Faulty/wrong thermostat or faulty temp. gauge?
#1
Track Day
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Faulty/wrong thermostat or faulty temp. gauge?
Hi guys
I changed my thermostat in my '87 944S and it's been running a bit too hot ever since. Nothing too bad, it just warms until the needle goes just above the last white line before the red starts. The fan will turn on quite often and if it's a hot day it will run almost continuously, but it's not to a degree where it is a red flag. I've spoken to Porsche about it and they reassured me that I got the right thermostat, which leaves the question: Is there a way to check whether the problem is with the thermostat or whether it is a wrong measurement causing it to display slightly warmer temps and turn the fan on more often due to it?
Or is there simply a common mistake here where the thermostat can be mounted slightly wrong, causing it to run slightly hotter?
Hope you guys can help.
I changed my thermostat in my '87 944S and it's been running a bit too hot ever since. Nothing too bad, it just warms until the needle goes just above the last white line before the red starts. The fan will turn on quite often and if it's a hot day it will run almost continuously, but it's not to a degree where it is a red flag. I've spoken to Porsche about it and they reassured me that I got the right thermostat, which leaves the question: Is there a way to check whether the problem is with the thermostat or whether it is a wrong measurement causing it to display slightly warmer temps and turn the fan on more often due to it?
Or is there simply a common mistake here where the thermostat can be mounted slightly wrong, causing it to run slightly hotter?
Hope you guys can help.
#2
Racer
If the fan is on then the thermostat is open. The fan turns on based on coolant temperature in the radiator.
There is a different set of seals and spacer washer for the thermostat depending on what water pump version you have. If the wrong ones are installed the bypass circulation path (through the head) is not blocked off when the tstat opens. This will cause higher temperature readings on the gauge because that is where the temp sender unit is.
There is a temperature rating stamped on the thermostat. What was the old one compared to the new one?
There is a different set of seals and spacer washer for the thermostat depending on what water pump version you have. If the wrong ones are installed the bypass circulation path (through the head) is not blocked off when the tstat opens. This will cause higher temperature readings on the gauge because that is where the temp sender unit is.
There is a temperature rating stamped on the thermostat. What was the old one compared to the new one?
#3
Drifting
Did you bleed the cooling system properly? After opening my system one time, mine ran hotter until I bled again--this time for a loooong time. Went back to normal after
#4
Track Day
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If the fan is on then the thermostat is open. The fan turns on based on coolant temperature in the radiator.
There is a different set of seals and spacer washer for the thermostat depending on what water pump version you have. If the wrong ones are installed the bypass circulation path (through the head) is not blocked off when the tstat opens. This will cause higher temperature readings on the gauge because that is where the temp sender unit is.
There is a temperature rating stamped on the thermostat. What was the old one compared to the new one?
There is a different set of seals and spacer washer for the thermostat depending on what water pump version you have. If the wrong ones are installed the bypass circulation path (through the head) is not blocked off when the tstat opens. This will cause higher temperature readings on the gauge because that is where the temp sender unit is.
There is a temperature rating stamped on the thermostat. What was the old one compared to the new one?
I don't know the previous or new type thermostats as I didn't change them and I don't have the old one anymore. Product ID from the invoice on the new is 25-1439.80, so it's probably 80 degrees.
#5
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I've bled it numerous times after the installation, but no air seems to come out. Also, if there was air in the system wouldn't the temp gauge fluctuate or jump whenever the air bubbles reach the temp sensor? Temp gauge is rock steady, just a tad too high.
#6
Drifting
When I had an inadequately bled system, my gauge didn't behave erratically: it was just as you describe yours, albiet never passing the 3/4 line.
Other than bleeding well, I will say that when I did my water pump, I found the thermostat info online (I believe Clark's) to be wrong in regards to fitment. I went with what seemed obvious to me instead and have no problems thermostat-wise. Unfortunately, I didn't take detailed notes, but iirc it was the opposite of what the guide said (for the shim)
Other than bleeding well, I will say that when I did my water pump, I found the thermostat info online (I believe Clark's) to be wrong in regards to fitment. I went with what seemed obvious to me instead and have no problems thermostat-wise. Unfortunately, I didn't take detailed notes, but iirc it was the opposite of what the guide said (for the shim)
#7
Racer
Ok, so if this is the case, the thermostat is actually doing it's job, but the temp reading is simply wrong?
I don't know the previous or new type thermostats as I didn't change them and I don't have the old one anymore. Product ID from the invoice on the new is 25-1439.80, so it's probably 80 degrees.
I don't know the previous or new type thermostats as I didn't change them and I don't have the old one anymore. Product ID from the invoice on the new is 25-1439.80, so it's probably 80 degrees.
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#8
Racer
Other than bleeding well, I will say that when I did my water pump, I found the thermostat info online (I believe Clark's) to be wrong in regards to fitment. I went with what seemed obvious to me instead and have no problems thermostat-wise. Unfortunately, I didn't take detailed notes, but iirc it was the opposite of what the guide said (for the shim)
#9
Drifting
That's it! Now I remember. The online procedure left me with a loose thermostat, so I used the opposite spacer and it fit nice and tight; I remember having to gently tap it together with a punch.
#10
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Great! I'll try to see if I can bleed it some more, and otherwise i'll try to space the thermostat and see if I can get it to work. Thank you so much guys!