hello all, recently my car began to severely overheat. the waterpump, coolant and hoses are all new. i figured that it was the thermostat, but not having another i just removed it all together. the problem persits, but it is not like overheating that i have ever seen it will run fine for a while the the temp will spike very quickly. by the time i notice the gauge has moved it is near or in the red. the normal range for my car is in the 7-8 o'clock range for the needle. letting the car idle seems to make things better but it does not really seem to be related to engine speed or load. it is very hot here in albuquerque but it has been for a while and this is a very recent phenomeon for my car.


i have heard that the newer than 86? have a circuit board problem that causes similar things to happen. is it possible that my 84 has a newer gauge cluster? do the 84s have a 120mph speedo? any help is greatly appreciated!!!

thanks
kyle

It just might be the temp sensor under the thermostat. Have a garage check the temp while the car is running.
Did you change the cap on the overflow tank? The wrong cap will vent too soon and allow the coolant to reach boiling temp if the system is pressurized too low.

Klaus
--
98 V70Rawd(108Kmi), 95 854T(88K mi), 75 164E(173K mi)

The clusters which have the Temp compensatin board (1986+) also have the electric speedo, so it is unlikely that you have a comp board.

Normal temp is 9:00 0'clock, below means engine is too cool and ECU, "seeing" that will add a little fuel, as if on a cold start. When I installed a thermostat in my 1988 244 after I got it, the temp moved up to normal and the fuel mileage went up, too.

Next time the temp spikes up, try this: Move the heater slide to full hot, and watch for a needle move. (In your climate, may be best to do at night.) If there is a change, that indicates that the radiator is not removing heat quickly enough.

Have you done the water blast hose cleaning? Engine off, blast from inside to outside?

There are checks for the fan clutch operation, too. But, danged if I can remember them. Someone else will chime in.

FInally it may be the radiator itself. Over time the tubes closer to the bottom get clogged, and loose cooling ability. Find a good radiator shop in ALB and see what they say about repairing yours? Some can handle the plastic end caps, some cannot. BUT - it might be better to replace the rad and avoid the fun of having the upper hose plastic nipple blow off. Makes lotsa steam! BTDT.

Good Luck,

Bob

:>)

Klaus has the key. You need to know what the real temp is. Bob is also on the ball, pointing out that the normal temp is 9:00. Your low temp could indicate a stuck open thermostat. When 'stats start to stick open, they also can stick closed. It's entirely possible that yours is sticking closed until the temp spikes up and then it opens again. A new thermostat is certainly in order here as a starter. While you're doing it, flush the rad and use new coolant.
The fan clutch is tested by letting the car sit overnight, then moving the fan by hand. It should spin freely with only slight resistance. Then drive the car until it's good and warm, then stop the engine. Again move the fan by hand. It should be very difficult to move. If it's not then the clutch is bad.
Thomas

i thought this might be the problem so i removed the thermostat all together. it still spikes...however it does not stay up like most cars when they overheat. it will fall back down within seconds if i let it idle, turn it off for 30sec, or turn on the heat. then it will run fine again for some time, then the spike again. i believe the cap is tight because it holds in quite a bit of pressure when i begin to remove it when hot. where is the temp sending unit? is it in the head? easy to replace? thanks for your replies, i really appreciate your advice and help.

kyle

is found under the intake manifold, about under the #2 rail IIRC. It has one wire to it, yellow.

There are other sensors in the neighborhood. One closer to front of the block is the knock sensor, has one brown wire. The one further back is to send engine temp signal to the ECU, it has a 2-wire harness connected.


Oh, just thought of another possibillty. That yellow wire from the temp sender unit is one of the four that have crumbling insulation. It ans the others all go through the gray connector on the firewall. If the yellow wire is grounded, the temp gauge pegs at HOT. So, maybe you are seeing the result of a yellow wire that gets grounded but not a strong connection. It is possible to run a replacement wire.

Good Luck,

Bob

:>)

There are other sensors in the neighborhood. One closer to front of the block is the knock sensor, has one brown wire. The one further back is to send engine temp signal to the ECU, it has a 2-wire harness connected.
Oh, just thought of another possibillty. That yellow wire from the temp sender unit is one of the four that have crumbling insulation. It ans the others all go through the gray connector on the firewall. If the yellow wire is grounded, the temp gauge pegs at HOT. So, maybe you are seeing the result of a yellow wire that gets grounded but not a strong connection. It is possible to run a replacement wire.

Good Luck,

Bob

There's no knock sensor on LH2.2 and earlier, right?
I think you're right about the yellow wire grounding intermittently.
Thomas