Which Water pump. 968 on a 951

[mfloren]

I have a fairly new water pump on a 968 engine (less then 10 miles on pump, 35k on engine) that is juszt sitting around.

My 944 Turbo, its experienceing a large variance in the temperature as i drive. i origionaly thought it was a head gasket but the tests say no. Im planning on replacing the waterpump radiator (with a larger unit), and the temp sensor.

my question to the board.

I have read in other places that the 968 pump is a "upgrade" for he 944 turbo, but have yet to confirm it. my turbo is not currently water cooled so I could switch with a water pump that does not have the extra passage.

Does the 968 pump fit the 87 951 block? id rather not rip apart this engine to only find out that it does not fit.

mike

[bscpanther]

I'm not familiar with the 968 waterpump but for what it's worth, I checked out some pictures online and it looks very similar if not identical to the 951 waterpump. I'm sure there are some people here who can tell you for sure though.

[mfloren]

Thanks. and if not then ill let everyone know if i decide to do that.

I removed the thermostat last night. and should find out here shourtly if it was that.

[nize]

not sure on the pump swap, but i'm willing to bet that your thermostat is/was going bad. you can test the old one by boiling it in water.

also, running a turbo without water cooling on a street car is just asking for failure. street car turbos need the water cooling.

[mfloren]

Yes that is known. water cooled turbos depend on the water supply and not the oil to cool them.

I recently up graded the turbo to a oil only turbo so im not worried.

oh .. I have to update the fs page on the info for the turbo.

mike

I just put everything back together. ill let you know tonight what i find.

[nize]

actually, all turbochargers should have water cooling. the so-called 'oil only' turbos are not designed for street use. the primary reason race cars use oil-only turbos is to simplify plumbing, as they don't have to run a water line to the turbo anymore. on a street car, this will lead to an early turbo failure. there is no such thing as a street 'oil only turbo' and it's surprising how many people don't realize this;

from;
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html

Following a hot shutdown of a turbocharger, heat soak begins. This means that the heat in the head, exhaust manifold, and turbine housing finds it way to the turbo’s center housing, raising its temperature. These extreme temperatures in the center housing can result in oil coking.

To minimize the effects of heat soak-back, water-cooled center housings were introduced. These use coolant from the engine to act as a heat sink after engine shutdown, preventing the oil from coking...

...Many Garrett turbos are water-cooled for enhanced durability.

[87944turbo]

actually, all turbochargers should have water cooling. the so-called 'oil only' turbos are not designed for street use.

Nize, do you know if turbos on the air-cooled 911s have a shorter life than those on 951s? Just curious, haven't researched it myself.

[nize]

Originally Posted by 87944turbo

Nize, do you know if turbos on the air-cooled 911s have a shorter life than those on 951s? Just curious, haven't researched it myself.

i'm not certain, but i am willing to bet that the oil-cooled-only turbos on the older 911's feature either a turbo timer, or some sort of automatic oil pump that circulates oil to cool the turbo when the motor has been shut down hot.

this would be similar to the automatic (water) turbo pump feature on the 951.

[AaronM]

Originally Posted by nize

i'm not certain, but i am willing to bet that the oil-cooled-only turbos on the older 911's feature either a turbo timer, or some sort of automatic oil pump that circulates oil to cool the turbo when the motor has been shut down hot.

this would be similar to the automatic (water) turbo pump feature on the 951.

Neither. They depended on the driver to idle the car for 30 seconds to a minute before shutting the engine off. There were numerous "early" turbo failures and that's where the idea that turbos were only good for 100,000 miles at most came from. The 944's water-cooled turbo was fairly revolutionary in its day, especially in the circulation pump. Even my much newer and more sophisticated setup in my S70 T5 doesn't have an auxiliary turbo water pump even though the turbo is water cooled.