# 1- intake gaskets. # 2- possible oil cooler defective in radiator, if equiped, but should have oil in coolant. # 3- possible head gasket/cracked head or block. Best suspect is intake gaskets!! Very hard on the engine bearings if it's much coolant mixed with oil!! Have it fixed asap. Post results so others may benefit.
Is it consistant with lost of power and coolant coming from the exhaust.Condensation on warm up is normal from the exhaust but if coolant is coming from the exhaust and you have coolant in the oil plus loosing power,then it's a blown head-gasket.A pressure test on the cooling system or a copression test on the engine will confirm the diagnosis.
How does coolant get into the crankcase from a "blown" head gasket? I agree it will steam from exhaust but how does it get in the oil on a pushrod engine? If it were an overhead cam engine then oil under pressure is running through the head and may breach the gasket mixing with coolant. On a pushrod engine, the gasket would have to be split at the point where the drain back oil and water jacket flow are close to each other, then you get oil in coolant as well. It's not getting by the pistons! A COMBUSTION leak test will confirm a BLOWN head gasket. Think about it! Intake gaskets on the other hand, will leak coolant straight into the crankcase! They then get replaced during the head gasket replacement and the real problem is fixed by defalt, everyone assumes that the head gaskets must have been the problem.
I am not saying it is not possible, just not as likely as the intake gasket.
The coolant goes through the head and the engine-block by way of the passages that are lined up where the head-gasket separates the head and the block,unless of course the chevy subarban is put together differently to any other engine.So if the gasket is blown, wouldn't the coolant and the oil-passages leak into each other? I was trying to understand your response about the intake gaskets causing the problem.Do you mean the intake-manifold gaskets'? I trust you won't mind explaining that for me.If it is transmission oil that's in the coolant and the radiator has a built-in trans. cooler then the cooler could be leaking. We agree on that.But distinguishing whether it is engine oil or trans. fluid may not be possible.
On 99% of BLOWN head gaskets, compression has cut or blown a path to the water jacket that is right next to the sealing ring at each cylinder.
This is what causes steam from exhaust as coolant enters the cylinder and is burned! This is also what puts compression in the cooling system and pressure on the radiator etc. A combustion leak test detects CO in the system which can only come from the combustion chamber, not the oil or coolant passages in the gasket! Now it is possible for the head gasket to simply deteriorate between those passages, but not likely. Coolant flows through the intake MANIFOLD gaskets and is the most likely cause of coolant in oil as just below the intake MANIFOLD is a direct path to the crankcase, where the engine oil is! On engines that do not need coolant flow through the intake MANIFOLD, if coolant is in the oil it is almost always the head gasket! An example of this is an inline engine.
Hi Pushrod, So,if I understand correctly you are saying that when a head-gasket blows, coolant does not always get into the oil passages,only sometimes.? I don't remember ever learning before that intake-manifolds have a coolant jacket around them but I know that the manufacturers are always inventing new things on different models.I remember many years ago I owned a Hillman Imp and when the head-gasket blew coolant was coming from the exhaust.The engine had an aluminum head and it kept blowing the head-gasket,so I finally sold it to a small garage to use for other parts,because he specialised in Hillmans.I appreciate you taking the time to explain and I hope I understood correctly. Thanks, Frank
No problem frankie, yes there is coolant flowing, through the intake manifold, from one head to the other ie thermostat in the center of the intake.
Now as i stated it is posdible for a head gasket to allow coolant to flow into the oil but it is kinda unuaual on a pushrod engine. However on a overhead cam engine, oil is under pressure as it passes through the head gasket and therefore is more likely to breach the coolant/oil passages. It's just that the first thing that comes to mind when coolant is mixing with engine oil that it's a head gasket problem.Been that way for years now. That's what i was always told but it is not a given at all! I think that a lot of head gasket replacements could have been avoided by just replacing the intake manifold gaskets. When the head gaskets are replaced, then so are the intake gaskets, which in turn fixes the actual problem it was to start with. I think that's how it got started!
I am sure there are some that will disagree until the cows come home, but that is just what I have seen over the years. Your answer was a good one, it is entirely possible the problem is indeed a head gasket! Always keep an open mind! Anything is possible. I have been doing this for a looong time, still learning.