Leaking intake or head gasket?
 

Hey all,
I've noticed I've been losing coolant internally- no signs of external leaks and the dreaded white smoke in the exhaust. I assumed it must be a head gasket leak, but have heard this can be caused by an intake manifold leak also. I'm also not so sure it's a head gasket because the oil is not milky at all and is at its normal level. I'm going to test for exhaust gasses in the radiator and do a compression test to narrow it down, but was wondering if anyone had more surefire diagnostic techniques to narrow down the culprit? I love flow charts, if anyone has one on the topic!
Thanks for any help!

should probably mention this is a 1994 s10 blazer 4.3l vin W

Nothing helpful in the service manual.

Go with your plan for diagnostics. The 1st gens are not normally known for leaking intake gaskets but this is definitively a possibility.

Thanks error_401. Surprisingly no exhaust gasses in the cooling system. I did a compression check a few months ago and everything was perfect, but that was before I noticed coolant loss. I'm going to do it again, but if it shows nothing unusual, what would you think... Check out intake manifold and call it there, or keep digging down to the heads to make sure everything is good there also?
Once again thanks for the input, I appreciate it!

You have white smoke out of the exhaust when the Blazer is warmed up?

Then it could be an indication of leaking into the manifold or from a head gasket. If you can get by an endoscope you could have a look into the cylinders, especially the piston surface at the time you have all the spark plugs out for the compression test. Also have a close look at the spark plugs.

It really comes down to how far you are willing to go after that. Once you remove the intake, are you also going to replace the head gaskets? How to go about that? Engine out of the truck? Machine shop and full overhaul, or backyard replacement with all the risks?
Difficult to say. I'd go by what an endoscopic look would tell me.

Update: The piston heads looked ok. The intake manifold didn't look great when I took it off, but it wasn't obvious if that was the source of my troubles. I continued down to the head gaskets for the experience and lo and behold, there was a small but noticeable amount of coolant in the #5 cylinder. Not 100% sure if it wasn't just coolant leaking into it when I pulled the head off. Didn't notice any cracks in the block or head itself, so hopefully changing the gaskets solved the problem. We'll find out when I get it all sewed back up in the next few days.
Also my engine mounts were trash so I replaced those...what a pain in the arse!

Thanks for the input

Sounds like progress. Yes, you might as well fix those other things while it is all apart.

Keep us posted.

Just as I was putting the last valve cover back on I thought to myself, "Wow, I didn't break a single bolt". Immediately after I broke two bolts off deep in the head- and nowhere close to the 90 in lbs they were spec'ed to. Then I broke an EZ out inside of the recessed valve cover bolt. When I miraculously got that drilled out 4 hours later and went at it with another extractor, the whole unit containing the threads sheared right off. Guess I'm buying a new head. Looks like I'll be pushed back another week unless anyone has any leads on a donor head and lives in walking distance!

Man, do I know that story well.

Finally got a new cylinder head, except one of the valve springs is missing half a keeper. glad I noticed before I put the valve cover back on, but it's too bad I already snugged up the cylinder head. No parts stores near me have any keepers, does anyone know if it's a bad idea to use the keepers of the old valve springs?

You've put so much work into it, I'd say get the proper keeper as you don't want to go back into this for want of a mismatched part that caused catastrophic damage to your motor, even if the odds are slim of something bad happening. Waiting to get the right part will give you peace of mind and allow you sleep well at night. :)

BTW, good catch on finding that it was missing.

Just in case you did not know this, are you aware that you can replace the valve springs and retainers without taking the head off? You turn the crank until that cylinder is on the compression stroke with both valves closed and then you pressurize the cylinder with an air compressor using an adapter at the spark-plug hole. I once had to replace all of the valve stem covers for a 318 V8 once using this technique.

If you use the technique I described above by pressurizing the cylinder, be sure to install the distributor so that you don't lose your initial timing and have to make the ECM relearn the timing settings.