Engine Temperature Fluctuates , Roadmaster

The engine temp on my 92 Roadmaster fluctuates when I get on the interstate, around town it stays a steady 180. On the interstate the temp will go to the red zone for a couple of seconds and then go down to about 180 but for only a couple of minutes then back up to the red. It just keeps doing this, up and down, but most trips on the interstate are only about 30 minutes. should I worry? sounds like a thermostat cutting in to me but not sure about the temp being so unsteady? Need fixing?

thanks for any advice, Andie

 

Either bad temp sensor, gauge, or possibly the thermostat acting up, but if the gauge is jumping around that says electrical issue to me. Sensor or gauge would be my guess.

 

Sounds like a loose wire to sender or bad sender.
I had a bad oil pressure gauge on a Dodge do that. Hit a bump and loose oil pressure. Could be similar.

 

In addition to what has already been mentioned be sure to check your coolant level too. I don't know if your car has a pressurized overflow or if it has an actual radiator cap on the radiator. If it has a cap on the radiator itself then check the level there and not at the overflow tank. If it has a pressurized reservoir then check the level there.

 

checking

I am going to check what I can and think about having my mechanic look at it. I have a better idea now. The overflow tank is at the proper level and it does have a radiator cap. The radiator is full after removing the cap to check and the overflow tank level has never changed . I can see no loose wires but not really sure what to look for. I am inclined to keep an eye on the fluid levels and plan to check the engine once, right after I get off the interstate for a visual inspection and you can kind of smell a hot engine.

 

The thermostat is a 195 degree unit. You must have 195 for the computer to go into closed loop. The gauge sender is on the driver's side of the block between the #1 and #3 sparkplugs. The computer reference sender is on top of the intake manifold.

The senders are probably OK. The thermostat is probably your issue. They are easy to replace. Drain about a quart of coolant, and then remove the thermostat. While you have it out, clean the threads for the ground stud on the passenger's side of the housing, and the threads on the stud. The stud is the ground for your computer, and the O2 sensor.

If you want to make a nice mod, try installing the electric fans from a 93 Fleetwood. Grab the fans, upper and lower mounts, and the harness with a long pigtail from the connector back to the car. You have to make a harness, add a variable temp sensor, and get a couple of relays. I did it to my 91 OCC, and the temp is much steadier. It really cleans up the engine compartment when you remove the mechanical fan, and you free up 5 HP too.

As a side note, you can put the metal fuel lines from the same Fleetwood on your car, and get a Schrader valve port to check your fuel pressure.

 

I'd be looking at the thermostat.

 

Thanks

Sounds like it is time to change the thermostat. It sounds doable at my level of ability. I will do some research on how to do this, with some photos. I have replaced a thermostate on my old Jeepster back in the day, remember it to be pretty easy. Thanks again

 

What kind of fan does it have? If it is a clutch fan I would lean towards that.

I say this simply because around town is where you would have the major problem with the thermostat as well as distance travel. and you fan would not be turning steadily at High RPM. Where as interstate travel it would be constant higher speed. It may be worn out and "slipping" at constant High RPM?

If it has an electric fan it could also be slacking



Just thought I would toss that in there

 

Fan?

Not sure what kind of fan it has, a 1992 Roadmaster wagon. Pretty sure it is not electrical. Just looked at the engine and the fan is mechanical. The thermostat looks super easy to access, just may need to remove air cleaner. I plan to replace it as it is very low cost part and my labor is free. I will see what happens with the new thermostat and hope the problem is fixed if not go to plan B.

 

I don't think the fan clutch is the problem, as the cooling at highway speed is from air ramming through the radiator, and the fan pulls the air at a stop or at low speeds. Andilee never said it was overheating at idle. The t-stat is likely; if the impeller is rotted or slipping on the water pump shaft, that can also cause it to fluctuate, but the t-stat is easiest. Make sure when you reattach the ground wires to the stud on one of the t-stat housing bolt that the bolt's clean and the wires are not breaking or the lug's not broken.

 

idle

the car does not overheat at idle. i am going to get a thermostat today and replace it tomorrow, when the weather warms up.

 

Your statement reminds me of the time I had a t-stat go bad driving through Nevada; I replaced it the next morning in Lost Wages. I bring this up because I was so overheated myself (even though I worked in the shade just after sunrise), I stopped at 7-11 and bought a large-sized Slurpee. I get in the car, start driving up Tropicana, and got instant brain freeze on the first slurp! So I rolled down the window, stuck my head out, and slurped in a huge lungful of hot air! Brain freeze gone!

 

There's gotta be a smart remark here someplace but I am practicing self control!

 

IF a thermostat is "sticking" it will overheat at ANY time(unless it's stuck open), basically you start the car and let it idle and it WILL overheat. No if's and or butts about it. I suppose it could be fluctuating? altho that would be a first. But I could see it happening. The impeller would be the same result at idle if rotted as what I described at idle above but slipping yea I suppose at highway speed. Lets see what happens when he gets it in there