My firing order is right, cylinder 1 on the middle on the distributor, cylinder 3 on the front and cylinder 5 on the back. My adapter is a micromechanic adapter. I did the compression test and that seems to be the problem cylinders 1,2,&3 all at 150 psi cylinders 4 & 6 at 145 and cylinder 5 got to 30 psi! I'm going to put a little oil in that cylinder and test again and will let you guys know.

 

If better with oil then rings. If not then valves or head gasket. Any water in the oil?

George

 

I put oil in cylinder 5 and it got the same reading, from what I read that means it's not the Piston rings. Is that true? If so then what could it be and how could I figure out what exactly is wrong with it? I am only the 3rd owner, when I got it a little over a yr ago it only had 165,xxx on it and I only paid $600 bucks for it. It has 203,xxx on it now but I've tried to take care of it. I've replaced front hubs, lower control arms, upper control arms and some other basic maintenance stuff while I've owned it,and I would get it back on the road asap.

 

How would I check if there is water in the oil? Just drain some out of it?

 

Just look at the dipstick

 

Okay last time I looked I didn't notice any, that was about a week or so ago, I will go look again and report back. Thank you.

 

Nope no water in the oil

 

From what you have told us it is not the piston rings - it would be something with a valve if oil in cylinder does not help. You can tell which valve is leaking by pressurizing the cylinder with an air compressor (when on compression stroke) and listening to where the air is coming out - either intake or exhaust. But I would pull that valve cover off and make sure both valves for #5 are operational and seem to go up and down a normal amount when the engine turns. If it has a valve itself leaking and you want to fix it, I would just price out a pair of rebuilt heads and install them (but be fore-warned, doing engine work on Blazers takes a lot of patience as everything is packed very tightly and quite inconvenient). Success depends on your level of expertise and determination.

Total cost to put on a couple of rebuilt heads should be around $500 for heads + gaskets + new TTY bolts and oil change if you do it yourself. But first you should finish the diagnosis by pulling the valve cover and watching the valve action to make sure there is not a problem with that. In the end, which valve is leaking is really a moot point - as either requires the same repair in the end. So pressurizing with air is of limited value other than to actually hear the valve leaking.

I believe George is trying to determine if a bad intake gasket (4.3s notorious for this) has leaked coolant into the crankcase. If that had been the case, the engine might take a lot more repairs than expected and would be best to pull it for repairs or replacement. Right George?? Heck, it might be better to pull the engine for head replacement anyways...… certainly can do a better job with Torque To Yield head bolts and an angle gauge when its on an engine stand. No matter what, always use the Felpro rubber/metal intake gaskets when going back together - they are pricey but worth it.

Alternatively you can get a used engine and switch over your intake and exhaust manifolds if there is any difference in them. Irregardless, always replace the intake gaskets. You would need a 2001-2005 Vin W or X engine because of the knock sensor type.

 

Yes, water in the oil to help determine if there is a bad head gasket. This is not definitive but another data point.

Les has the right approach to check the valves.

George