Hey everyone new to the thread as well as to the s10 blazer. I have recently inherited a 92 S10 Blazer all in all in pretty good shape all things considered. The engine has been rebuilt a few years ago (8 maybe 10?). Either way here's the issue. My father in law drove it one day and ended up having a crazy burst of steam. He's not the most car aware person so not sure if he noticed it overheating. Got it back to my garage, and checked the oil and noticed the milkshake (oil and coolant mixing). So I drained the oil/AF (10 litres worth) drained the rad, pulled the plugs and changed the oil filter. Ran a few rounds of oil and turned over a few times to flush out the AF. Plugs are still out and I also sprayed a bit of oil in each cylinder to help prevent rust.

I ran a compression test and all cylinders had good compression and all within range. I also ran a coolant pressure test which held for a few and then slowly went down.
This leads me to believe that it's a lower intake gasket. From the research I've done, it looks like it's a common problem with these 4.3L vortec engines. Was hoping to get someone's advice on this as well as what I should do next? I really want to keep this truck as a project car so any help would be huge!

 

Either way, you're pulling the intake. Best bet is buy new gaskets and go through it. My guess based on your explanation is head gasket.

 

I believe the bad lower intake manifold (LIM) gaskets were more of a problem in the latter half of the 90s 4.3s. However, if the motor was rebuilt using one of the poor quality gaskets, the LIM could be the problem. That you had antifreeze in with the oil is a consequence of a bad LIM gasket. However, I guess a bad head gasket could be the culprit too but I would have though your compression would not have been good on at least one of the cylinders if that was the case.

How long was the motor run after the leak? I've heard stories that the crank bearings can be ruined super quickly if there is a big leak of coolant into the lifter valley. You might be lucky though and dodged that bullet.

I recently learned that my local Autozone parts store has a loaner borescope. If you want to do a full diagnosis before tearing into things, you might see if you could get hold of a borescope and check if you see coolant in any one of the cylinders. That would help remove any uncertainty. I think Harbor Freight has them too.

That all said, just as Blazersaver73 said, you will be needing at least to take off the LIM no matter what.

Whether you install head gaskets along with new LIM gaskets, be sure to use the upgraded LIM gaskets from FelPro that have the metal frame and not the plastic frame.

Look for threads on the forum that describe how to do the LIM gasket replacement. There are a few tricks to make the job easier.

What I wish I did when I replaced my LIM gaskets was to get some studs to temporarily install in the heads to help guide the intake into place.

Good luck and report back what you learn.

 

That's a good tip about the studs or guide pins. Guide pins allow the intake to be positioned correctly, so the sealant on the block does not get smeared.

If you buy new bolts for the intake manifold, guide pins can be made from the old ones. Cut the head off the bolt, give the edge a bit of a taper, and then cut a slot into the top of the pin so it can be removed with a screwdriver.


Guide pins.

 

Thanks everyone for your help! After finally moving and getting somewhat settled I’ve been able to get some work started on the blazer. Here’s some pics of the intake so far in the link below. Hoping to take the head off this weekend. Any other tips would be greatly appreciated!

Pics and videos of LIM

 

weird seeing you here, I didn't think I would find you here on this forum too , anyways i gave you some advice there that might be helpful