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Join Date: Oct 2001
Location: The Netherlands
Posts: 580
Turbo-thermoswitch broke?

Hi,

I was reading through Clark's garage (http://www.clarks-garage.com) and saw a question about a very hot intake manifold after driving a while. I have the same problem: my intake manifold seems to be very hot after a normal drive. You can still touch it for a few secs, but then you will have to take your hand of because it's just so damn hot.

Diagnosis (quote from the page): "Sounds like you damaged the thermo switch for the pump. It is mounted into the turbo water pipe, look for a single wire connector with a black Bakelite covering. If you disconnect this switch and the turbo water pump does not immediately start when you turn on the ignition (without starting the engine), then that is your culprit."

I know exactly what part is meant, and i did disconnect the connector and then switched ignition on. Nothing, re-attached it, nothing. I tested the relay (number 7 i think): ok... I can't really test the big relay (G22?), so i'm not sure about that.
The thing is, the pump DOES run after shutdown for 30 secs, so that's good. But i have no clue if it comes on during driving... It should be, because i really want my turbo to live longer than a couple of days

Any ideas, any more tests to perform.. And HOW does the system work. What does the thermoswitch do exactly?

Thanks!

Old 01-14-2003, 03:59 AM
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The intake does get quite hot. Don't forget it is made of aluminum and conducts heat from the engine block quite well. Few metals conduct heat better than aluminum. I cannot touch mine after driving the car. I think this is normal. In fact, I use mine to dry off sweaty clothes at DE events. It also picks up heat from the turbo because of hot air rising.

My turbo water pump will run at times when the engine is running. Mine will cycle several times after I shut the engine off if the engine is hot enough. Sometimes it will just do one cycle after I shut it off; just depends. But it always does at least one cycle. My thermo switch is not stock. It came with the larger turbo. But it does the same thing.

I think the turbo thermo switch just provides a ground for the pump to come on. If the water jacket in the turbo is high enough, the switch is closed. This implies that the turbo pump should always be hot (+12v) with the ignition off. You should be able to check that. It should also be at (+12v) with ignition on-engine running. I only assume the latter because I have noticed mine come on with engine idling after a drive. The relay provides a ground for 30 seconds. Then the thermoswitch takes over providing a ground if needed from that point on.


I surmise this is how it works. I don't have an electrical diagram.
Old 01-14-2003, 04:48 AM
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Yeah, i know that it's alu and that it's a good conductor, especially with all the heat coming off the turbo that's just underneath it. Still, i wonder what is meant by 'hot' in the quote from Clarks garage? I mean, i thought the manifold was extremly hot, but then you tell me you have the same thing and it's kinda supposed to be that temprature.

Fact is: my turbo pump isn't switching on when i disconnect the singlepin connector from the thermostat. Meaning that something is wrong, or does this test only apply to models before 1988?

I'll take a picture right away, so you might clear some things up. An image often tells you more than a thousand words...
Old 01-14-2003, 04:57 AM
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If i connect the 'Thermoswitch' and switch on ignition, nothing happens. Should there be??

And: what is the 'Connector??' does this have something to do with the turbopump, it seems to go there from the fusebox...



BTW: don't mind the dirt/trash, it's been a long time since i cleaned under there..
Old 01-14-2003, 05:29 AM
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All the switch does is connect to ground. Therefore just disconnecting it won't do anything. But if you ground it where you disconnect it, the pump should run - I think. Mine is an '86. Ground the wire after you pull it off.

What else could it possibly do? It's a single wire that goes to the engine....

I could check mine tonight if this does not get cleared up today. I'm wondering about a misprint in the Clark manual.
Old 01-14-2003, 05:34 AM
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I just had some email contact with Clark, he told me that some parts of the 951 FAQ's weren't updated for a long time, because he took over the FAQ and never had the time to check the for incomplete/wrong diagnosis. We concluded that everything my car was showing me, and how it ran was pretty much ok. So, for now, i might have been just looking for problems that aren't there, but some clearification on this topic would be nice!
Old 01-14-2003, 06:27 AM
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My car is on the lift at the moment. But here is what I did. With the ignition off, I removed the wire from the thermoswitch on the turbo. When I short it to the block, the pump comes on for the 30 second interval that it runs for when you shut off the engine. This tells me that everything runs off the relay. The pump has two wires going to it. One is brown. Brown is ground with these cars. I pulled the plug apart. One pin is ground all the time. The other pin energizes to 12v when you short out the thermoswitch.

So it is not always +12v as I surmised before. The thermoswitch triggers the relay to supply +12v to pump. Ground is always there.
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Old 01-14-2003, 02:46 PM
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Thats exactly what mine did. While replacing my turbo this weekend I broke the "temperature switch."

It will only stay on for 30 seconds once grounded, then released. It I was able to pull the relay to get it to stop. I just replaced the switch last night, hopefully yours is not broken. It was a $40 part, but at least it was easy to change!

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Old 01-14-2003, 03:29 PM
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