Porsche 944 Thermostat Replacement

I am still having the issue where the temperature gauge in the 944 is working for a little bit and then pegging itself to the max after a bit of driving.  I have replaced the coolant temperature sender and a resistor in the cluster, but the problem persists.  I then started thinking that maybe the gauge isn’t bad and there is another underlying problem.  Maybe the thermostat is sticking?  Well, I don’t really think the car is overheating since it never really seems hot and the coolant is not boiling, plus the big exclamation point is not on which would indicate an overheating condition.  Either way, I decided to replace the thermostat anyway.

You will need a jack and some jack stands, as well as a catch can for the coolant.  You will need a thermostat; a 54mm standard 180 degree thermostat will work just fine.  You will also want to have some coolant, because you will have to drain it all.  Have some flathead screwdrivers of varying lengths handy, as well as some precision snap ring pliers.  This last one is important because getting that thermostat out is a little bit of a pain.

Put the car up on some jack stands, using the jack point in the center of the car to safely raise the front of the vehicle.

Undo the clamp to the lower radiator hose, the one that is connected to the radiator. 

Position your catch can underneath the hose and radiator to catch the coolant that will be spilling out.

Pull the hose away from the radiator and let the fluid drain out.

When it has completely drained out, undo the clamp that is keeping the hose connected to the water pump.  I was able to use a long flathead to get mine loose, but you may need to use other tools to take yours off.

When the clamp is nice and loose, pull the hose off the water pump and let it drop to the ground.  You can try and pull it up, but letting it fall was easier.

Lower Radiator Hose

Now the fun begins!  The thermostat is held in by a snap ring inside the water pump.  Of course it is recessed pretty deep in there as well. 

That Is The Tip Of The Thermostat

This is where those precision snap ring pliers come into play.  Use the angled snap ring pliers to close the ring and remove it from the water pump.  I found it was easier to access it from the bottom than from the top.

Thermostat Recessed In The Water Pump
The Snap Ring Pliers Need To Go In Here

You will now want to remove the thermostat, be prepared for a rush of coolant that will be coming out of the block.  Have your catch can ready! 

There are seals around the thermostat that you will need to transfer to the new one.  Make note of which order they are in.  The rubber one gets put on the outside of the thermostat, and the metal one goes on the snap ring side of the thermostat.

Rubber Seal Around Thermostat, The Metal One To The Left

Put the thermostat into the water pump, the spring side goes in first. 

Use your snap ring pliers to put the snap ring back into the water pump.  I had to use two hands to accomplish this, one to hold the snap ring closed and the other to push the ring flush against the thermostat.  You don’t want the snap ring to be crooked.

Reattach the lower radiator hose and fill the system with coolant.  Keep the vent plug open while you are filling the system to allow air to escape and to know when the system is full.  You will also want to start the car and let it warm up fully to make sure all the air is out of the system.  To do this, plug the vent, let the car warm up, and then take the vent plug out.  Cover the vent hole with something (don’t use your finger because it’s hot!) and squeeze the upper radiator hose.  This created a suction action that pulls air out of the system.  Then take the cover off the vent.  When coolant flows steady out the hole, you are done.

A small side note about the pliers:  I actually went and purchased a set to complete this job.  I had a universal set with differing attachments, which worked well for other jobs, but this one the thermostat was in the way and the mechanism that holds the attachments on were blocking me from getting a good connection to the snap ring.  After purchasing the precision set, I made quick work of the snap ring.

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