2001 GMC 5.7 vortec / coolant in the oil / bad intake gaskets or bad head gaskets?

[Ohighway]

2001 GMC Savana, 5.7 vortec motor, 159k miles

Engine was beginning to lose small amount of coolant, but no external leak, no oil contamination or oil level change.

Brake lines failed, vehicle was parked, and was started periodically to keep battery charged.

Went out one day to start it and coolant reservoir was half empty. Checked oil , and it was at proper level and no contamination. Added coolant in reservoir, started and ran vehicle for 20 minutes....no problem.

Went out several weeks later to start vehicle. Pop hood and check coolant reservoir. EMPTY. Check oil and.....level way too high with the dreaded milkshake.... coolant contaminating oil.

Today I drain the contaminated mess, install a new filter and fill with fresh oil. Open radiator cap and add distilled water. Start vehicle and let it run without radiator cap. Coolant system is not contaminated with oil, and I am not getting any bubbling in coolant that would indicate a pressure leak from a head gasket problem.

After running for 20 minutes or so, (radiator cap still off so coolant system will not build pressure) long enough for it to come up to proper temperature, I shut it off and check again. Oil at proper level with no new coolant contamination.

So based on all the evidence I'm thinking intake gasket leak (when coolant is under pressure) , not head gasket problem.

Your thoughts?

 

[Old Ears too]

Yeah, sounds like it has a coolant leak that is not going into part of the pressurized oil system.
I had a BMW once that had a 'genetic' head problem where the head cracked and coolant leaked into the oil system up on the top of the head.
I used stop leak to fix it for a short time, but eventually ended up replacing the engine with one from another car which had been wrecked.

 

[D_Zoot]

Intake gaskets failures, causing coolant leaks into the crankcase, were very common on this engine. Headgasket failures are not very common and headgasket failure modes are usually leaks into the combustion chamber, not leaks into the crankcase. Your observations support an intake gasket fault.

The intake gasket is comprised of a plastic carrier with rubber seals embedded in the plastic. The plastic is the problem, it becomes brittle and cracks. The culprit is thought to be a chemical incompatibility between the original Dexcool formulation and the plastics used in the gasket carrier. The replacement gaskets, both OE and aftermarket, are much improved and won't exhibit this failure again. Some will suggest replacing the Dexcool with green coolant when you replace the intake gaskets, but while the Dexcool deserved it's bad rep in it's early days, current formulations don't have the issues the early formulations did.

I'd go ahead and replace the intake gaskets and change the oil again. Once apart, you'll probably see where the gasket has failed. While you are at it, look and see if you have the heater hose "quick disconnect" fitting on the RH corner of the intake, if you do plan on replacing that too, it's a coolant leak waiting to happen.

 

[quaddriver]

its a tear down. cannot avoid it.

if you love the vehicle, its a removal and tear down, including the bottom end. the coffee with cream plugs up the pushrods and no oil gets to the heads - which is restricted anyways - and failure is imminent.

I have *never* seen a mixed out motor, without pushrod clogs. they dont get hot enuf to re-flow the goo before it is too late.

why the bottom end? you really need to replace the rod bearings and roll in new mains. std size will do. then oil it with 0-20, start, idle, gently run, then change it to whatever gm recommends for that year.

thats the poor mans way of resurrection.

there are embossed gaskets for the intake that are way better than stock, and almost any felpro head gasket is better. indian head or not...thats optional.

are the head bolts ttys or standard? follow ALL recommendations for torquing - oil threads, sealant under heads, 3 steps up to max torque then 3 laps at max

 

[Ohighway]

Intake gaskets failures, causing coolant leaks into the crankcase, were very common on this engine. Headgasket failures are not very common and headgasket failure modes are usually leaks into the combustion chamber, not leaks into the crankcase. Your observations support an intake gasket fault.
.......
I'd go ahead and replace the intake gaskets and change the oil again. Once apart, you'll probably see where the gasket has failed. While you are at it, look and see if you have the heater hose "quick disconnect" fitting on the RH corner of the intake, if you do plan on replacing that too, it's a coolant leak waiting to happen.

I was gonna go out and change the oil and filter again today. Perhaps run some seafoam through it to help flush the contamination? Amazingly the oil looks fairly clean just from that initial change.

its a tear down. cannot avoid it.

if you love the vehicle, its a removal and tear down, including the bottom end. the coffee with cream plugs up the pushrods and no oil gets to the heads - which is restricted anyways - and failure is imminent.

I have *never* seen a mixed out motor, without pushrod clogs. they dont get hot enuf to re-flow the goo before it is too late.

why the bottom end? you really need to replace the rod bearings and roll in new mains. std size will do. then oil it with 0-20, start, idle, gently run, then change it to whatever gm recommends for that year.

thats the poor mans way of resurrection.

there are embossed gaskets for the intake that are way better than stock, and almost any felpro head gasket is better. indian head or not...thats optional.

are the head bolts ttys or standard? follow ALL recommendations for torquing - oil threads, sealant under heads, 3 steps up to max torque then 3 laps at max

Well with this thing having 159k miles, being 18+ years old, and having other issues (broken power windows, rusty bumpers, cracked windshield, needs some front end work) , plus the fact that I'm not going to be doing the work on this one (full size vans are a bitch)...... there's only so much $$ I'm willing to throw at this. If it's too expensive to repair then that money will instead go towards a replacement vehicle.

BTW, wouldn't clogged pushrods have announced themselves yesterday when I ran this thing for 20+ minutes. Seems the clatter would be obvious ??

 

[Old Ears too]

Since it sounds like the truck is on its way out, why not try some stop leak too?
I think with the sea foam and oil change after that you'll find out whether or not you'll want to keep it around.
I'd put the sea foam in it before changing the oil. A little over fill won't hurt if you're not running it hard. Then the oil change will be clean oil after.

 

[quaddriver]

I was gonna go out and change the oil and filter again today. Perhaps run some seafoam through it to help flush the contamination? Amazingly the oil looks fairly clean just from that initial change.





Well with this thing having 159k miles, being 18+ years old, and having other issues (broken power windows, rusty bumpers, cracked windshield, needs some front end work) , plus the fact that I'm not going to be doing the work on this one (full size vans are a bitch)...... there's only so much $$ I'm willing to throw at this. If it's too expensive to repair then that money will instead go towards a replacement vehicle.

BTW, wouldn't clogged pushrods have announced themselves yesterday when I ran this thing for 20+ minutes. Seems the clatter would be obvious ??

no really, the clatter is from valve clearance issues, which would be the lifters pumping up or not. it will take a bit of running for the ball ends to gall in the rockers - it might have already, and these things will run with vastly reduced lift, just way down on power. but you are right, if its a basket case, 17 years old...demo derby time you dont use coolant anyways!