coolant leak around intake manifold?
 

99 Bonneville, 3.8 non supercharged, 55,000 miles.

Took girlfriends car into shop for oil change, coolant flush and tire balance and rotate.

Picked up car, shop said coolant was pretty low, and to watch for leaks.

Drove it home, parked it for 2 days.

Yesterday noticed a small puddle of coolant coming from drivers side of engine. Opposite water pump. ( I had noticed a few occasional drips from that area in the past, but it was only occasionally and nothing that seemed to be getting worse or happen all the time.)

Opened up hood, popped off plastic cover and noticed coolant pooled up on exhaust manifold and all around intake manifold gasket area. Area right where thermostat is located is dry.

Went back to shop to ask if they noticed anything weird and they said no, just that it was low on coolant, told them what I found and they said it was a common problem for the intake manifold gasket to start leaking on the smaller engines and occasionally on the 3.8's. Asked for a quote on what i described and I got $320.

Questions:

1. Has anyone else had a problem like this or heard of it? I've never seen water leaking from around bottom of intake manifold.

2. It looks like a pretty straight forward job to replace myself. Is it fairly simple and is there anything I should be aware of before I start?

Thanks!

it could be one of two things the T/B gasket could have started to leak or the Upper intake has failed.

DO NOT DRIVE THE CAR.

If the upper intake has failed and you try and start the car, and drive it or ever let it idle, it is bad very bad. The T/B gasket change is a rather easy and simple replacement feature. Could you please describe or give any more info that you have to fruther diagnose the loss of coolant issue

does it look like there is coolant dripping down from the throttle body area or does it look like there the coolant is leaking ontop of the block??

Drain the oil immediately. Like right now, even if it's 2am. If the upper intake manifold has failed, and coolant has entered the oil pan, it can rust the bottom internals in the engine.

Does the oil on the dipstick after running look contaminated? Milky? Read the Vin K Techinfo articles.

Those vin k articles are great! thanksonce again

the oil is brand new and looks fine, they just changed it same time as coolant flush about 3 days ago.
I drove the car max 2 miles home from the shop and it has not been started since.
mechanic said nothing about oil looking milky or anything.

I borrowed your engine picture to show where moisture is, just keep in mind, I don't have the turbocharger, just a black plastic cover covering the throttle body that bolts to intake manifold. Most of the coolant is in the back corner nearest drivers seat on the exhaust manifold.

http://www.billrae.com/engine.jpg

that is most likely the T/B gasket leaking. It is a simple fix, If you do a search you should find some good info

Re: coolant leak around intake manifold?
 

Occasionally?? From what I learned on this forum a 3800 might occasionally not leak. That is a pretty common problem from what I have learned. I just did mine a couple of months ago, but I had twice your milage. I replaced the upper plenum and gasket as I assumed the plenum was a victim of the infamous EGR "stove pipe" burn through. As it turned out it was not too bad. I machined a new stove pipe with a .050 clearance so it no longer touches the plenum and sleeve to prevent the problem in the future. The biggest problem I found was the TB gasket that is molded to the plenum was pretty flattend and was leaking much like yours is. The one bit of advice I can give you (if the '99 is like the '96) is don't even bother trying to remove the TB from the plenum til after you remove the plenum. You'll see why.

man the more i read the more i want to puke.......

i see no signs of breakdown on the outside of the plastic, looks strictly gasket to me, but will only know when i get it off.

You won't see any signs externally. I don't think you have enough miles for that though. yours sounds more like a TB gasket. I stopped mine for about 6 months and then slowed it to a trickle with the GM cooling sealer suppliment tabs. 4 tabs in the radiator will buy you time if you need it.

Ok, let's clarify a few points. First of all.....SUPERcharger. :lol:

Second, Bonnevilles aren't prone to leak in general. The 95-98 non-supercharged engines are prone to failure of the upper intake in the EGR inlet port area. It's rumored that 99 had an updated design, but keep an eye on it anyway. Yours does thankfully sound like a TB gasket leak. An hour fix for 10 bucks. Use an inspection mirror to see if it's dripping off the bottom of the plenum/TB union while idling hot.

ok, thanks again and sorry about the turbo charger slip.... :lol:

will let you know what i find.