Thread: 3.1 LIM Gasket Leak. What damage could already be done?

Hey all. Great site with lots of info. I searched on this but most of what I found was on the 3.8.

My son has a 2001 Pontiac Grand Prix, 3.1 engine. Took it in Thursday for tires and an oil change. Get a call with bad news. LIM gasket is leaking externally on both sides, and oil has mixed internally with the coolant. There is oil in the radiator and overflow reservoir. They said the used oil didn't look overly unusual, but it was discarded or mixed with other used oil? Talked about milkshake looking oil but I can't remember if that was an example from a previous car they worked on or this one. Maybe they were hiding something?

Also, there is a small diameter and short length hose from the front of the intake that is saturated with oilyness (from inside out--their words), so mechanic thinks it's been this way since well before last oil change. My son has taken it to a quick lube place for his past several oil changes and I'm sure they don't care or look that close.

They said they can replace LIM gaskets, all hoses, chemical flush cooling system, etc. but don't know how long the engine might last cause the damage may have been done already (improper lubrication due to diluted oil).
So no warranty. I stopped in to see all this in person.

The car overall is in pretty good shape, but needs some other work like the tires, front brakes, tie-rod ends. All in all the rest not a huge deal as these are going to happen sooner or later on all older cars. I do not have pics as it is still on their lift for the long weekend while I decide what to do, and didnt think to take any while there.

Is there any way to determine if the coolant is mixed into the oil? Which from what i've read could be much worse or fatal.

What possible internal damage has already been done due to diluted oil, and how can I tell?

Can I get your advice on what could be the future of this engine, what could be damaged already, etc. Also, if we dig into this, what else should we do while in there?

Until this issue popped up, I was unaware of this common problem with the LIM gaskets and never heard of Dexcool. Not sure of mileage but prolly well over 120,000 or more. We've had it for 2-3 years. I think it had a coolant flush a year ago?

Thanks for your help!

Originally Posted by 01gpgt01

If the oil is a milkshake color. Then yeah Oil and coolant mixed. Replace the LIM gaskets. Theres a chance the rod bearings can fail from it. After they replace the LIM, and put fresh oil in it run it for a day or two and then change the oil again. Using a good synthetic oil. Should be good to go

Is it necessary or advisable to replace the LIM itself, and or the UIM & gaskets? I've ran across threads like that on here, I think mostly w/ the 3.8s.

Thanks for your input!

carefully clean the manifold and ule be fine. replace both the lower and upper gaskets, change thermostat, change the oil, then change again in about two days, flush and fill the coolant. if your going to do the work, watch your torque settings

Originally Posted by musiknjoyr

carefully clean the manifold and ule be fine. replace both the lower and upper gaskets, change thermostat, change the oil, then change again in about two days, flush and fill the coolant. if your going to do the work, watch your torque settings

Thanks for the info!

Is this the engine where the UIM can warp and cause leaks? I'm not terribly familiar w/ this engine, and still have not seen the car since last Thursday. Wife & kid took it today to a shop I trust for a 2nd opinion / estimate. Tied up w/ work all day.