David Kang

I am in the process of replacing my timing belt, balance shaft belt, water pump and all the front engine seals. Is the mini thermostat for the turbocharger necessary? It's part number 5 in the diagram below. I'm thinking of deleting it which will be safer to have the turbo run a bit cooler while the engine is warming up versus having the thermostat fail and circulating water to the turbo. Has anyone deleted that thermostat? Any concerns? Also, there is a vendor that sells a complete front engine seal kit with all the o rings, races, seals....? Thanks.

Gage

Go for it. I'm sure your design will be much better than what the engineers at Porsche came up with.
Reseal kits are available from 944online.

Mike Goebel

I'm guessing that Porsche put it in there for a reason.

Mike G.

dme

I've run with and without. In the winter (even here in north Texas), the car ran too cool without it. With it, in the summer, the car runs with the temp needle at about nine o'clock. Without it, it is at about eight o'clock. I put it back in this winter and will probably leave it there.

four0four

If it's any help, I am replacing one that is - at its youngest - from 2003. It failed open.

Now you just need one more data point, and we can start drawing wild conclusions

Willard Bridgham 3

The thermostat is there to protect the turbo bearings.....assume Porsche engineers know what they are doing.

Northern_aqs

To piggy back on this, the FSM and PET shows the turbo thermostat oriented with the pull side facing the front of the car, versus I’ve heard multiple sources saying it faces the engine side. Which direction is correct? My pump didn’t have one installed when I removed it to replace.

David Kang

The PET is incorrect. The thermostat can't fit as the PET shows, there is not enough clearance.

MAGK944

+1 PET is wrong on this matter and also in number of other places. Best not to rely entirely on PET diagrams as assembly guides.

GrantM

The PET may be wrong, not because the thermostat won't fit though. The thermostat will fit in either direction.

Why do we think the PET is wrong on the thermostat orientation?

What are all the other "known" PET errors? I am interested to learn about them.

Northern_aqs

Thanks for the confirmation. I had installed it as I thought it should be (counter to the FSM/PET diagram), but had doubts about trying to out-engineer Porsche.

MAGK944

The PET is wrong because the authority is the FSM and that shows it fitting the opposite way to PET.

There are too many, a couple off the top of my head are the strut “spacer” washer on early struts is shown in the wrong assembly position and the late strut top mounts are the incorrect type showing the early car ones (as mentioned). Many times they show a picture of an early part but they show several different part numbers covering later models, so they don’t shown the different later part.

GrantM

My PET and FSM (attached) show the same direction, springs forward, big part in the front, small pointy end towards the water pump.

Northern_aqs

I’d love some clarification on the orientation. My original was in pieces when I took apart the old pump.

From the PET and FSM, it would lead me to believe I’ve put mine back together wrong with the pellet towards the rear of the car.

Is the function of the thermostat to limit coolant flow to the turbo until the turbo is warm, then after shut down function as a mechanical timing valve until cool?

I.E. after running to operating temperature:

1. Thermostat is open and allows coolant to flow (via the electric pump) until the turbo cools sufficiently.
2. The thermostat closes and the lack of coolant flow shuts off the electric pump when pressure rises.

It would seem to be a simple way of timing how long the auxiliary pump is required and would address higher than typical operating temps (on track etc).

Based on this and my experience with German engineers, I suspect the PET and FSM is correct and there are a number of cars with the thermostat installed incorrectly.

Oddjob

I've always installed as shown in the 21-12a figure posted above. Had a Porsche dealer tech point that out to me 25+ years ago, saying it goes in backwards to how most people want to install it.

I did remove one on a street car one time, because I thought it might be failing (turbo water pump was running constantly, turned out to be a bad temp sensor). Car would not get up to temp in moderately cool weather, not warm enough to blow heat when wanted/needed in the cabin. So I'd recommend running the turbo therm on a street car, unless in extreme hot climate conditions.

I have run without one on my track car, because I'm always racing in warm weather and running the car hard, so no worry about the car not warming up.