I have had my 1999 3800SC into the dealer twice now to find the reason for a loss of coolant. It has 51000 miles on it. It is not driven daily therfore the 2 weeks between trips to the dealer. They have pressure tested, and examined the oil and claim they cannot find a leak. Both times the car was in they suggested the low coolant sensor should be changed for $171. They can't seem to understand that it is doing it'* job. The coolant was low! I refilled it so I could drive it to the dealer. FACTS: Only had to add about 1/2 quart to top off the radiator. Coolant was low in the recovery tank also (sucking air). Problem reoccured after 30 miles of driving. Further info, last night I idled the car until normal temp was reached and thermostat opened. Top rad. hose was hot and hard (pressure). After a short (3 mile drive) I returned to the garage, left it running and found the top rad hose hot but soft, no pressure? After it cooled the coolant was again about 1/2 quart low. Any suggestions how to find this leak. I understand the SC does not have the same intake maniford issue as the non supercharged version or am I wrong?

Sorry for being so wordy, just trying to give all the info I can.
Thanks

Wow...with no evidence of an external leak, and no coolant in the oil, you have to be ingesting it through the intake and burning it off. My first two guesses would be the Throttle Body gasket, where the coolant enters the TB, it may be leaking, and being drawn into the SC, or one of the 2 o-rings that seal the coolant passages between the SC and the Lower intake. It could also be a lower intake/head seal. If you pulled your SC, you'd get a good idea of where for sure. Ingesting coolant has a cleaning effect on the lower intake. You can pinpoint the leak by seeing what area is clean under there.

It'* not too daunting of a job to tackle yourself, either.

This doesn't, however, explain how it passed a pressure test. Are you sure it'* not leaking from the water pump weep hole? It could be blowing back under the car while in motion.

When I first bought my Trans Am it would use about a coolents resevour worth in a week. (back then I would put about 275 on it a week). I could not find the leak for about 3 months. I knew it was not burning it, and not putting it into the oil. Turns out that it was a crack in the coolent reservour seam. It is was in a spot that could not be seen, and it never made it to the ground. I discoverd it on a 102F day when the tank finally spewed it contents in my parents driveway. I replaced the tank and cleaned the engnine compartment and 3 years later it hasent lost a drop of coolent. Just a suggestion.

Jay

Actually Will there is no O-ring seals on a 92! Just the TB Base Gskt (P/N 24500166), as the 92/93 TB has a elongated passage instead in the TB for cooling.

I'm talking about the two o-rings between the lower intake and the SC. Not on the TB. Either the TB seal, or those two o-rings.

/completely edited, I was thinking of different rings a min ago

You can see around where I circled the yellow o-rings, I believe these are what will is talking about. And no they aren't WHERE I circled, I used this pic earlier to point out the temp sensors

Bingo. Thanks, Doc. I can see 'em there. I have another couple pics like that on my website. Do you have a pic of the TB and gasket by any chance?

Not of the gasket, but the TB yeah. Hang on a sec lemme round it up

Interested in showing him the coolant port in the TB base. To visualize where it may be leaking into the plenum of the Supercharger. I really think this is the most likely place on the L67....assuming he'* actually ingesting it.

How often have I been wrong this month? I may be due for a bad call.

Attack of the 50ft throttle body!


hmm...the pic was way bigger before! haha