I took my '00 SE to Jiffy Lube for an oil change and they pointed out some kind of dirty build up above the coolant in my overflow reservoir. He told me that it'* because my Thermostat is not working properly. (Of course he thought $57 radiator flush was the way for me to go - but, was stumped how that would solve a T-stat problem.)

I have no indication that my T-stat is anything but fine. I am interested in gathering facts so that I can stick them in the manager'* *** when I call him about it. What is that dirty build-up in my coolant reservoir? (Sounds like someone trying to make a couple of extra bucks to me.)

Thanks
ADD ON 02-16-03: My car was originally sold in October 1999. When I bought the car in October 2001 and it had 5K miles on it and the brownish stuff was in the boe a T-stat problem.)

I have no indication that my T-stat is anything but fine. I am interested in gathering facts so that I can stick them in the manager'* *** when I call him about it. What is that dirty build-up in my coolant reservoir? (Sounds like someone trying to make a couple of extra bucks to me.)

Thanks
Add on 03-08-03 : Got a call with apology from General Manager of the Jiffy Lube after I logged my complaint online with your suggestions. Received a free oil change and a promise for some retraining. Thanks to all who participated.

My only familiarity with dexcool is was in my 98z71, and I never saw any sludge in 4 years with it. I can tell you a thermostat is strictly a mechanical device, and it either works or it doesn't. It can't cause a chemical reaction. You already know this, but it would be nice to have a couple of our mechanics or our GM employee jump in here, then print out this thread and take it back to Jiffy Lube.

What does the sludge look/smell/feel like? Has the car had a mix of the typical glycol antifreeze and dexcool at any time? My concern is what this sludge may have done to the internals, especially the radiator.

If you haven't read the dexcool info up in Techinfo, read up on it. There'* identical info at www.bonnevilleattitude.com and the Rat may have more posted there now. Down in the Techinfo forum near the bottom of the index page.

Whatever you find out may be of use to others, so let me know if I need to add any info to that article.

My experience with Jiffy Lube and similar discount oil places is typically bad. The reason for this is the Manager. Some of them require their employess to show you color samples of the fluids in your car, then give you bogus info on what GM recommends for fluid change frequencies. I've burned a couple by simply pulling out my owners manual and calling bullshit. If you do this, do what I do, and call bullshit in front of other customers. It teaches them a good lesson, and others can get their warning that way. Deathrat used to manage a place. One of the good ones. Try to find a locally owned or better managed place to have your oil done. I'd normally do my own, but we have a really good one here. I take my own oil in (Mobil 1) and they do it all up for me. Besides, the Manager just bought a 97 SSEi, and I get extra attention now It'* nice to have a place say "it'* getting close, but lets wait til next time and see what it looks like" instead of trying to gouge me right away.

I was told the build up was stop leak that was added to all the cars from the factory. I guess GM is trying to cover its butt.

I would have to defend GM here & say the "Jiffy Lube" is full of doggy doo here! The ONLY car model to get "factory" coolant sealent "tabs" is the Cadilacs! Cadilace Division use different materials in their cooling systems than rest of GM. Without these coolant tabs, they will leak! :? So, either a previous owner or lazy mechanic has installed "tabs" in your system OR it'* been too long now that the DexCool has beeen in there & it'* ready to be changed out.

When I was looking through All Data there was a service bulletin about a build up in the coolant overflow bottle brownish in color. It stated it as a normal condition as there is a small amount of sealer added from the facory. I'll see Monday if I can find the bulletin #.

You talking about this one?
00-06-02-005 JUN 00 Engine Coolant - Contaminated Recovery Reservoir
As posted on ALL DATA for the 2000 Bonneville!

I have the same light brown residue in my coolant reservoir.

I assumed it was normal. It certainly does'nt have a lot of miles on it after 3 years, so I thought it might be a natural product of coolant degredation over time.
There is only enough to lightly coat the upper portion of the reservoir above the coolant.
Should I have the cooling system flushed :?: or simply clean out the plastic reservoir.

You know, I did notice that when I took the thermostat out to drill it, that the copper part of the thermostat was lightly corroded.
Do you think it was a galvanic reaction to the other engine metals :?: Maybe another sign that the coolant is going bad. :?:

Deathrat - Tell us more.

I'll get it from work'* Database on Monday!

If you're gonna drill a thermostat, start with a stainless steel thermostat body. Not a plated stat. I just drilled mine and ran some tests, and I plan to post some info on this in Techinfo. Can everyone running a drilled stat send me their observations on PM or email? I'd like everyone'* input on this!