even though some coolant ends up going through the higher resistance pathway through the bypass even when hot. Those systems have to be designed with a little more reserve because some warm fluid takes a short pathway. As you say, a loop in place of the heater core would allow fluid to short circuit mostly when the thermostat is in the hot position, reducing cooling when hot because some warm fluid that follows the bypassed coolant hoses warms the cold fluid coming back from the rad. New radiators have much smaller tubing which means the resistance in the rad might be higher, increasing flow through bypassed heater hoses. I don't see a big advantage to maintaining continuity between the heater hoses if they aren't used to warm the cab.... Also note that the diameter of the heater hose nipples on this water pump is slightly different when you compare the warm side to the cold side, which might make it a little tricky to use one hose to connect the two nipples. If you can get one hose to seal I suppose you could just clamp that tube....

Not off hand, unless I included it in the video where I removed the pump and installed another one. I subscribe to alldatadiy to get access to the OEM repair manual, it's worth a look.

Excellent question, certainly a favorite. That was an old farmer's trick, it seemed to work great in the summer. Here's my first thought. These engines are designed to run at ~180 deg F, so regardless of season they start out too cold. Of course it's nice to have heat in the cab, but more importantly when cold the thermostat makes the coolant bypass the radiator to speed warmup. So without a thermostat, engine warmup is -also- always slower, regardless of the season, because cold antifreeze should bypass the radiator to go right back into the engine. Note that the cold volume of antifreeze trapped in the radiator is held there until the engine is up to operating temperature, so the initial volume of coolant the engine has to heat is smaller. It is said that the majority of engine wear happens in the first few minutes, because cold oil doesn't flow well through narrow passageways. These engines are designed to run at about 180 def F, and the PCM reacts to colder coolant temperatures by choking down intake and increasing injector pulse width. It may take longer for your engine to go into closed loop because the O2 sensors and cat require high temperatures to work properly. So, I'll guess that even with summer use only, your engine may not last as long and may have poorer startup fuel consumption and poorer emissions without a thermostat. One thing to note is that some thermostats have a tiny hole to allow trapped gas through. Remember to install the thermostat with that hole at the top. In the case of the Chev, that's not an issue because you can't install it upside down. If you find a hole in a thermostat remember to put it at the top. Thanks for watching, these kind of questions enrich the thread and make the effort worthwhile.

+Ruben Quintanar That's the way they typically work, opening to direct water through the rad once a threshold temp is reached. However you'll notice this one is a little different, unusual. In the water pump shown for, the thermostat closes the bypass tract when threshold temp is reached. In all cases, the thermostat is bathed in coolant that is coming out of the engine, and the bimetal coil of the thermostat is always on the engine (hot) side.

+spelunkerd i see, this makes sense now, thanks for your reply :like:

+spelunkerd, it's not a bi-metal coil of thermostat. Proper lingo there is wax servo motor (I hold an expired patent in a related function). The wax used melts at 180 or 195 degrees and as it does so the expansion of the now liquid wax forces the thermostat to open much like a hydraulic cylinder would operate that poppet valve. Ice expands as it freezes, wax is the opposite of that. One thing I have notice over the years from the early style pumps to the latest ones is that the weep hole is now designed for obsolescence rather than the diagnostic function you mention which used to be quite useful in that regard and of those you speak the truth. The old style weep hole was on the bottom where the coolant would leak away not causing the bearings any harm. Today's water pump places the weep hole well above the bearings in order to render them trash asap. $50,000 and I have to drill my own weep hole.

+Lee Barnes Hey, Lee, thanks for contributing to the thread, those are insightful remarks. Dave

you mean wax pellet, not bimetal coil, right?

Regarding the waterless coolant idea, that's a great question, one that is hard to answer as a brief reply. One thing I like about water is that, even under pressure, it boils at a fairly safe temp, giving the driver an unmistakable message (steam from the hood) that he must stop the vehicle immediately. While water is boiling the extra energy is consumed by the change of state and so temp doesn't rise very fast at that point. That thermal plateau allows the driver to usually stop the car before the engine is ruined. Waterless coolant that is on the market now has a much higher boiling point. Not only do you lose the physical warning, you also lose that safety plateau where the rise of temp is temporarily stabilized by a change of state. So, as much as I acknowledge that water is the source of many problems in today's engines, today's waterless coolant does have a couple of drawbacks. The extra cost of waterless coolant is probably part of the issue for new vehicles, as well. The main bearing is sealed, but when I put it in the press I broke it in half to get it apart. Thanks for your comment, Allen!

The bypass channel is large but just beyond that opening the hoses to the heater core are normal size. A big bypass allows a fast warmup before the car hits operating temp, then that valve closes and fluid is routed through the radiator. I did a recent (better) video of a marine diesel cooling system on my channel, and I show more detail as to how that two valve thermostat works. Amazing engineering.

Excellent question. As you know, traditional thermostats can be removed, with the main problem being slow warm up when cold, no overheating. However in this design a missing thermostat will cause the engine to warm up a little more slowly AND run very hot after warmup. It may not be so bad as to cause a steam over, but neither the radiator nor the heater core will get the directed circulation to move heat effectively.

Nice to meet you. We live in Victoria, Canada, ha ha.

Remanufactured pumps don't last very long, the seal separating the bearing from coolant tends to go first. 5 years is sadly about average, shorter with new cars. Over twenty years on this 2000 suburban, the first lasted about 15, the second about 5 years. Most guys replace the thermostat at the same time, keep an eye on the temperature gauge after it is done. This thermostat design can sometimes fail to close completely during hot weather, causing a bypass of the radiator and a hot running engine. Your only clue may be the gauge.

Oh, thanks for your clarification, you're possibly right. In this case I couldn't see a way to take it off the other way. The head of the impeller was frozen to the shaft, covering the end completely on that other side. I suppose I could have tried to pry the impeller off, but with a press I knew it would be easier to force it off, leaving the impeller in position to more easily see how the system works. Thank you for watching.