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1999 Pontiac Grand Prix coolant leak

Tiny
JBENNETT5847
  • MEMBER
  • 1999 PONTIAC GRAND PRIX
  • 3.8L
  • V6
  • FWD
  • AUTOMATIC
  • 211,210 MILES
I was driving around earlier in my Pontiac grand prix gtp supercharged and pulled into a store. When I got out there was grey smoke coming out of the hood and the radiator was making a "pssshh" noise. When I looked at it the overflow tube was leaking from rubbing against the supercharger belt. I replaced the hose and zip-tied it down, yet there is still a leak coming from around the coolant storage and I cant seem to find it at all. The engine is a 3800 series 2 V6, the standard setup for a Pontiac grand prix GTP and hasn't had an issue until this point, I noticed that the belts have started squeaking at 1500 RPMs and higher and the engine temp generally doesn't go up when its in that range of low rpm's
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Tuesday, September 2nd, 2014 AT 9:11 PM

13 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
The belts may be making noise due to coolant getting on them. As far as the problem, is the engine overheating?
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Wednesday, September 3rd, 2014 AT 5:07 AM
Tiny
JBENNETT5847
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The engine is still overheating once it reaches those higher RPM's. I also noticed that there was a plastic clip on one end that looks kind of like a one time use clip. Its plastic and has ridges that lock it together. I felt it and noticed that there is coolant dripping off it but it doesn't seem like a large enough amount for a whole container of coolant to drip out in 20 minutes
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Wednesday, September 3rd, 2014 AT 6:29 AM
Tiny
JACOBANDNICKOLAS
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As far as the leak, it could be that the system is low on coolant and is drawing it back into the engine. It could be that when it overheats, the coolant is leaking from the overflow. Now I have questions. First, have you checked or replaced the engine thermostat? Are you certain there are no other leaks other than the overflow jug? When the engine overheats, do you hear the coolant boiling or is there steam from the cooling system? Does it overheat when you are at highway speeds?
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Wednesday, September 3rd, 2014 AT 8:37 AM
Tiny
JBENNETT5847
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I have not checked the engine thermostat, but when I hold my hand over the engine it is incredibly hotter and does sometimes steam. Later today I'm going to replace the plastic clamp with a metal one and put more coolant into it since I noticed it was leaking from there. I cannot exceed high RPM's or speeds of 40 mph without it heating up very fast, but in lower speeds and RPM's it will sometimes stay consistent while there is a decent amount of coolant in it. I did check to make sure that it really was the new coolant leaking from it and both colors and smells matched.
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Wednesday, September 3rd, 2014 AT 9:10 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
The odd thing is that most cars don't overheat at higher speeds, but rather they do at lower speeds. Check to make sure there is no coolant mixing with the engine oil. If there isn't, the next thing I would do is either check the thermostat or replace it. It's less than a 10.00 part.
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Wednesday, September 3rd, 2014 AT 7:54 PM
Tiny
JBENNETT5847
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There is no more coolant leaking. Yet when I turned it on one of the belts was still squeaking and there was white smoke coming from what appeared to be one of the seals from the engine for approximately 5 seconds and the thermostat is working fine. I checked the oil aswell and its just the same color and same amount as it was before. I heard of a similar instance where white smoke came out of an engine and that one had to be replaced
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Wednesday, September 3rd, 2014 AT 7:59 PM
Tiny
JACOBANDNICKOLAS
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What was done to check the t-stat? Can you upload a pic for me to see where the white smoke is coming from? As far as the belt, are you certain that it is tight and the tensioner hasn't failed resulting in not turning the water pump fast enough?
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Wednesday, September 3rd, 2014 AT 8:11 PM
Tiny
JBENNETT5847
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  • 7 POSTS
I ran the engine until the thermostat dial moved and used a high-temp mercury thermometer and they were generally about the same. I'm not sure how to upload photos, but smoke came out from near the belts and several inches below the main heads seals, there was also smoke coming out of the valve at the end of the overflow tube where it connects to the vent, I have yet to check the tensioner since its too dark. I apologize for not being too good with my car information
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Wednesday, September 3rd, 2014 AT 8:24 PM
Tiny
JACOBANDNICKOLAS
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You're doing fine. Listen, the only way to properly test a thermostat is to remove it and place it in boiling water to see if it opens fully. As far as the smoke, check the water pump. Behind the pulley you should find a small round hole. It is called a weep hole. If the bearing or seal in the pump, coolant will leak from there and you will see steam.

Let me know what you find.
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Wednesday, September 3rd, 2014 AT 8:27 PM
Tiny
JBENNETT5847
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I have a mechanic coming to look at it tomorrow, I will update you on what I find
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Wednesday, September 3rd, 2014 AT 8:33 PM
Tiny
JACOBANDNICKOLAS
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Sounds good.
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Thursday, September 4th, 2014 AT 5:16 AM
Tiny
JBENNETT5847
  • MEMBER
  • 7 POSTS
The mechanic finally took a look at it, it appears the issue is somewhere in the coolant system out of the fan. Its spraying the water on the engine and the engine is cooking it and causing steam. He checked those other things and we did the method to check the thermostat and those all check out. I can take it from here with the mechanic now that I know where the issue is, thank you very much sir
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Friday, September 5th, 2014 AT 4:56 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Glad to help. Let me know how things work out for you or if you have other questions.

Joe
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Friday, September 5th, 2014 AT 8:18 PM

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