3.8 intake coolant leak

[Cal_in_Seattle]

You can buy NEW intake manifolds from a company that advertises on E-bay. You'll save a bundle over dealership cost.

But if your intake manifold started leaking coolant into the engine then it is a really bad thing. My 1998 Bonneville SE wore out a rod bearing shortly after the intake manifold leak. The engine only has 59,000 miles.

Gundy's Auto in Bellingham WA has inexpensive Bonneville engines. Bought mine for about $950 with shipping. Replacement motor only had 6,000 miles!

[MRWSM]

Anyone have an opinion on putting on a cooler thermostat of about 180 degree. I did this to my 2000 Bonneville. My thinking is the slightly cooler temperature would put less stress on gaskets. I have done this to all my cars when I first get them, I think it helps, never had a gasket go on me.

[mayo302]

The 180 degree thermostat is a really bad idea; it won't reduce stress on the intake. The intake melting is due to the EGR temperatures. Running your car with the 180F thermostat in there will cause it to run rich all the time; the car will dump more fuel into the mixture to try to warm up, increasing your emissions, decreasing the fuel economy, and potentially damaging your catalytic converter. Your heater will also have decreased performance in the winter.

[Jrs3800]

First this post is older than dirt and we have all learned a lot in 5 years... As well there are better solutions for this problem..

I'd like to know how 15F makes such a huge difference? I have 4 GM 3800's all of them have a 180F thermostat.. On all of the cars I have 30-32 MPG has been easy to come by... I have done as much as 33 Mpg with the 180F thermostat with a Large Bonneville filled with people and luggage, all of this with the 3.06 Gear ratio... For me there was no difference at all with the 195 vs 180... That goes for all of the 3800's I have..

And why is it that certain GM engine come from the factory with a 180F thermostat...

If you were looking at a Sonata with a V6, a 180 Is stock, 170 is the alternate..

I have had no running issues, oil burning issues, no fouled plugs, no running rich...

If you had dropped from a 195 to a 160F yes that would be an issue unless you programmed for it..

[mayo302]

I wasn't meaning to insult you for the idea, and I know it is an old thread. I just accidentally stumbled upon it as a result of a google search, and I wanted to make sure the information was as correct as possible in case someone who didn't know much about cars came across it.
Yes, 180F or even lower is stock for some vehicles; typically 190-200F is stock however. Are you going to drop 5+mpg by changing it by 15F? No. Will you lose some fuel economy and put more unburned hydrocarbons through your catalytic converter and out the exhaust? Yes. I'm sure it's worth a significant change; just because you got 33 mpg highway with a loaded down car doesn't mean you couldn't have gotten 35 mpg or higher. (we all know weight has little to do with highway fuel economy)
Going to 160F from 195F, as you said, will become significant even to someone who doesn't monitor their fuel economy closely.

With regard to the original post, however, there is almost no way running a colder thermostat will reduce the likelihood of the intake leak or reduce stress on the plastic components.

[Jrs3800]

No insult at all..

I agree with you on certain points.. The reason for a 3800 having a 195F thermostat was for emissions purposes... The 1995 Series II 3800 V6 could actually be called a low emissions vehicle.... So I do agree that the lower temp will cause slightly more emissions, but again all 3800's are known to be very clean running engines..

The cooler thermostat can help to a certain degree, not enough to stop or change the EGR port in the upper intake from getting cooked.. 2 of the problems were that Nylon66 was only designed to withstand 500F, as well in the earlier designs the EGR Tube actually touched or almost touched the EGR Port wall which cooked the Nylon66 over time creating a rupture that most will see as a head gaskt problem when in fact its the upper intake rupturing allowing the engine to ingest coolant..

what we call APN or ineedparts( their new name ) has an upper intake that we like, the intake uses a stianless sleeve in the EGR port, as well the kit come with both reduced diameter stove pipes, it will fit the larger or smaller bore of the lower intake.. Older years had the larger bore and newer years had the smaller..

Along with that we also recommending replacing the lower intake gaskets with the GM aluminum gaskets... Both of these together will keep the 3800 going for a very long time to come..