intake gasket failure diagnosis

[jcweis1]

I just bought a 2004 supercharged 3.8 with 71,000 miles that runs bad. The coolant was brown junk and the radiator filler tube and cap was full of thick gunk. I flushed and replace with the green all vehicle coolant. Did not see any oil in the drained coolant and did not see any coolant in the oil when it was changed.

I suspect it has failed intake gaskets and it does have the black gaskets or bad head gasket or head.

Can intake gasket failure show as low compression on a compression check?

I do not know any history on this car and do not want to do intake gaskets and find out it has head or head gasket issues.

Is there any tests that can be done to know if the intake gaskets are bad. Don't know if it is using coolant since I just bought the car.

[J Wikoff]

Whether it's burning coolant or not, I'd replace the plastic LIM gaskets with the metal ones. Issues with the plastic ones are frequent enough that it's a good preventative measure to take.

If they were bad, it would not show up as a compression issue. A bad head gasket probably would. The cooling system can be pressure tested.

It just sounds like the coolant was probably original and sludged up. That used to be an issue with Dexcool.

[jcweis1]

Thanks - I will do the compression test and eliminate any head gasket issue before tearing down to do the intake gaskets.

Will leaking intake gaskets make it miss at idle and throw misfire codes making he check engine light flash?

[J Wikoff]

It could if the coolant is interrupting combustion.

FYI, 3800's rarely have head gasket issues. Like, super rare. LIM gasket or UIM issues present similar symptoms and get misdiagnosed a lot and may never be realized if inadvertently fixed when replacing head gaskets.

[jcweis1]

Do you think a failed pressure test on the cooling system is enough to justify doing the intake gaskets without a compression test? Never have done a cooling system test. What do I look for?

[J Wikoff]

If you aren't losing any coolant, I probably wouldn't worry about doing the pressure test. IMO, my plan would be to replace the LIM gaskets with the metal set, and remember to get metal coolant bypass elbows while you're at it. And if you are going to replace the LIM gaskets anyway, a coolant pressure test wouldn't tell you as much as a compression test would.

[jcweis1]

Thanks! the compression test it is and if good will do the intake gaskets using the metal ones.
Do you have a link for a good step by step procedure on doing the intake for a 3800 with supercharger?

[J Wikoff]

There's on in our Techinfo for the NA 3800, and it wouldn't be much different, but for specifics on a Series II SC, someone else will have to answer. I don't have one.

[ThisGuy]

first off if u still have that nasty oil in the car DRAIN IT NOW, and when you get the LIM off wash the the block out with fresh oil to try to dilute/flush the old oil out. when coolant and oil mix they become very acidic and it thickens the oil and will mess up all your seals and then you will just have massive oil leaks.

second a compression test only kind of tells u that there is a possibility of a head gasket leak, because u can lose compression past bent or unseated valves, and bad piston rings will let compression seep into the crank case. also if u have a misfire then all the unburnt gas in the cylinder will wash the oil off the cylinder walls and give you a low compression reading. so u have to put a SMALL amount of oil in the cylinders to seal the rings.

u can try pressurizing the cooling system to check for a leak but you have to make sure that your coolant elbows or coolant lines arent leaking externally...but with plastic LIM gaskets and coolant in your oil it would be best to change the LIM to an aluminium one (and aluminium elbows)

does your car have any stored codes? I literally did my LIM gaskets 2 days ago. they didn’t fix my misfire issue but deff help with my coolant loss (misfire was a bad coil) ive got a couple pics http://s483.photobucket.com/user/Dong_Johnson/library/

[Backhoe]

When I bought my LSS the LIM the job was performed pretty quick, not because it was showing signs of failure beyond a brown line in the expansion tank, but because its a known failure, class action style failure, and I just want to run my L67 long time. $200 (Canada) approx with metal gaskets for sooo much piece of mind, well worth it in my book. A bunch of the $200 was for associated gaskets, o-rings etc that I did at the same time.

I also performed mine on an S2 using the tech info article.