'97 Seville Overheating

[spicynoodle256]

So, my '97 Seville has had some overheating issues in the past that I thought had been taken care of, but now the oil temp level is going up and down randomly so I'm not sure what could still be wrong. I've taken it to Firestone 3 times in the past week and they said it was fixed but now this temp gauge is all over the place. My oil has been changed, coolant has been flushed, radiator cap replaced 3 times...this last time a hose was loose and they fixed that so I'm not sure what I need to be looking for. I haven't gotten to the point where the car has overheated and display board said to idle engine, the temp gauge has just been going up and down when I've been driving. Any suggestions? Thanks!

[Cadillac Jim]

The first thing to do is to look at the OBD codes, which are your car's computer diagnostics of everything electrical in the car. Get a pencil and paper ready, and with the key on, press <OFF> and <PASS WARMER> on the A/C and watch the messages near the speedometer. Write them down and post them here.

Overheating problems often don't throw OBD codes. If there is no "smoking gun" in the list of codes, the next thing to do is to check the coolant and make sure that it's near 50-50. If it's not, the car can overheat. You say that Firestone flushed the coolant; make sure that they used "red" antifreeze when they refilled the system.

The next thing to do is to check the bypass hose. That's a small hose that goes from near the thermostat over to the overflow tank where the filler cap is. The test is, while the car is cold, to pull it off the surge tank, start the car, and see of coolant is flowing out of the hose. If it is, it's OK.

You can rule out (or determine definitively that you do have) the dreaded head gasket problem by having the coolant tested for combustion by-products. Any good radiator shop should be able to do that.

After that we can look at things like the water pump belt and tensioner (on the left front of the engine, not on the serpentine belt on the passenger side).

[barczy01]

when the car is cool pop off the radiator cap and stick your nose close to it. If you do smell a strong odor of gas your in need of head gaskets.

[Cadillac Jim]

Yes, the nose knows. If you can smell exhaust in the surge tank or anti-freeze in the tailpipe, then you have a head gasket problem. In the morning, when the car is cold, smell the coolant, then put the radiator cap back on and start the car for a few seconds, turn off the key, then walk back and smell the tailpipes. A test kit on the coolant is much more sensitive and will detect the problem long before you can smell the problem, though.

[spicynoodle256]

Thanks for the advice, I will definitely check everything in the morning, get the codes, and report back!

[spicynoodle256]

Alright here's what we've got:

IPC U1255

TCS C1221

TCS C1222

IRC B1771

RFA B2560

MMM B2149

and then after it had already said NO PCM, it said "PCM?" and stayed like that.

I smelled the coolant and didn't smell any gas and did the same with the tailpipes (which someone saw me do and laughed, by the way) and I didn't smell any exhaust/gas. I will check the bypass hose after work.

Thanks again for all the help, I really appreciate it.

[Cadillac Jim]

IPC

U1255 Class 2 Communication Malfunction (Serial Data Line Malfunction)

TCS

C1221 Left Front Wheel Speed Sensor Input Signal is 0

C1222 Right Front Wheel Speed Sensor Input Signal is 0

IRC

B1771 Cassette tape slow

RFA

B2560 RKE Message Validation Error

MMM

B2149 Right Front Mirror Vertical Position Sensor Circuit High

None of these indicates a cause for overheating. Go ahead and check the bypass hose. If it's OK, have a radiator shop check the antifreeze for being between 50% antifreeze and 70% antifreeze, with 50% preferred. While you're there, have the coolant checked for combustion by-products too.

If any of the codes are CURRENT (not HISTORY), they reflect something that needs to be fixed. HISTORY codes may be thrown by a temporary issue such as water under the hood causing a minor but detectable problem with some wiring, or they may be thrown by a bad connection that occasionally causes a problem.

The TCS codes show that your front wheel speed sensors are both disconnected or shorted. This will disable ABS, TCS, and Stabiltrak, and you will have the TC and ABS warning lights on when these errors are CURRENT.

The RFA code indicates that your fob didn't work. If that happens all the time, you might try resynchronizing your fob: press Trunk for one second, and, holding down the Trunk button, press Lock and hold for about seven seconds. If that doesn't do it, get a new battery for your fob from a hardware store, drug store, or Radio Shack and try the fob again. Then try synchronizing it again.

You can ignore the other codes, unless you want to try a cleaning cassette to fix the B1771 code. The MMM code will happen if you try to adjust one of the mirrors against the stops in any direction, particularly if you SET 1 and use fob 1 afterward. You can probably ignore it.

Most cars will throw an IPC U1255 once every several weeks or several months. That just means that a module was busy or offline when the IPC, which is the master computer for the car, is asking it for status. If it comes back quickly or is CURRENT, a module is disconnected, a fuse is out, or there is some other persistent problem with a module; in that case other codes will tell you which one. We don't see that here, so it's safe to assume for now that the U1255 isn't indicating a real problem here.

[Ranger]

Have the coolant tested for the presence of exhaust gases as suggested or borrow the block test kit from Autozone and do the test yourself if the purge line is clear.