This is the best S10 vacuum leak video. This dude really goes over all the possible problems.

That place on the check valve tee goes to the vacuum reservoir in the fender, the engine pulls a vacuum on the tank and the check valves keeps the vacuum tank at a constant level

Best video that I've seen yet. I already ordered the switch and actuator but I still need a couple more jack stands and warmer weather before I start wrenching on the 03 S10.

I have a 1999 blazer had my oil changed and my shop told me my 4wd was gone, I was thinking want would make the engine check light come one and 4wd light to, 5 easy things to check for the 4wd fuses, dash 4wd switches, vacuum hoses, transfer case vacuum switch, actuator. Mine turned out to be the vacuum hose. When I fixed that my 4wd and engine check light went off. I'm so proud of myself. Thankyou for all the videos. You helped me become more of a independent women. Please make more videos I'd love to watch and learn more Thankyou again 💓

thanks Adam just bought a 2002 bought new tires Falken Wildpeaks will be heading into the mountains this coming wknd hoping everything works, the video was great

That loogie at 1:30 was fucking hilarious. You can hear that thing smack concrete. Great vid.

most helpful video I'm having the exact same problem with the check valve and broken vacuum hose on my o1 blazer . easy fix for me now also check pcv valve and hose.. thanks again from Puna Hawaii

Mine is a S10 4x4. I changed the Actuator cause it was ripped and had water in it. Nothing I got mad and here is where I am on this video. He man I looked and looked for help online videos but seemed nothing could help my problem with 4x4. I am gonna do all the things mentioned in the video. It sure doesn't look too pricey. Thanks man for a great video. thanks for helping others out!

that hose you capped off goes on the drivers side fender if you feel you can feel a nipple on the inside of the fender, it goes to you HVAC thanks for the video I like it I have 2001 s10 4x4

This helps me in a way, since I have a 1999 chevy trailblazer with a spun rod bearing that was given to me, and the transmission was able to be put in neutral and the vehicle pushed and loaded onto a car carrier, but after I had it awhile I wanted to hear the knock for myself and I just made a video of my freebee blazer, but the wheels are locked up, won't roll in the yard now, and with engine running that I can't get the transmission to do anything even when shifting,...but I didn't realize how much vacuum is on these vehicles, and below the battery tray, the rusted out battery tray, I have been removing and installing the battery numerous times, I suspect now that a vacuum hose somewhere is removed or that actuator below the battery is disconnected or damaged from battery removal and replace numerous times,...its important I work this out if I replace the engine with a remanufactured or used motor that I know what else will or will not work.....Its surprising how much vacuum lines are used, considering how much electronics were even on those late models. The battery tray is just eaten away, I have a new one, but the whole area around and below there is from mild rust to heavy rust, I may even have to wire feed weld a patch panel once I really dig around there with the remnants of the battery tray removed, and I had no idea there was a vacuum actuator there, jeese, maybe its best that way, ...easier to fix than fancy electronic solenoids, etc etc.

thank you,hell ya it helped.just had same thing happed to my boys 96 blazer.same line burnt thru .and had no idear how the vacume lines worked ,now i do.lol

thanks for your time brother, this helped tremendously. have a great one!

Definitely going back to these for my 5" .45

Hell yeah I'm having the same dam issue I've just watched the video. Hell yeah thanks man u do an awesome job

Yes on my 01 was the rotten hose by the master cylinder easy fix maby 2 minutes if you have hose I'd check that first .thanks for the upload

The vacuum line, you put a plug on, goes to a box (hidden) behind the ABS, (inside the side quarter-panel), only 6 inches away from the "T" connection. Thank you, #Adam_Hamrick for your video.

Thanks hope this is my solution.

thats crazy. 16 hours of tracing lines replacing cables and switches and shit. caped that bitch off n 4wd works. fuck that vaccum shit lol. thank you

I replaced this part as well as the actuator which was destroyed when transmission fluid leaked through the vacuum line. The new switch did not prevent the TF from leaking and it destroyed a 3rd and fourth actuator until I solved the problem by installing a check valve that allows vacuum but not fluid from the transmission. In order to revert to 2wd, I have to manually release the vacuum. I do this by having a dual ported check valve. I have a vacuum line extending out with a plug in it. I remove the plug for a second to release the vacuum after pushing the 2wd button.

Good explanation. Thanks

thanks man I just got mine for $300 but I need a new windshield and tires. I can hear it shift into 4x4 but the front tires still don't spin. I think it's probably the same problems you had. thanks alot I'm going to check right now

When that vacuum switch you had in your hand takes a shyt? It leaks transmission fluid up into the diaphragm & the transmission fluid rots the, diaphragm. I'm thinking it probably eats at the vacuum lines, as well? I'm going through this with the 4wd on my 96 Blazer, currently. I gotta get me that 3 hole vacuum switch. I already replaced the diaphragm. That shut my check engine light, off. I put a BADD switch in mine til I can get a NEW one. It's jammed all the way CLOSED to keep transmission fluid from going into my new diaphragm. I just still don't have 4wd, at the moment.

Subscribed because this video is excellent

THANKS ADAM.A WORLD OF KNOWLEDGE. I VE BEEN HAVING PROBS WITH MY 99 S10 4X4 WORKIN,NOW I SEE MANY THINGS TOO CHECK.I HAD ALREADY REPLACE MOST OF THE VAC LINES AN THE ACTUALATOR.NOW I M TAKING YOUR ADVICE AN PUTTIN MY BUMP AROUND RUST BUCKET OFF THE GROUND ALL THE WAY AROUND,BECAUSE IT SUCKS TO CHECK THE 4X4 5 TIMES A DAY IN THE OVERSIZED PARKING AREA 8 MILES DOWN THE ROAD.. SO UP IT GOES.. AN NOW WITH YOUR HELP AN THE HELP OF YOU PEOPLES COMMENTS. WHICH I WILL BE REFERING TOO ALL THE TIME INCLUDING YOU VID..

Adam thank you. I wish you lived in Alaska so you can fix my car I have a 2000 blazer and it’s stuck in four-wheel-drive I don’t know why

The vac line u was talking about at the 2 min mark, where does that start and end? Is it going into a tee in the transfer case?

Thank you so much very helpful

Thanks I have been looking for a long time for this video Did an engine and trans swap from a 2004 to a 2001 and my four wheel stopped working

Thanks adam was helpful

I got a fever.. oh yeah... the only cure.. MORE VACUUM LINE!! OH YEAH!!

Does it matter which vacumn line goes were from the gear box

The thing that you plug in / capped... It's called and goes to the " Vacuum Canister Reservoir ". I believe they changed it to the " Hidden Driver Fender " after 1996/98 on?, or if your " Relays " are NOT on the Passenger Side or in the Glove Box. If you see the Black Big Fuse Box / Relay under the Hood on Driver Side, then you know they changed it and it's " Hidden " on Driver Side Fender.

Since all tbe comments are 3+ years old ill add this for thr next guy (thankfully plenty added this years ago) but dont cap the tee lol, tbe hardline you see goes to hvac and where he capped goes to thr resevoir inside tbe driver fender behind the abs modules bracket (windshield side) lol. Dont cap.

Thank you sir!

The last thing you fixed, is that a vacuum check valve or just a spiller?

Ok so I’m confused, I bought a Sonoma with the dash button switch and 4x4 doesn’t work. And I looked under the battery and there is no diaphragm or mounting for it and it looks like it was never there. But it has all the valves in the front axle and on the transfer case and I have the original window sticker for the truck and it come with 4x4 from factory. Did some models come with a fully electric system?

Nice video! I’m troubleshooting my 4x4 now. I️ have no problem getting into 4lo but 4 hi only works after I️ disconnect the battery... any thoughts?

thx Adam.

Thanks for the video and by the way my 1999 Blazer just now is showing "Service 4 Wheel Drive" light on the dash. It will work for a short while when i just start the truck up in the morning then the Service 4 Wheel drive light will come on and then it will not change out of 2 wheel drive. Do you have any comments?

So what size hose would I need

My issue is I have a 99 Gmc jimmy and I just replaced the 4x4 selector switch cause the other one wasn't lighting up..My question is when I put it into 4hi or 4lo it engages and it disengage.But when I push the button the light doesn't stay solid but it flashes and do know some vehicles are designed to flash.Now there is no 4x4 service light on either.Now is my truck designed to flash when in 4hi ?or could this be a bad switch or something else??I just bought this jimmy 2 months ago and it was well kept but this issue bothers me..Please help me if you can..

What dose the melted vacumline you had on the passenger side under the truck go to

So i just bought a 98 blazer 4x4 dosent work and i know a few lines are dry rotted. So basically just replace all the vacuum lines and the actuator and the switch. And it'll be fixed right lol

Do you know what the RPO code is for front lockers on those trucks I have the exact same one

I love these trucks, my ZR2 is a 02 blazer, but the vacuum operated 4wheel drive absolutely suck, just a crappy design. That alone is the only complaint I really have with it.

Adam where does it get the vacuum from?

What code did your scanner read?

Can you tell me where the 3 lines from the switch on the transfer case go. I have one hanging and dont know where it goes.

Just wow! I reeeeplaced errrythin and den dat thang wurked. Lol

Glad you guys like working on these things. Fixing to crush mine

Does that thing have front lockers I heard that those trucks do the ZR2 I know they have rear

Who are you ?? You are amazing ❤️❤️❤️🌈

98 blazer, push buttons work, you can hear my transfer case lock in, BUT no 4x4. What could be my problem Adam?

Im having problems with my s10 it says it's in 4wd but it's not working

My Truck has Whistle right over the transmission or transfer case....I Think it is leaking??......No 4WD......not yet...

what size are those vacuum lines Adam?

are you from tennessee lol thanks for the info i have same model

Good jop

My s10 has a hard time getting out of 4 wheel drive

damn good video very instructional and through . Detroit andy fb Florence ms . peanuts auto

This is about the shittiest way I've ever seen to engage 4x4. This was deliberate by getting rid of the reliable physical link to the axle via a lever they would sell parts when something would always fail. Vacuum lines are a terrible way to actuate anything because they rot out. If you want to get rid of the vacuum and actuator headache just install a manual cable pull to give yourself a direct mechanical link to the axle.

Good video,next one, don't spit"" Not good !!!

What about your heat doors that is where that goes