1.8T running cool.

Stewbacca · 4th November 2016, 10:27

Morning gents

I’m hoping one of you more technically minded chaps can clear something up for me. Yesterday I topped up my 1.8T coolant by about half a cup. Later that evening I had to travel a 30 mile round trip, mostly dual carriageway so as is my habit I used to the OBD to monitor the water temperature. The water temp didn’t get above 65 deg C all journey. Even sat stationary it maxed out at a little over 70. Even given that it was a chilly night it would normally sit around 92-95. I have done some reading and have only managed to confuse myself.

Can someone please confirm if this cool running is likely due to an airlock due to simply topping up or a failed PRT? I always thought an airlock would lead to running hot?

Many thanks in advance.

TomRS · 4th November 2016, 10:40

I'd have this down to a failed PRT, if everything has been fine up until lately its probably that.
Check both radiator hoses, if they are equally warm when the car is at 1/4 temp then its more than likely a failed stat.
If the top one is hot and the bottom cold then its something else.

But in an effort to not confuse you i'd stick with it being the PRT as thats the most likely cause.

SD1too · 4th November 2016, 10:51

Quote:

Originally Posted by TomRS

If the top one is hot and the bottom cold then its something else.

A thermostat stuck shut in fact!

Tom; odd though it may sound, the bottom radiator hose will never be cold in a correctly operating cooling system. In fact, it will feel almost the same temperature as the top hose.

Simon

Stewbacca · 4th November 2016, 11:20

Many thanks for the speedy responses.

Given that I'm now going to have to order a new PRT will running around for a few days with the failed PRT do any damage?

Thanks

T-Cut · 4th November 2016, 16:59

Quote:

Originally Posted by Stewbacca

- - - will running around for a few days with the failed PRT do any damage?

No, providing the running temperature remains on the low side of normal, but -

Quote:

Yesterday I topped up my 1.8T coolant by about half a cup.

I'd be more concerned about this. How often does it need half a cupful? Coolant loss is the number one killer of these engines.

TC

EDIT: When you replace the PRT, would you report on what you find with the old one? I'll be slightly surprised to see it 'failed open', so a few photos would be interesting too.

Stewbacca · 14th November 2016, 13:16

Finally replaced the PRT.

As requested a photo of the failed one....

T-Cut · 14th November 2016, 16:08

Quote:

Originally Posted by Stewbacca

Finally replaced the PRT. As requested a photo of the failed one....

Thanks for that. It's pretty much in line with expectations. Here's a photo of another failed PRT. It shows the same sloughing off of the rubber coating on the primary valve. This one was due to oil contamination of the cooling system. Did yours look oily? I ask because mineral oil is the only thing around that will swell rubber like this. It's not an OAT effect.

EDIT:
What happens here is the main valve closes as usual, but is wedged partially open by the delaminatd rubber coating. This, and the high bypass secondary (pressure relief) valve causes the low running temperature. The actual wax piston/thermosystem remains quite functional.

TC

Stewbacca · 15th November 2016, 08:12

Curiosity got the better of me so I sectioned the failed PRT. The state of the seal was quite shocking. It didn't appear oily however the car had suffered a HGF in the past so there no doubt had been some oil coolant mixing at some point.

Closer inspection showed that the seal had distorted to such a point that it meant that the device could not close...

... hence running significantly cooler.

New PRT now fitted and all seems well.

Hope this has been of interest.

TomRS · 15th November 2016, 09:54

Very interesting too look at!

You can clearly see that its not the Wax part of the thermostat that is failing but the rubber seal.
Nice to get a failed one cut open for all to see!

T-Cut · 15th November 2016, 09:54

Very useful images. I'll put them in my little red book if that's OK.
The previous HGF is undoubtedly the source of the oil which has swelled the rubber on the PRT. It looks like it's been through a rough time.

As a matter of interest, a favour really, does the wax capsule still function? Does the valve open when you place the stat in boiling water?

TC

4th November 2016, 10:27	#1
Stewbacca Avid contributor MG ZT+ 1.8T Join Date: Mar 2011 Location: Stoke-on-Trent Posts: 139 Thanks: 4 Thanked 18 Times in 14 Posts	1.8T running cool. Morning gents I’m hoping one of you more technically minded chaps can clear something up for me. Yesterday I topped up my 1.8T coolant by about half a cup. Later that evening I had to travel a 30 mile round trip, mostly dual carriageway so as is my habit I used to the OBD to monitor the water temperature. The water temp didn’t get above 65 deg C all journey. Even sat stationary it maxed out at a little over 70. Even given that it was a chilly night it would normally sit around 92-95. I have done some reading and have only managed to confuse myself. Can someone please confirm if this cool running is likely due to an airlock due to simply topping up or a failed PRT? I always thought an airlock would lead to running hot? Many thanks in advance. Last edited by Stewbacca; 4th November 2016 at 10:55..

4th November 2016, 10:40	#2
TomRS Posted a thing or two Mk1 ZT 190 - Mk2 ZS 180 - Mercedes E63 AMG S - Ford Ranger Hawk Join Date: Mar 2016 Location: Middlesbrough Posts: 1,456 Thanks: 123 Thanked 409 Times in 281 Posts	I'd have this down to a failed PRT, if everything has been fine up until lately its probably that. Check both radiator hoses, if they are equally warm when the car is at 1/4 temp then its more than likely a failed stat. If the top one is hot and the bottom cold then its something else. But in an effort to not confuse you i'd stick with it being the PRT as thats the most likely cause. __________________ http://i66.tinypic.com/5cd6xj.jpg

14th November 2016, 13:16	#6
Stewbacca Avid contributor MG ZT+ 1.8T Join Date: Mar 2011 Location: Stoke-on-Trent Posts: 139 Thanks: 4 Thanked 18 Times in 14 Posts	Failed PRT Pic Finally replaced the PRT. As requested a photo of the failed one.... Last edited by Stewbacca; 14th November 2016 at 13:57..

15th November 2016, 08:12	#8
Stewbacca Avid contributor MG ZT+ 1.8T Join Date: Mar 2011 Location: Stoke-on-Trent Posts: 139 Thanks: 4 Thanked 18 Times in 14 Posts	Sectioned failed PRT Curiosity got the better of me so I sectioned the failed PRT. The state of the seal was quite shocking. It didn't appear oily however the car had suffered a HGF in the past so there no doubt had been some oil coolant mixing at some point. Closer inspection showed that the seal had distorted to such a point that it meant that the device could not close... ... hence running significantly cooler. New PRT now fitted and all seems well. Hope this has been of interest. Last edited by Stewbacca; 15th November 2016 at 08:49..

15th November 2016, 09:54	#9
TomRS Posted a thing or two Mk1 ZT 190 - Mk2 ZS 180 - Mercedes E63 AMG S - Ford Ranger Hawk Join Date: Mar 2016 Location: Middlesbrough Posts: 1,456 Thanks: 123 Thanked 409 Times in 281 Posts	Very interesting too look at! You can clearly see that its not the Wax part of the thermostat that is failing but the rubber seal. Nice to get a failed one cut open for all to see! __________________ http://i66.tinypic.com/5cd6xj.jpg

4th November 2016, 11:20	#4
Stewbacca Avid contributor MG ZT+ 1.8T Join Date: Mar 2011 Location: Stoke-on-Trent Posts: 139 Thanks: 4 Thanked 18 Times in 14 Posts	Many thanks for the speedy responses. Given that I'm now going to have to order a new PRT will running around for a few days with the failed PRT do any damage? Thanks

15th November 2016, 09:54	#10
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Very useful images. I'll put them in my little red book if that's OK. The previous HGF is undoubtedly the source of the oil which has swelled the rubber on the PRT. It looks like it's been through a rough time. As a matter of interest, a favour really, does the wax capsule still function? Does the valve open when you place the stat in boiling water? TC