Thread: Coolant leaks

Yes it is pretty common to have the intake gaskets leak on a 3800. The stock gaskets are plastic but I think the "new" style that gm sells are aluminum, but I think you can still get the plastic ones if that is what you prefer. I my self use that aluminum ones. If are are worried that they might be going out just check your oil and see what color it is. If it is black or dark brown that is normal, but if it is a light creamy brown then your intake gaskets are leaking. I just bought a 99 regal with the s/c'd 3800 in it and it has 122K on it and I replaced the intake gaskets just because I know they have a bad reputation and they were still the stock ones. They weren't leaking but they would have been real soon.

There are the LIM (lower intake manifold) gaskets and the one under the supercharger. I would think you could do it yourself, it is relatively simple. There might be a write up around here but I am not sure. The main thing to remember is to change the oil right after you are done (whether or not you start if first is up to you I guess). The reason you need to change them is because when you remove the LIM you will dump some anti-freeze into the oil. I think it cost me close to $100 for gaskets.

There is a writeup for the naturally aspirated engines over at North American Impala Owners Association , but you have to be member to view it. I wrote it.

Here are the lower intake manifold gaskets, aluminum style. You will be replacing all four pieces here (the end pieces are rubber, and usually aren't what leaks). This part is the same between all series II and series III 3800s (SC'd or not).



I wasn't leaking coolant into my oil (that I could tell). I had a slow leak of coolant running down my bell housings. More a dark area than a wet spot. After fixing the gaskets, the dark spot disappeared.

Here's a pic of what I saw that made me want to repair the gaskets: