Musche

In an effort to keep my car running as cool as possible, would it be of any benefit to remove the small turbo thermostat so coolant always flows through the water pump and radiator? I'm not sure why it is in there in the first place. One would think you would want coolant flowing through the turbo and radiator all the time. I don't drive the car in winter or colder days so bringing these parts up to temperature is not necessary. Just a thought.

Alpine951

The water would never cool enough to cool down the engine if its not sitting in the radiator cooling down waiting for the Tsat to open. Thats is what the purpose of the tsat is for. It keeps the water in the radioator where it can cool down and then be sent to the engine to cool it down. I think the car would run very hot and overheat.

Musche

Alpine,
I understand this concept with the water pump thermostat but what about the smaller turbo thermostat? I wouldn't think this little amount of water would cause any overheating issues. That is unless if cooler water from the turbo would cause the larger thermostat not to open since it dumps back into this area in the water pump.

Alpine951

Sorry. I guess I should have read your post a bit slower. Just don't pay attention to anything I say.

John Welch

The thermostat is to keep the water IN the engine until it reaches operating temperature, at which point it opens to let the hot water cool. I can't answer the question though. On a 928, you definitely do NOT want to remove the thermostat, but this isn't a 928...

Bri Bro

The topic is about a second thermostat that is only for the turbo water cooling system. This thermostat is about the size of your thumb, the main engine thermostat is about the size of you arm.

The only purpose I see it serving is to block the flow of water to the turbo until the block is up to temperature. This would decrease the warm up time. Taking it out should not make a bit of difference in a warm weather area and for track cars it seems like a very good idea.

There was a post about making the plastic cap out of metal since the plastic one has a limited lifespan. I think it would be take a fair amount of setup time to make a metal one. I will show it to the mechanical guys tomorrow and see what they think.

Tom M'Guinn

I think I've successfully debunked this theory (on the 951 anyway). When I lived in Florida (average temp in the low 90's), I drove for over a year without a thermostat, and the car ran very cool -- cooler than with a thermostat installed. The drawback is that some amount of coolant recirculates within the pump (since the bypass plunger on the back of the thermostat is not there to block the pump's internal bypass) but overall the car ran cooler for me.

Tom M'Guinn

Brian, if you can get some made up, I'll help pay for at least a few. Seems like a perfect CNC part. I'm tired of changing the plastic ones.

KuHL 951

I always assumed the turbo thermostat also effected how long the turbo cooling pump runs after shutdown. Is the turbo timer preset for a fixed time under all conditions rather than temp?

Tom M'Guinn

If I recall, it runs for at least a fixed time after shut down, and anytime the temp exceeds a set point. Now I'm curious if the pump runs after you turn off a cold motor -- i.e., when the tiny t-stat is closed and no coolant is flowing. Also curious is its a good idea to run a colder than stock big t-stat, if doing so means the tiny t-stat might not get hot enough to open...

Bri Bro

The run time for the Turbo pump after the engine turns off is fixed. I just started my car in the garage, let it run a few seconds and shut it off. The pump ran for about 30 seconds, even with a cold engine. As I remember, the turbo pump I took apart after a replacement didn't have an impeller that contacted another surface. In a boat water pickup pump, a soft rubber impeller is pushed against a metal plate. Run it dry and the pump burns up. I bet the turbo thermostate also has a dribble hole to allow some water to flow even when the thermostat is closed. Don't have one handy to look at.

Musche

Beab,
When I had my engine apart, there was no hole in the smaller thermostat to let any small amount of water through. When this thermostat is closed, water circulates through the reservoir and back. And yes, the electric pump runs regardless of whether the thermostat is open or closed;25 to 30 seconds after the engine is shut off or longer until the temperature switch opens back up at 115 degrees. I'm just trying to see if this t-stat is really necessary. I already drilled a small hole in the larger thermostat to allow a small amount of water to flow around it. The old racers that I know did this to keep air pockets from forming around the t-stat when the system is drained and keep temperature differentials on both sides of a closed thermostat to a minimum.

phils87951

Ill venture into this one.

the Turbo aux pump will operate due to 2 parameters, 1, a timer ie: just turn the engine on and off, ± 30 seconds, it will also be triggered on by the temp sensor in the outlet pipe and will run till the temp. of the coolant comming out of the turbo is low enough to prevent damage.

When the pump is on ( I may be mistaken) but the coolant only circulated thru the expansion tank and not back to the rad.
The Small Tstat is there to prevent thermal shock in the event that the car is run hard ( ie: getting the turbo real hot) and having cold coolant flowing thru it.

If you are having temperature problems I would look more towards an "old" radiator, fins partially filled with bugs or maybe a splattered BMW against your rad..

theedge

Id probably be in for a metal Turbo Tstat housing!

Musche

Brand spankin' new radiator already in. I did find an intermittent turbo temp switch which has been ordered and will be replaced. I was just wondering about the function of the small t-stat and if is really necessary. If it can come out with no adverse effects, one less thing to go bad.