kknobl Posted February 25, 2006 Report Share Posted February 25, 2006 All, This will be kind of long, so bear with me. Lately, the temp in my Grand Prix (3.1 MPFI) has been somewhat quirky. After about the first 10 - 15 minutes of driving, temp will go up past 220 mark - usually to about 230. It never overheats and this only happens the first time I drive it each day. After about the first 10 - 15 minutes the temp will never go that high again, until I get in the car the next day and the pattern repeats itself. Under heavy acceleration, temp will slowly rise until it hits 200-220 and never goes up any further and eventually drops down to about 150 or so but overall seems to be reluctant to stabilize for any great length of time. During idle, with little air flow, temp rarely increases, but for maybe 1 or 2 degrees or so. I sat in the car for five minutes while it was idling and saw the gauge climb maybe by about 2 degrees. So, heres where I'm at - the car is my beater. I really have no performance complaints, engine has lots of life in it, still has strong (for a 3.1) acceleration. But I'm reluctant to put too much money into it. And it seems that the longer the car runs in one session, the problem manifests itself less and less frequently the longer the car is driven. Any thoughts as to what it might be? Thanks, Kevin PS - The car isn't losing any coolant. Reservoir has been at the same level for weeks now. Quote Link to comment Share on other sites More sharing options...
Guest donkeykongrape Posted February 25, 2006 Report Share Posted February 25, 2006 just a guess, but perhaps you have a lot of air in the coolant system? I've experienced problems like that before....when I opened the radiator cap, nothing but steam/hot air came out, the radiator had more air in it than coolant/water mix. Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted February 25, 2006 Report Share Posted February 25, 2006 ^^ I was gonna say the same thing about the air. Also might sound dumb but sure you have the antifreeze/water mixutre right? (50/50 or 70/30) and didnt just pour in straight antifreeze? Quote Link to comment Share on other sites More sharing options...
DiscoStudd Posted February 25, 2006 Report Share Posted February 25, 2006 I'd put money on the radiator being scaled up beyond it's limits. A brand new radiator won't set you back very much, shouldn't cost more than $150. Beware though, if you replace a scaled-up radiator, be prepared for the heater core to go out the same way... Quote Link to comment Share on other sites More sharing options...
kknobl Posted February 25, 2006 Author Report Share Posted February 25, 2006 I'd put money on the radiator being scaled up beyond it's limits. A brand new radiator won't set you back very much, shouldn't cost more than $150. Beware though, if you replace a scaled-up radiator, be prepared for the heater core to go out the same way... Thanks for all of the advice. I did burp some air out of the system and the issue of the temp rising under acceleration seems to have calmed down since burping some air out - even under hard acceleration the temp stays largely stable. However, now, the temp tends to rise when I lay off the gas and am coming to a stop. Would this be indicative of a water pump (I replaced this in the summer) and/or a scaled up radiator? Is there a way to tell if the radiator is scaled up just by looking at it or the coolant in it? And how much does a heater core for a 3.1 MPFI cost? I remember it costing about $250 parts and labor back when I had one go on my Quad4 powered Buick. Thanks, Kevin Quote Link to comment Share on other sites More sharing options...
kknobl Posted February 28, 2006 Author Report Share Posted February 28, 2006 An update... Temp problem under acceleration seems to have gone away. Temp will rise when I lay off the gas and am coming to a stop, but usually only to anywhere between 205 and 215. Hits 220 very rarely under these conditions. I ran the car tonight for a breif while until it got up to around 190 and did the touch feel method on the radiator. I didn't find any spots that were hotter or cooler than any other. Was the car hot enough, or should I use the radiator touch feel method when the temp is hotter? The car is driving me nuts - it never overheats but shows fluctuations between the 190 and 210 range fairly consistently while driving in mixed traffic. The car never overheats so it seems the cooling system is doing its job in that regard at least. Could my temp sensors be bad (read somewhere the 3.1 MPFI has two sensors)? I noticed tonight after I drove the car a bit that I parked it and the temp read 190. After shut down and key removal, gauge moved to 210. Turned key to run position without starting the car back up, and the gauge dropped back to 190. This doesn't happen all the time. Has anyone else had this, or have any idea as to what may cause that? Thanks, Kevin Quote Link to comment Share on other sites More sharing options...
GutlessSupreme Posted February 28, 2006 Report Share Posted February 28, 2006 (read somewhere the 3.1 MPFI has two sensors)? One for the ECM, one for the temp gauge in the cluster. Can't remember which is which at the moment, but one's on the rear heard on the driver's side, and the other's in the lower intake manifold, just about under the throttle body. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted February 28, 2006 Report Share Posted February 28, 2006 sensor in the lower intake by the thermo is for the ECM. the guage/light sensor is the one in the rear head. Could the thermostat be sticky? it is very easy to change on the 3.1. and removing it with the engine cold would pretty much let you see if there was an air bubble caught beneath it. Quote Link to comment Share on other sites More sharing options...
kknobl Posted February 28, 2006 Author Report Share Posted February 28, 2006 sensor in the lower intake by the thermo is for the ECM.the guage/light sensor is the one in the rear head. Could the thermostat be sticky? it is very easy to change on the 3.1. and removing it with the engine cold would pretty much let you see if there was an air bubble caught beneath it. I'm thinking that could be an issue - the temp problem didn't really manifest itself until we got a nasty cold spell. Is it possible that the cold could have anything to do with causing a thermostat to stick? I only use the car for around the town driving so it does sit in the cold all night and most of the next day... And the thing with the temp rising after shut off is very sporadic - it doesn't do it all the time... Thanks, Kevin Quote Link to comment Share on other sites More sharing options...
Crazy K Posted February 28, 2006 Report Share Posted February 28, 2006 (shrugs) if in doubt try a new thermostat. the temp guage rising would be because when the engine is shut off, the engine is still hotter than the coolant and continues to warm the coolant, which is no longer flowing... It depends how hard the engine was just pushed and how warm the enigne is for factors like that... Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted February 28, 2006 Report Share Posted February 28, 2006 I'd put my money on the T-stat sticking, along with the radiator being plugged up with crap. --Dave. Quote Link to comment Share on other sites More sharing options...
dman Posted March 1, 2006 Report Share Posted March 1, 2006 Have you tried using the two brass fitting on the top of the block to purge any air out? Quote Link to comment Share on other sites More sharing options...
kknobl Posted March 1, 2006 Author Report Share Posted March 1, 2006 Have you tried using the two brass fitting on the top of the block to purge any air out? The bleeder screws have broken off, but I did burp some air out of the system by squeezing the hoses. Kevin Quote Link to comment Share on other sites More sharing options...
Crimson Fury Z Posted March 1, 2006 Report Share Posted March 1, 2006 try a new radiator cap. my temp gauge was like that. i went to the zone and asked for a 15lb cap(what was on the radiator) and it showed only 16lb. so i changed caps and the temp is stable and i got heat again! Quote Link to comment Share on other sites More sharing options...
kknobl Posted March 26, 2006 Author Report Share Posted March 26, 2006 try a new radiator cap. my temp gauge was like that. i went to the zone and asked for a 15lb cap(what was on the radiator) and it showed only 16lb. so i changed caps and the temp is stable and i got heat again! Picked up a new radiator cap today at Pep Boys and all they had was a 16 lb cap and temp fluctuations seem to be a thing of the past - it holds pretty stead around 190-200ish. I did notice that the new cap that has "Vented" etched on it. I know on the original cap, it indicates "Closed system" - will this create any issues? Thanks, Kevin Quote Link to comment Share on other sites More sharing options...
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