Dr Strangelove

I recently took a new-to-me 944T to the track. It was a mid eighties day and the car has a number of engine modifications. After a 25 minute session, the turbo cooling pump ran for about 45 minutes or so. Does that seem within spec?

Thanks.

-Bruce

refresh951

Should only run for about 30 seconds after shut-off.

Dougs951S

The main reason that would happen would be a sticky relay, look into that first.

Adker

The aux pump runs about 30 sec after ignition shutoff, it can be re-triggered by the turbo temp sensor on the turbo cooling loop. It will continue to re trigger the pump until the turbo temp sensor is below its set temperature. I have never seen it re-trigger for 45 minutes (yes I track the car) It has a single wire connection, just take it off and see if the issue goes away. Then replace parts until this issue goes away.

Carlsbergas

Mine runs whenever it wants, or it doesnt run completely.. lol might be temperature senor, or rellay..

Dr Strangelove

This is consistent with what I have read elsewhere (e.g., Clark's).

I'm interested in your use of the term "re trigger". When the pump is re-triggered, does this appear to you as a series of discrete cycles? I ask because my 45 minutes run time appears continuous to me.

So if I understand the gist, we are looking at the relay or the temp sensor as the likely causes?

Thanks.

Oddjob

Yes, if the temp sensor goes bad, it can cause the pump to run continuously until the battery dies - have had it happen. Can check this by seeing if the pump is running while the engine is on (if the sensor is working, the pump will not be running with the engine on. If the pump does not run w/ the engine running, then check the relay.

The little turbo thermostat could also be failed closed, which could cause the pump to run intermittently while the engine is running, but very much doubt that would cause the pump to run for extended periods of time after the engine is shut off.

Willard Bridgham 3

The pump runs until the thermostat is satisfied. If I run mine hard on a warm day, it will run for 45 min before the temp comes down.

Oddjob

Then you likely have a bad relay or temp sensor too...(?)

blown 944

There is a Cap in the relay that allows for a 30 second run time after the temp switch is activated (or deactivated)


You can change it out for a larger Cap if you'd like additional run time. There are a couple threads on the overall operation on here.

Adker

The re-trigger appears to make it run continuous until the turbo temp sensor turns off. The run time is in 30 second periods but the retrigger causes this run time to appear as a continuous run.