I purchased a 99 seville, which I had posted problems with on here before and received great responses. Thanks in advance. My question is, if the radiator pressure is between 17-19 lbs, what would that mean? Could it be a plugged heater core , bad thermostat, or something else? Says the car will slowly build up the temperature when driving? Before I took it to the mechanic, we burped the system because it seemed as though there was pressure building up, after allowing to do this, the heat started working and the temperature gauge stayed in the middle at idle. After allowing it to sit for 4 hours, then the the heat would not work, blow cold air only. Mechanic flushed, and filled, changed thermostat and water pump.

 

Well what is the specification for the coolant system pressure?

A heater control valve can be faulty but I am not sure what postion it takes when the part has failed. Unless it is like a thermostat which can be stuck closedor open. Heater core, maybe, but if you burp it and you get heat. I would rule it out for now.

Does this still do it after your coolant system service? The pressure building up makes me think that maybe a headgasket is bad and pushing the gases into the system. Did the tech mention anything about what the coolant smelled like at all? Smell your exhaust. Check your oil also.

Post more for this.

 

Hey guys, sorry if this is a little off but on my 99 STS my radiator cracked about year back (everything good now) but as i was driving home and it first happened i didnt know, the first light came on coolant temp low..nextthe temperature gauge was halfway bewteen normal and H....Looked like fuel gauge at 3/4 tank maybe little more. i put the heat on..cold...so i knew there was not coolant left in system.

My question is what more did it take for me to activate "limp home mode" did the guage have to be maxed onto "Hot" all the way. Seville guage doesnt show temp # so i dont know what engine temp was

 

The computer could have sensedthe presettemperatureat which it will try n keep the engine cool as possible. Which is done by feeding more fuel to the engine.

My other thought is that since there is a very low amount of coolant/antifreeze in the system (just reads thetemp from hot air in the system & heat transfer through each component), the engine went into limp mode because of other parts getting extremely warm.

I think you need a overhaul of your coolant system - check sensors or just replace, replace hoses if needed, check radiator & whatever else there might be to check. Get a flush also if possible after things are fixed. Coolant level that is just low enough will cause your gauge to fluxuate. This happensbecause of the flow going over the sensor then the flow not going over it on the next "wave".

 

The engine did need new head gaskets. Had the mechanic change them, and picked up the car last week. Everything was running fine, but I now notice that in the morning I leave the car warm up for 10-15 minutes which with no problem, but after driving 10 miles the gauge will slowly go over to 3/4 mark, and then hold for a minute, and then return to normal at the 1/2 way mark and be fine the rest of the day? Any suggestions?

 

Still has air in the system. Needs to be burped again. Have you confirmed the purge hose to the coolant holding tank is not plugged up? Has it been removed and visually checked for restriction?

 

I have a 2001 DeVille Northstar with a recentoverheating problem in cold weather (now below 10 F). The car had its water pump replaced a month ago due to a "coolant low" alert and drove OK for a while. Last week the coolant low alert came on again followed by engine overheating which made me take it in again (limped it in with three bars over the limit). They said the seals were a bit leaky and they replaced them, the thermostat and checked pressure OK, refilled completely with antifreeze.

Yesterday it started all over again and again I took it intothe shop bringing worries of "head gasket". Since a gallon of antifreeze was added the coolant should be all over the driveway but was not, just a few drips, and symptoms included no heat at all in the car. I have not checked the look of the oil but did smell antifreeze in the passenger compartment. The garage is experienced but may not know the subtleties of this engine. Any other ideas to look into before tearing the car apart and replacing the head gasket?

 

Should have been a new thread, not high jacked! I think you've answered your own question. Smelling coolant in the car points to a leaking heater core. Check the r/ front carpet for being wet and report back. Any good radiator shop can detect the presence of coolant in the exhaust and/or hydrocarbons in the coolant to rule out a head gasket issue.

 

car with overheating issues?

Please read:

https://www.cadillacforum.com/m_7193/tm.htm




.

 

Thanks for the advice. The car has been in the shop for three weeks without being worked on due to cold weather and a large number of overheating andother weatherfailures around here that have clogged his shop. The experienced mechanic has not seen water on the carpet but is reporting leaking still occurring from an area he just patched up. This would be the area near the thermostat and associated plumbing. He still cannot work on it but is reporting he will report back to me next week. So far he has replaced thewater pump, thermostat and resealed several leaks in two visits and he thinks it might be a rubber pipe where he cannot easily see. The water loss is dramatic (running the engine for one day loses a gallon of antifreeze) but presurization has not revealed a leak and is not apparent underneath the car. Head gasket is still a possibility. Will review Stealth's response as well.