Bleeding the coolant
Nordschleife Master
Joined: Sep 2005
Posts: 5,107
Likes: 4
From: San Francisco
Clarks-garage.com had a great write-up. There is a drain plug on the radiator and on the block. I just use the one on the radiator since there isn't much in the block. The bleed screw is located between the fuel rail and intake boot on your car.
Instructor
Joined: Sep 2005
Posts: 157
Likes: 0
From: Dacula, GA
The thermoswitch is at the top of the radiator, so you don't need to drain much. Just drain a little out the radiator plug. If you drain just a little and don't drain the block, bleeding won't be necessary.
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Joined: Dec 2003
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From: Vestal, NY
Hey;
Have the new switch in your hand as you unscrew the old one, and immediately pop the new one in place of the old. If you are lucky and everything goes smoothly, you should not lose much coolant when swapping the switch out. Not enough to worry about. If you have a fumble and lose a bunch of juice, or just feel better being safer and bleeding it, do the following. This is what I do to bleed the cooling system in any event. This is the shortest method with the least chance for failure (incomplete bleed).
I fill the system with the bleed screw open. This allows the block to fill quickly. The tank will fill easily. Fill it till you see fluid in the tank, then go do something else for a bit. When you come back the tank will be empty, as gravity and time have done a lot of the job for you. Refill and repeat this until you see fluid start coming out of the bleed screw. Close the screw.
Take the proper precautions and start the engine and by some means raise the idle to 2-3000rpm. On early cars I tape the throttle cable to the air box lid. On Later cars or Turbos I use a piece of mechanics wire to hold the throttle open.
Open the bleed screw. There is not much to do for a while. You will see sporadic spurts of fluid, and a lot of bubbles or foam. Let it be. After a while you will see more pronounced spurts of fluid. Let it be. Still later you will see a lot of fluid with only an occasional burp of air. LET IT BE. When the screw is ready to be closed, you will know. You will see a solid strong JET of coolant blasting out of the screw, uninterupted. THEN and ONLY THEN are you close. Let it go for a few more seconds just to make sure, and you are finished!
In then end , you only lose less than a quart or so.
Have the new switch in your hand as you unscrew the old one, and immediately pop the new one in place of the old. If you are lucky and everything goes smoothly, you should not lose much coolant when swapping the switch out. Not enough to worry about. If you have a fumble and lose a bunch of juice, or just feel better being safer and bleeding it, do the following. This is what I do to bleed the cooling system in any event. This is the shortest method with the least chance for failure (incomplete bleed).
I fill the system with the bleed screw open. This allows the block to fill quickly. The tank will fill easily. Fill it till you see fluid in the tank, then go do something else for a bit. When you come back the tank will be empty, as gravity and time have done a lot of the job for you. Refill and repeat this until you see fluid start coming out of the bleed screw. Close the screw.
Take the proper precautions and start the engine and by some means raise the idle to 2-3000rpm. On early cars I tape the throttle cable to the air box lid. On Later cars or Turbos I use a piece of mechanics wire to hold the throttle open.
Open the bleed screw. There is not much to do for a while. You will see sporadic spurts of fluid, and a lot of bubbles or foam. Let it be. After a while you will see more pronounced spurts of fluid. Let it be. Still later you will see a lot of fluid with only an occasional burp of air. LET IT BE. When the screw is ready to be closed, you will know. You will see a solid strong JET of coolant blasting out of the screw, uninterupted. THEN and ONLY THEN are you close. Let it go for a few more seconds just to make sure, and you are finished!
In then end , you only lose less than a quart or so.
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Joined: Mar 2002
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From: Boulder, CO
If you are trying to change the coolant a wet vac does a good job of getting the old coolant out via a radiator hose.
For refilling, I open the bleeder screw, clean off the end of the overflow hose and stick it in my mouth. Fill the tank and then put your hand over the filler neck and blow into the hose. Do that a few times and then start closing the bleeder screw between breaths after you get squirts of coolant out of the bleeder. Run the car up to temp and bleed any traces of air out of the system and you are set. With this method it's easy to get almost all the air out before driving the car, nicer than having a hot spot in the head and easier IMO. Rise out your mouth, perhaps with beer, and you should be OK.
Do not swallow coolant, or beer contaminated with coolant.
-Joel.
For refilling, I open the bleeder screw, clean off the end of the overflow hose and stick it in my mouth. Fill the tank and then put your hand over the filler neck and blow into the hose. Do that a few times and then start closing the bleeder screw between breaths after you get squirts of coolant out of the bleeder. Run the car up to temp and bleed any traces of air out of the system and you are set. With this method it's easy to get almost all the air out before driving the car, nicer than having a hot spot in the head and easier IMO. Rise out your mouth, perhaps with beer, and you should be OK.
Do not swallow coolant, or beer contaminated with coolant.
-Joel.
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Instructor
Joined: Sep 2005
Posts: 157
Likes: 0
From: Dacula, GA
Originally Posted by WizPorsche944
But I was going to try the method discussed on here, getting the switch from the top and not draining at all.
Three Wheelin'
Joined: Aug 2007
Posts: 1,417
Likes: 0
From: Upton, Massachusetts
I have an early 944 and i was wonderin if its different for the 85.5, but i cant get to the top of the raditor. whats the best way to get to it? remove the front nose peice that hold the Porsche emblem?
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Joined: Mar 2002
Posts: 351
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From: Mass
As John said. Don't bother draining the system. The process of doing so will create more mess by trying to do it "right" than just loosening the switch, flipping out the old and quickly inserting the new. I just went through it with my S2.
Fans Running temp switch sources
Jacking up the front and removing the under tray makes it go much cleaner.
Fans Running temp switch sources
Jacking up the front and removing the under tray makes it go much cleaner.
