Engine temperature indicator

[Yoni_d]

Hi Guys

I have a weird phenomenon with the engine temperature indicator.
Usually, when I am stuck in traffic the engine heat raises to 3/4 of the indicator (the last white line before the red)
I was a bit affraid since it also goes a bit further then that so it can be near the red line. When I parked the car, I turned the engine off but then i turned the ignition switch on without starting the car and I saw that the heat indicator is a little above the middle (below the last white line).
If I start the car - it goes above that last white line. if I turn it off and turning the ignition switch to ON then it is in the middle of the indicator...

I have been told that it seems that the engine heat is fine so there is an electrical problem somewhere...but where should I look for it? I also noticed that when I turn my lights on, the indicator jumps up a little bit.

Any suggestions?

Thanks!

[Anthony10370]

hmm, possibly a grounding issue with the sensor circuit or with the central warning unit. Check if there is any corrosion around the sensor, or on the sensor connections. The sensor is located on the water bridge. Also check the grounding on the central warning unit, there could be some power back feeding into the sensor circuit.

-Anthony,

[Yoni_d]

Can you please explain where is the location of the water bridge? so I can check the sensor.

[Landseer]

Is this new behavior, or one you just noticed, or unsure?
Its the larger-bodied of the sensors sticking out of the water pipe on the top front of the engine.

I'd think accurate measuring of the temp happens only with the car running, circulating water.

Highway or traffic, temp needle should be in almost same location.
If it runs up in traffic, then the viscous fan probably needs to be filled with special silicon fluid.
They should run below midpoint on the gauge, but they don't overheat until up in the red.
So, like most cars, there is a lot of distance for the needle to run through.
Seems lots of 928s run too hot, above mid, but people think its normal.

So, just keep an open mind about it!!!! You might, as you check sensor (which sounds ok to me ) find a way to reduce the temp of the engine.


Also, does the AC work? Does the front electric fan engage ever?

[Yoni_d]

Well, this is not a new issue. It just got a bit worse after I removed the instrument cluster.
In traffic, the temp needle is slightly below the middle. if I stop the car, it raises to the last white line and sometimes above it.
The electric fan works fine. When I use the AC the problem is a bit worse.
I checked the viscous fan and it looks fine. it is so strange. maybe I will check the engine temperature with external equipment...

Do you think the thermostat is not fully open?

[MPDano]

Originally Posted by Yoni_d

Well, this is not a new issue. It just got a bit worse after I removed the instrument cluster.
In traffic, the temp needle is slightly below the middle. if I stop the car, it raises to the last white line and sometimes above it.
The electric fan works fine. When I use the AC the problem is a bit worse.
I checked the viscous fan and it looks fine. it is so strange. maybe I will check the engine temperature with external equipment...

Do you think the thermostat is not fully open?

If you have no history on the Thermostat and Seal, this would be an inexpensive "need" anyways.

[Landseer]

You can't look at a viscous fan and tell. No way. Anybody, including the experts here and on rennlist that says you can is wrong.
The eye cannot differentiate motion changes between a fully or partially filled fan chamber.
Tried myself several times. Looked the same. But when refilled, ran the car much cooler.

The only way to tell is if you slow down and the temp goes up.

From the symptoms you described, I can just about guarantee that's your car's only issue.

Not trying to be an ass, but after dealing with 5 of them, I've got that nailed.

[MPDano]

A good way to check your Fan is to spin it cold, it should be semi loose. This allows the fan not to spin so fast, thus warming up the car. Now, get it to operating temp, not only should the fan be pushing a lot of air, but when you shut down the car and spin the fan by hand, it should feel tight.

Our Cars are pushing 30 years Old. More than likely it's time to service your Fan Clutch.

[Landseer]

Mine were significantly more resistant to hand-turning when hot, didn't cool the car properly until refilled.
I think its about slippage.

That's why, originally, the experts had me chasing all over creation for the answers. It was the fan after all.

Easy to refill, BTW.

[Yoni_d]

Originally Posted by Landseer

You can't look at a viscous fan and tell. No way. Anybody, including the experts here and on rennlist that says you can is wrong.
The eye cannot differentiate motion changes between a fully or partially filled fan chamber.
Tried myself several times. Looked the same. But when refilled, ran the car much cooler.

The only way to tell is if you slow down and the temp goes up.

From the symptoms you described, I can just about guarantee that's your car's only issue.

Not trying to be an ass, but after dealing with 5 of them, I've got that nailed.

I tried to search some sort of a manual how to make this procedure but I didnt find any. I found only one explanation about a similar fan in a different car. can you explain me how it is done? what kind of silicon oil should I use? if you have pictures, it will be great!

Thanks a lot.

By the way, yesterday I was stuck in traffic about 30 minutes without moving in 30C and although the heat indicator was slightly above the last white line, the overheating warning light turned on it was really scary. I must fix this issue!

[MPDano]

Here you go. Lots of Pics too.

Porsche 928 Forums dot com - View topic - Fan Clutch Servicing

[Landseer]

Nice write-up! Better than my old approach.

The other source for silicon fluid is the hobby radio control car market. Apparently a thick silicon fluid is used in the gearbox / diffy on those model cars.

[MPDano]

Originally Posted by Landseer

Nice write-up! Better than my old approach.

The other source for silicon fluid is the hobby radio control car market. Apparently a thick silicon fluid is used in the gearbox / diffy on those model cars.

Yup, any Hobby Store carries this stuff. I used to use this stuff in my RC Cars and Trucks. Diff Lube

TowerHobbies.com | Search Results

[Yoni_d]

This is fantastic!!! many thanks!

[Landseer]

OK

For the book worms amongst us:

[Yoni_d]

I am a book worm can you send me those images to my email? It is hard to read the text in your post...

[Landseer]

They are digital copies of what I have, so I didn't loose a generation in displaying them.

So, unfortunately, an emailed version will be the same.

Hard to read, sorry.

Hold down shift key and roll your mouse wheel to zoom (if you haven't done it, it helps on this set).

You can also copy the pictures here onto your hard drive with right click/save. Then blow them up in a photo program. Then print, piece them together and study that way. But bottom line, try filling the fan.

If you have the special set of CD's, they are located in the 150 page description document that was released to the dealers on the 78 or 79 cars, 'service info by year" docs. (You know, the cd's that the 50 year old newbie know-it-alls keep chiding each other not to buy)

Most of the docs are scanned onto the CD with more clarity.

[Yoni_d]

Thank you so much! it is readable...its just hard but possible!

[Georgian]

Yoni_d

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