Coolant in Oil vs. Oil in Coolant

I noticed today I have a leak from the radiator.  I then removed the radiator cap to check the level and discovered oil in the fluid.  Is this a head gasket issue?  What might cause this, and what should I do at this point.  What might I expect for cost to have the engine repaired? I have been considering an ls4 engine swap.  Am I jumping the gun on the swap idea or is it time to scrap this motor and go v8?  Any thoughts  would be appreciated.

Most likely it's the LIM gaskets leaking. It's an extremely common problem from a combination of plastic gaskets and old DexCool antifreeze. Worst case maybe you need head gaskets. You can find this multiple ways - a cooling system pressure test, or if that shows nothing a cylinder leakdown test. I'm guessing the cooling system pressure test will point you straight to the problem.

Will a cooling system pressure test work if I already have a leak in the radiator? Please forgive my stupidity but what is an LIM gasket?

LIM = lower intake manifold. The stock ones are plastic. google 'dexcool intake gasket' and you should be able to find more than you want to know about the issue.

If you already have a leak in the radiator, a pressure test will show you that leak but might give you clues as to the other leak as well.

Has this engine been overheated? Could be a warped head or some such... Good news is that these engines are a dime a dozen used in decent condition.

Been thinking about this..

Wouldn't the pressure in the cooling system (~16psi) overpower the non-pressurized oil flowing to return at the LIM's and push coolant into the oil instead fo oil into the coolant?

Another idea on this is that the facotory trans cooler that is within the radiator could have developed a leak. Trans fluid could be pressurized higher than the coolant, I'm not sure it it's over 16psi in the cooler though.

Quote :

Wouldn't the pressure in the cooling system (~16psi) overpower the non-pressurized oil flowing to return at the LIM's and push coolant into the oil instead fo oil into the coolant?

This is what I am thinking, too. I have a small LIM gasket leak. The result was coolant in the oil, and some residue on plug electrodes, but coolant itself seems fine.

1st post... I just inherited a '98 Riviera with 51,000 miles... Everything is pretty much mint as the last owner had kept it pretty meticulously maintained... the one thing that is concerning is that the coolant seems to be a bit milky... I've read that this could be due to contamination from oil or trans fluid, but the oil and trans fluid both look perfect.

Any ideas?

Thanks

kakaharoo wrote:

1st post... I just inherited a '98 Riviera with 51,000 miles... Everything is pretty much mint as the last owner had kept it pretty meticulously maintained... the one thing that is concerning is that the coolant seems to be a bit milky... I've read that this could be due to contamination from oil or trans fluid, but the oil and trans fluid both look perfect.

Any ideas?

Thanks

Welcome to the site

You can get oil in the coolant without getting coolant in the oil, and vice versa. The Lower Intake Manifold gaskets are probably the culprit. Those gaskets are probably the most common failure on a 3800 engine. They have since updated the gaskets, and it'll probably never happen again as long as you own the car if you have the gaskets replaced.

Thanks for the quick reply... Seeing I'm new to the 3800 is there anything else I should look for?

This car was owned by an old man that stored it during Michigan winters and it probably just sat all last year.

Thanks.

Just sitting is the worst thing for a car. Seals and gaskets dry up and crack. I just went through this with a different car I purchased. Gorgeous car, but tons of leaks from sitting.

Get the Intake Gaskets replaced, keep it maintained, and the car will last you forever. The 3800 is typically bullet proof. It's lack of maintenance that kills it. Even then, I've seen this engine run forever with everything leaking and extended oil change intervals.

Where at in Michigan? You found a low-mile Riv before me?!!!

Get that lower intake gasket and oil changed ASAP.

RED ALERT ASAP

Warren. 12 & Van Dyke. The car was owned by my neighbors brother in law, he died and I got it for a STEAL!

There are other minor issues... AC needs a recharge, passenger window isn't working, dings and scratches... but the coolant issue is the one that worried me the most... Someone else told me that it might be the trans cooler that's causing it, I guess it's time to take it to the shop to find out for sure...

If there's a Riviera meet up maybe I'll see you one day... I love this car. Timeless elegance...

https://i.servimg.com/u/f18/19/25/03/91/riv10.jpg

12 & Van Dyke!!!!! Lol. I'm at 12-1/2 and Ryan. You've probably seen my car around (the gold one).

Good buy, man. Find a good, reputable shop please. A shop that knows about this engine and these cars. There are WAYYYY too many hack ass shops in our neighborhood. If you need a recommendation for a aftermarket shop, let me know. The good ones are far and few between....

Whelp, Abaddon just scored a life long customer.

matt270avian wrote:

Whelp, Abaddon just scored a life long customer.

I'm not an aftermarket shop. Most people with cars that old aren't bringing it to the dealer....

Merged this post with a previous thread - please read from top. While it's possible a bad LIM gasket could introduce oil to the coolant, in my case the reverse happened: coolant got into the oil, because the coolant is pressurized. I got 246k miles out of my original LIM gaskets, and my coolant was not milky.

I agree the LIM gaskets are a weak point on this engine, but they can last a LONG time. You should have them replaced if you can diagnose a definite failure, but milky coolant doesn't absolutely mean oil is in there. Could be the coolant was never changed, or someone added tap water with contaminants, which causes corrosion. Could be someone threw a few stop leak tablets in there. My first move would be a flush with water and refill with fresh coolant mix, then check in a month to see if the problem returns.

Check your plugs for deposits or have an oil sample analyzed - that's how you'll know the LIM gaskets are bad for certain. Best of luck!

Thanks all.. Great info... I can see this forum will come in handy... Abaddon, I sent you a PM about finding a local shop... we'll need to meet up at Vivios one day.