Pressure Relief Thermostat (PRT) - How to Replace

Later TFs had a different configuration of thermostat fitted as part of the search for the cure to HGF.

The PRT system moves the thermostat from the original position under the inlet manifold to the outlet side of the engine.

You will find it here.



You'll need these.





To access it, you will need to raise the rear of the car. I used the central jacking point to lift it and positioned axle stands under the subframe. I also chocked the front wheels. Ensuring that the car was safe and secure.



I released the rubber hose from the underfloor pipes positioning a suitable container to catch the coolant. And then opened the three bleed points - Radiator;Heater matrix; and return pipe in the engine bay.




Once all the coolant has drained you will be able to undo these three clips to free the PRT module. Be aware that there will be coolant held behind the thermostat. (Does coolant help hair growth?)probably not...

With the PRT removed I tested it in boiling water. It remained closed - rock solid.

Replacing with the new PRT module is obvious enough and then you need to refill with coolant,(You will need 10.5 litres if you've previously extracted all the coolant) - bleeding air out at the three bleed points(heater on full hot). Run the engine with the expansion cap off, topping up as necessary. Replace the cap, and keep checking for leaks.

If you're happy there are no leaks, test drive the car. Check the heater is working and the coolant level is OK on return.

Thank you for taking the time to log your problem the solution and this handy guide :thumbsup:

I can report that the heater is working properly again. :yesnod:

Also worth noting that the PRT conversion certainly makes changing the thermostat easier than the original position.

David Aiketgate wrote: I can report that the heater is working properly again. :yesnod:

Also worth noting that the PRT conversion certainly makes changing the thermostat easier than the original position.

Thank you for posting this and the "how to" :thumbsup: Is there a "how to" for fitting the PRT conversion and is it possible to fit a PRT with the stainless steel engine pipes that are being sold by B&G?? :shrug:

bryan young wrote:

David Aiketgate wrote: I can report that the heater is working properly again. :yesnod:

Also worth noting that the PRT conversion certainly makes changing the thermostat easier than the original position.

Thank you for posting this and the "how to" :thumbsup: Is there a "how to" for fitting the PRT conversion and is it possible to fit a PRT with the stainless steel engine pipes that are being sold by B&G?? :shrug:

There isn't a How to as such.

I've got two photos showing the pipework configuration before and after.



This is how the pipework connects to the underfloor pipes.



This is how the PRT fits in, with the original again to compare.



The hoses connect to the engine and metal engine pipes in the same manner otherwise. Notice how the prt reverses the flow through the radiator. Obviously you need to replace the original thermostat with a blank.

Thanks for this. How long does it take to change the PRT.

I have one to do and I'm new to the TF.

Thanks

Simon

Like for like replacement is possible to do in an hour. You probably spend more timerefilling and bleeding the system afterwards.

Simon Morriss wrote:

Thanks for this. How long does it take to change the PRT.

Changing the PRT itself doesn't take too long. An hour? But you need to drain the coolant and then refill the system and bleed it which takes a while. It depends on how you work. A professional would probably do the whole job in less than an hour but if you faf around and drink tea, like me, it will take two or more!

It can be tough to remove the hoses but if you poke a screwdriver between the hose and the PRT to get it started it helps a lot. You'll need the car up on ramps or axle stands at the back to reach it (replacement is from below).

Apologies if this is a silly question but....I've read a few article on the PRT and they all seem to be on the TF's. No reason I wont do it to my year 2000 F is there ?

Now I've finally got her running dry, new engine, some new hoses, new clamps, new radiator etc.

And then of course, do I go waterless coolant ?

Mat

I think you would be daft not to. Obviously you would have to remove the existing thermostat & replace it with a spacer (which can be the thermostat with the gizzards removed) IIRC. You wound need the plumbing, but if you’ve been reading up on it you already know & it’s relatively straightforward.
If you buy a tangle of pipe work off e-bay (other auction sites are available) do inspect the device itself, I had two where the internals had hernias, before I got a good one & that now needs changing.
This post is dangling off the end of David’s original post & that implies you have done the book work but there is one picture which I referred to & I’m buggered if I can remember where you’ll find it on the net. I’ve a copy on the workshop computer, if I remember I’ll glue it to a message tomorrow.
M

Airportable, M, thanks so much for taking the time to reply, didn't realize they can be a bit temperamental. thanks again.

Mat, a tiny bit wiser today