tempature gauge spikes up

i have been having a problem with my car. i recently replaced the intake boot since it was cracked, well to be honest it was missing a big chunk. i replace the intake boot and i ran it about 15-20 miles and i see the temperature gauge spike up to the red well i turn on the heater and made it home. well i check the coolant and it needed some so i filled it. started the car til it warmed up and since it was at normal temperature(1/2 / noon) i went for a drive first at slow speed then i went on the freeway well i was just getting on when the temperature spiked again up to 3/4 once again turned on the heater and as quick as it went up it came down to 1/2. im not sure what to do now? is it really overheating? i had it on for over 30min just parked, drove about another 20min at slow speed without a problem. PLEASE HELP!!!

Have you checked the coolant level when the engine is cold?

You may have a high instrument cluster. If so, search here for a way to unlock it so you can read actual coolant temp.

yes i filled it to the second dont and bleed it, but i still had a go up to 3/4 of the temperature gauge.

I checked the oil temp and it was 239. Ran it 60 mph and went to 237f. Then i parked and turned off and turned back on and it went up to 244f. The antifreeze runs thru the radiator. I did not see the aux fan turn on though.....???

What does this mean: "to the second dont and bleed it?"

What was the result of measuring the coolant temperature with the gauge cluster?

i ment the second dot. it seems to overheat more when its going than when its parked.... how would i check the thermostat without taking it out?

I found paper work on the car from the previous owner and it was taken to a shop and advised to replace fan clutch, aux fan switch, belts and he declined. He only replaced expansion tank, radiator & hose. so i guess i will start with the fan clutch and check out the blades

maybe impeller on the WP slipping or disintegrating... .

Ok so i replaced the fan clutch and it seemed like it fixed the overheating problem. I just have a few questions. I was watching the coolant temp with a OBD II and the temp went from 199 to 229f and always stayed right at half (noon) is this normal? While driving it went from 210 to 229f is the normal temp or is it a litte high? Where does your temp sit at?

I had to order a fan clutch as well, mine was doing the same thing. Not 100% sure about the temp variation but you are only talking 30 degrees so this may fall within the operating temp of the car so the gauge may not move.

229° F is high. That's 109°C.

You should have between 94-96°C (201-205°F). It "could" go as high as 98°C (208°F) in stop-and-go traffic, if it's a hot day and fan clutch or aux fan is going bad.

The car might not be bled properly. Your temp is too high. Hope the engine is still OK. The temps you posted are close to the v8 engines.

Originally Posted by doru

229° F is high. That's 109°C.

You should have between 94-96°C (201-205°F). It "could" go as high as 98°C (208°F) in stop-and-go traffic, if it's a hot day and fan clutch or aux fan is going bad.

The car might not be bled properly. Your temp is too high. Hope the engine is still OK. The temps you posted are close to the v8 engines.

well its 25-30 Fahrenheit here and i checked it with a obd. well it sits right a 1/2 were it has always been. any suggestions?

Originally Posted by danni19

well its 25-30 Fahrenheit here and i checked it with a obd. well it sits right a 1/2 were it has always been. any suggestions?

If your KTMP is reading high, chances are you have "unhealthy" temps.
I have no idea what has been done to the car, but everything points to the cooling system, won't you agree?
If the cooling system hasn't been changed in the last 100k miles, chances are lots of things are on the verge of failing. As I said, I have no idea what has been done or not on your car, and you didn't mention it either.
So, if someone did a cooling job before you purchased the car, you have to know when and you want to know what parts went in there. If nothing has been done (with the exception of the fan clutch), then probably another part could have failed. Or when the fan clutch bit the dust, the car overheat ever so slightly, enough to loose some coolant (as you mentioned you had to top off), meaning that there could be an air bubble, which in turn could be a real pain in the rear.
Or as someone else mentioned, your WP might not be able to do the job anymore. Or maybe the T-stat has fits.
Once you start changing 1 (one) part in the cooling system, without changing anything else - you're doomed. You will be chasing all kind of failed components one after another.

Thought you read through this and other forums about cooling systems of e39.

Originally Posted by doru

If your KTMP is reading high, chances are you have "unhealthy" temps.
I have no idea what has been done to the car, but everything points to the cooling system, won't you agree?
If the cooling system hasn't been changed in the last 100k miles, chances are lots of things are on the verge of failing. As I said, I have no idea what has been done or not on your car, and you didn't mention it either.
So, if someone did a cooling job before you purchased the car, you have to know when and you want to know what parts went in there. If nothing has been done (with the exception of the fan clutch), then probably another part could have failed. Or when the fan clutch bit the dust, the car overheat ever so slightly, enough to loose some coolant (as you mentioned you had to top off), meaning that there could be an air bubble, which in turn could be a real pain in the rear.
Or as someone else mentioned, your WP might not be able to do the job anymore. Or maybe the T-stat has fits.
Once you start changing 1 (one) part in the cooling system, without changing anything else - you're doomed. You will be chasing all kind of failed components one after another.

Thought you read through this and other forums about cooling systems of e39.

as far as i know the only things that have been replaced are the expansion tank, radiator & hose from the previous owners. now i replaced fan clutch, belts and intake boot. now im going to replace the temp switch if i recall right.... its right next to the expantion tank on the radiator. hope this works...

Originally Posted by BigCo540i

I had to order a fan clutch as well, mine was doing the same thing. Not 100% sure about the temp variation but you are only talking 30 degrees so this may fall within the operating temp of the car so the gauge may not move.

Thanks thats what ive been reading online. so where does your temp sit normally?

The gauge is buffered and therefore not accurate.

My car is a 530 but just as an example, my car is fully warmed at 106 but it will read noon when ktemp is still in the 80's all the way to 106.
Best bet is unlock the comp and use test 7 ktemp.

Originally Posted by Topaz540i

The gauge is buffered and therefore not accurate.

My car is a 530 but just as an example, my car is fully warmed at 106 but it will read noon when ktemp is still in the 80's all the way to 106.
Best bet is unlock the comp and use test 7 ktemp.

Topaz, if the 106 is degrees centigrade (Celsius), your KTMP is high. You might have a fan clutch issue or something else. Whne my original fan clutch bit the dust, I had almost the same readings. With the new fan clutch, in hot summer days it sits solid at 96 when fully warmed up, and toggles 97-98°C in stop-and-go with AC on. With AC off, it's back to a solid 96°C. Now, in winter, it sits solid at 94-95°C, and hits the 96°C mark only if it's a tad warmer and heavy stop-and-go traffic.

ok so i replace the temp sensor and bleed the coolant system. this what the temp was a now 217f (102c) to 224f (106c) with the heater off. with the heater on it was 201f (93c) to 205f (96c). does this sound better of am i still having a problem? does anyone know where the OBD II CAN reads the temp from???