05-27-07, 06:42 PM
I just recently replaced my radiator, water pump, hoses, cooling fluid, pellets, thermostat, water pump belt, and radiator cap. I then had my car tested for exhaust gases twice by two different radiator shops. I am now driving my 97 Deville again and it seems to stay at a constant mid point for the early part of the day. If I floor it for a short period of time (5-10 seconds), I notice that about 15 seconds later, the temp gauge will go from the halfway point up to about the 3/4 point and slowly work it's way back down. On a regular day of driving, the temps under normal driving conditions will stay at the half way mark for about half the day. The second part of the day it will wander between 1/2 and 3/4 marks up and down. Is anyone else experiencing this? I have also had the system pressure tested. It passed this test also. :confused:
Do a cylinder pressure test. A coolant gas test and a cooling system pressure test may or may not detect a bad head gasket. A cylinder pressure test will for sure.
05-30-07, 02:56 AM
Thank you. Will this test aggravate the problem further? Translation- Should I wait until I am financially ready to replace the head gasket before conducting this test? Or will the car still be drivable afterwards?
The test will not hurt anything. It is simply a process of pumping up each cylinder with air and watching for bubbles in the surge tank. Before you do that, check to be sure that the purge line is clear and flows coolant.
05-31-07, 01:38 AM
Busy working today, so I didnt get a chance to do the test. However, I drove the car all day. It stayed stable at the center line until about 3:30 this afternoon. It then went to 3/4 of the way up and I turned off the A/C and turned on the heater for about 1 minute or so. The temperature came back down and stayed stable at the half way mark the rest of the day. I live in Tucson Arizona, so it's 100-103 during the day. I drove it nice and easy today without getting into it. I was amazed at how well it behaved. This is leading me to believe that it is a small leak somewhere and not the head gasket. Does this make sense to anyone?
Check the cap to be sure that it holds 15 psi. Just had a guy at caddyinfo that was having overheating problems and it was starting to look like a head gasket. Turned out his cap would not hold pressure.
06-05-07, 12:22 PM
How would you check the cap and how many psi would a 02 deville cap hold
It should hold 15 or 16 psi. It should have the pressure rating on it. You'll have to take it to a radiator shop, quick lube, repair shop, dealer, maybe AZ to have it tested.
06-10-07, 02:56 PM
Went to a cadillac dealership bought a a cap 18 psi is this right, car overheats coolant tank gets to hot
06-18-07, 10:47 AM
You should really try Ranger's advice. I'm in a similar boat myself. I can get my deville to stay running at normal operation unless I accellerate hard. Then I have to run the heater full blast to cool it back down again. I pulled the thermostat and it was toast, almost no rubber parts left. After replacement it still overheated though. I'm guessing that since it did redine temp once that was enough to misform the gasket/head. I tested the cylinders one at a time a week ago and number 4 was leaking combustion gases into the coolant on the exhaust stroke. The coolant smelled burnt. I put a little stop leaks in it to get it back to my uncles garage. I was able to make it there at normal operating temp but the gasket is most definitely the problem per the pressure test. Pulled the cradle/drivetrain this past weekend and will be performing the head gasket replacement in a week and a half. Quite an amazing design by the way!
FYI: This leak has not affected performance in any measurable way. It still has plenty of power.
07-11-07, 01:51 PM
I have been having a similar problem after replacing all hoses and radiator, water pump and thermosstat, I have NO loss of fluid however. Radiator was leaking and after many months of delay finally replaced everything. Now I can keep my 95 SLS(173Kmi) at 196F with easy driving but if I am pulling hard or going up hills it will climb to 223F, it cools back down if you go down hill etc. I can go on the highway at 70mph and maintain 196 - 199F no problem. Any thoughts?
Have a cylinder pressure test or a coolant exhaust gas test done. Sounds suspiciously like head gaskets.
we say headgaskets all the time but another related issues is a pulled headbolt due to thread failure that causes coolant to leak around the headgasket, thus we point to the HG but its really a failed headbolt but the problem is the same as a headgasket leak. I had pulled headbolts on my front bank and I drove the car for 1 solid year with no problems except a misfire after cold-soak (engine less than about 70°F) After the car warmed up to over 120° the stumble went away and I went about my business (I tried diagnosing / changing parts and then I did a coolant test, voila combustion byproducts). It can take some time to show up though because the first time I had it tested it came negative, the second 6 months later showed up positive. The cold-soak just highlighted the problem for me at least...