928 Cooling System check.
Thread Starter
Three Wheelin'
Joined: Jul 2016
Posts: 1,354
Likes: 102
From: Duncan, SC
928 Cooling System check.
All -
I have noticed my temp gauge going a little higher than usual lately and also noticed I have very little/no heat when the control is set that way.
I was worried I may have a flow problem or thermostat issue, etc.
in the video is just made of course everything is pretty normal (as usual) but wanted to post just in case anyone catches anything funny.
I talk through most of the video so hopefully that will tell you what you need to see - I tried to include just about anything I could think of related.
note the issue in the second video. If I let the car sit for a few minutes then restart it, then temp magically drops to where I think it ought to be all of the time…
thanks for commenting…
https://youtu.be/i9VFPJ3_-2Q
https://youtu.be/RCJJ_5wA25k
I have noticed my temp gauge going a little higher than usual lately and also noticed I have very little/no heat when the control is set that way.
I was worried I may have a flow problem or thermostat issue, etc.
in the video is just made of course everything is pretty normal (as usual) but wanted to post just in case anyone catches anything funny.
I talk through most of the video so hopefully that will tell you what you need to see - I tried to include just about anything I could think of related.
note the issue in the second video. If I let the car sit for a few minutes then restart it, then temp magically drops to where I think it ought to be all of the time…
thanks for commenting…
https://youtu.be/i9VFPJ3_-2Q
https://youtu.be/RCJJ_5wA25k
Team Owner
Joined: May 2004
Posts: 31,237
Likes: 4,221
From: Philly PA
What year is your car?
just from what I saw you might need a new rear T stat seal depends on the year.
You need a new fan clutch. they are inexpensive about 185.00.
The temp sensor connectors need D100 as does the instrument fuse.
and the grounds above the CE panel
NOTE if your gonna post videos,
please wear a smock or a shirt, or a burlap bag even,
its hard to unsee what has been seen.
just from what I saw you might need a new rear T stat seal depends on the year.
You need a new fan clutch. they are inexpensive about 185.00.
The temp sensor connectors need D100 as does the instrument fuse.
and the grounds above the CE panel
NOTE if your gonna post videos,
please wear a smock or a shirt, or a burlap bag even,
its hard to unsee what has been seen.
Last edited by Mrmerlin; Aug 5, 2023 at 10:54 PM.
Thread Starter
Three Wheelin'
Joined: Jul 2016
Posts: 1,354
Likes: 102
From: Duncan, SC
Thanks Stan
It’s an 83 US model - my understanding is that mine does not have the rear t-stat seal.
so fan clutch is susceptible even though it seems to increase in speed with engine rpm (eg not ‘slipping’ or anything)?
so fan clutch is susceptible even though it seems to increase in speed with engine rpm (eg not ‘slipping’ or anything)?
Addict
Rennlist Member
Rennlist Member
Joined: Sep 2010
Posts: 13,583
Likes: 1,046
From: Boulder Creek, CA
Ahhhh....
But did you -test- it?
Its likely old/bad.
928srus had a cheap replacement, will solve the problem.
Nordschleife Master
Joined: May 2012
Posts: 5,235
Likes: 437
From: Thousand Oaks California
I recently had a fan clutch fail on my 85. Caused it to run hot in low speed traffic until enough air got through the rad when going above 60.
Easiest way to test is to just try and spin it with the car off. It it spins easily at any point it is done. If it has even resistance all throughout, your problem lies elsewhere.
Easiest way to test is to just try and spin it with the car off. It it spins easily at any point it is done. If it has even resistance all throughout, your problem lies elsewhere.
Thread Starter
Three Wheelin'
Joined: Jul 2016
Posts: 1,354
Likes: 102
From: Duncan, SC
Updated video
Here’s a new video (belly covered this time) with the fan movement by hand after a drive to get the engine to operating temp.
Some other notes to add:
1. Engine harness was new about 10k miles ago.
2. Temp does not drop when getting up to 60 or so - once there it stays there except when I turn engine off and let it sit for aminute and then it will drop.
3. Temp today held under the top line today versus the past several days.
4. I am pretty sure it has a 185F thermostat - about 5 years/20k miles old
5. Radiator was cleaned/flushed out of car when timing belt/water pump done about 5k miles ago. Everything away very clean and seemed to flow well at that time.
thanks all…
https://youtube.com/shorts/ZJpEOaiFUL8?feature=share
Some other notes to add:
1. Engine harness was new about 10k miles ago.
2. Temp does not drop when getting up to 60 or so - once there it stays there except when I turn engine off and let it sit for aminute and then it will drop.
3. Temp today held under the top line today versus the past several days.
4. I am pretty sure it has a 185F thermostat - about 5 years/20k miles old
5. Radiator was cleaned/flushed out of car when timing belt/water pump done about 5k miles ago. Everything away very clean and seemed to flow well at that time.
thanks all…
https://youtube.com/shorts/ZJpEOaiFUL8?feature=share
Team Owner
Joined: May 2004
Posts: 31,237
Likes: 4,221
From: Philly PA
check it when its cold,
it should be difficult to spin for atleast 70 % of a revolution.
based on the first video you need a new fan clutch
NOTE you can also tell from the sound that the fan makes when you rev the engine,
it should move prodigious amounts of air and also have a sound that its working.
for a good demonstration get your box fan and listen to the fan as you run it at different speeds,
you will hear a difference as the fan is pushing more air, the car fan should do the same.
NOTE when a 928 with viscous fan starts to have cooling troubles sitting still,
the fan clutch is the first thing to replace.
it should be difficult to spin for atleast 70 % of a revolution.
based on the first video you need a new fan clutch
NOTE you can also tell from the sound that the fan makes when you rev the engine,
it should move prodigious amounts of air and also have a sound that its working.
for a good demonstration get your box fan and listen to the fan as you run it at different speeds,
you will hear a difference as the fan is pushing more air, the car fan should do the same.
NOTE when a 928 with viscous fan starts to have cooling troubles sitting still,
the fan clutch is the first thing to replace.
Last edited by Mrmerlin; Aug 6, 2023 at 03:11 PM.
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Thread Starter
Three Wheelin'
Joined: Jul 2016
Posts: 1,354
Likes: 102
From: Duncan, SC
Uodate
New viscous for cooling fan. Same result.
https://youtube.com/shorts/msMwGZy5oRs?feature=share
my understanding is that temp should drop at highway speeds. This video taken with new fan installed.
Q1: does an increase in volume of coolant leaving radiator overflow hose with increase in engine rpm indicate the water pump is moving coolant correctly?
https://youtube.com/shorts/msMwGZy5oRs?feature=share
my understanding is that temp should drop at highway speeds. This video taken with new fan installed.
Q1: does an increase in volume of coolant leaving radiator overflow hose with increase in engine rpm indicate the water pump is moving coolant correctly?
Rennlist Member
Joined: May 2002
Posts: 9,276
Likes: 1,328
From: Roswell, GA
If you haven't done this yet, pressure test the system. My 88 temps moved around. When I did my pressure test it revealed cracks in the coolant tank.
Replaced the coolant tank and gauge sits just above the first white line.
Replaced the coolant tank and gauge sits just above the first white line.
Team Owner
Joined: May 2004
Posts: 31,237
Likes: 4,221
From: Philly PA
OK lets go back here,
did you check/ remove the T stat to verify that your water bridge does not have a rear T stat seal?
NOTE They changed the WB design in late 83 so you could have the WB with a rear seal.
or someone could have put in the updated part
Is the belt tight?
Did you remove the water temp sender and clean its ground and also the connectors, use D100.
What else did you fix before this running hot happened?
Has a CE panel refresh been completed?
NOTE using the temp gauge is good for a trend ,
but actual numbers should be verified with an IR gun.
did you check/ remove the T stat to verify that your water bridge does not have a rear T stat seal?
NOTE They changed the WB design in late 83 so you could have the WB with a rear seal.
or someone could have put in the updated part
Is the belt tight?
Did you remove the water temp sender and clean its ground and also the connectors, use D100.
What else did you fix before this running hot happened?
Has a CE panel refresh been completed?
NOTE using the temp gauge is good for a trend ,
but actual numbers should be verified with an IR gun.
Addict
Rennlist Member
Rennlist Member
Joined: Sep 2010
Posts: 13,583
Likes: 1,046
From: Boulder Creek, CA
New viscous for cooling fan. Same result.
https://youtube.com/shorts/msMwGZy5oRs?feature=share
my understanding is that temp should drop at highway speeds. This video taken with new fan installed.
Q1: does an increase in volume of coolant leaving radiator overflow hose with increase in engine rpm indicate the water pump is moving coolant correctly?
https://youtube.com/shorts/msMwGZy5oRs?feature=share
my understanding is that temp should drop at highway speeds. This video taken with new fan installed.
Q1: does an increase in volume of coolant leaving radiator overflow hose with increase in engine rpm indicate the water pump is moving coolant correctly?
Temp gun when needle is up there, at the back of the Tstat, the upper rad hose, the lower rad hose.