I'm searching the archives for additional ideas but am also posting here for quick feedback.

Engine:
95' v6 3.9 in a 2500 w/cast heads

Problem:
Got oil and coolant mixing
over heated from a blown hose then repaired hose, pump and thermo before test driving some more. Never ran in the red but as thermo rises I would shut it down.

Progress:
compression is near spec on evens but 50% on odds (head 1)
during removal of intake - the intake gasket was blown in 2 places
removal of head 1 - no blown head gasket & no obvious cracks & no sign of coolant or burn transfer between gasket seals


Additional Details:
- waiting for a crack and valve seal test on head 1
- removing head 2 to replace gasket just in case since I have it apart


QUESTIONS:
The intake gasket crack would only cause mileage loss & not much else correct?

Could a Bad valve seal cause coolant and oil mix?

Other then waiting for head/valve testing on head 1 and continuing with removal and exam of head 2... what else could I be looking at?

could I have strong compression in head 2 and still have a cracked block?

How can I test for a cracked block before spending money on the head?

 

Intake gasket can cause oil and water to mix, depending on location. Water goes through the intake manifold.

Valve seal should have no effect on oil and water mising. Would only allow oil into combustion chamber.

Heads are far more likely to crack than block. I would have both heads checked to be sure they are both good. Knowing on one and just hoping on the second one may be risky.

When it is back together, you can pressure test cooling system to verify that it is tight before cranking up.

 

What were your compression numbers?

A 3.9 in a 2500??? Really? Is that a typo?

 

It is the Van 250/0 body/model with a 3.9 but I posted here because I get quicker engine feedback. ;-)

low #s on head 1: were in the 55-75 (est)
high #s on head 2 were around 155-165

:-/

Knowing the blown intake could be and is likely the cause of the mix is the primary answer I was hoping to hear. I'm in the middle of rural east Texas with no large mechanic shops near so I am going from garage to garage the next few days to try to get a more experienced tester to look the heads over before putting it back together just to cover all the angles the best I can on the fix.

I appreciate all the feedback this post receives very much... I don't want to put it back together without having everything down that ya'll recommend before hand.

cheers.

 

Heads can be cleaned and magnafluxed to check for cracks. Any good shop should be able to do this.

 

Intake manifold gaskets won't affect engine compression numbers. If you are getting more than one cylinder below 100PSI, you have a serious problem. If that is on the side you did NOT yank the head on, you need to. If that IS the side you yanked, and you didn't find an obvious problem with the head..... it's rebuild time.

 

LIkely issue:
Valve rings could be the cause of the bad compression though....correct?
and the intake gasket....the cause of the oil/coolant mix?

Never ran the engine super hot so a block crack is very unlikely in this case.

Head results will be updated hopefully by Tuesday.

 

Valve seats could contribute to compression issues. When heads are checked, they should check/lap valve seats. They should be able to tell if seats or valves are bad.

Rings are on pistons, and could also be an issue for compression. But that would require pulling engine for overhaul. This is the "rebuild time" that HeyYou referenced.

 

Magnum Heads? If so, those are known for cracking...