Stuck Thermostat? 2004 1.8 MK2

Bobward · 20th March 2021, 17:59

While driving today I noticed the temp gauge had dropped to the 7 position. While stationary in traffic it rises back to 9. I got home and did some checks.
Plenty of coolant, the heaters are warm, all hoses are hot, the fan isn't on. I tried the onboard OBD and let her tickover to 94 degrees, then took her for a 3 mile drive and temp dropped quickly to 68. I had a similar issue with my diesel 75 last year and an inline thermostat sorted that right out, so I'm probably answering my own question here but 68 degrees seems much too low and I thought I'd check in with you knowledgeable chaps before I start ordering parts.

SD1too · 20th March 2021, 21:05

I agree Bob, it does sound like a faulty thermostat. Is it a PRT?

Simon

Bobward · 20th March 2021, 21:28

Quote:

Originally Posted by SD1too

I agree Bob, it does sound like a faulty thermostat. Is it a PRT?

Simon

It is indeed a PRT.

SD1too · 21st March 2021, 06:55

Quote:

Originally Posted by Bobward

It is indeed a PRT.

Thanks. Being a V6 owner I'm not familiar with those but there's plenty to read about to help you choose the replacement. Member T-Cut has researched the subject thoroughly.

Simon

TourerSteve · 21st March 2021, 07:32

Quote:

Originally Posted by Bobward

While driving today I noticed the temp gauge had dropped to the 7 position. While stationary in traffic it rises back to 9. I got home and did some checks.
Plenty of coolant, the heaters are warm, all hoses are hot, the fan isn't on. I tried the onboard OBD and let her tickover to 94 degrees, then took her for a 3 mile drive and temp dropped quickly to 68. I had a similar issue with my diesel 75 last year and an inline thermostat sorted that right out, so I'm probably answering my own question here but 68 degrees seems much too low and I thought I'd check in with you knowledgeable chaps before I start ordering parts.

Bob

We have had success with the PRT Thermostat PEL500110 which seems to operate well in the 1.8 N/A and 1.8 Turbo .

Follow this link you will find 7 different listed PRT’s under the same part number !
https://www.brit-car.co.uk/search.ph...t=&xPerPage=10

These are meant to be the same PRT model but not all will will perform the same
It seems the quality of PRT’s have become very fragmented and members fitting them recently seemingly can have other issues

I would only buy the genuine article off that list , more expensive but proven to operate correctly ,
Usually off Rimmer bros
My aim of the post is to enlighten you to that fact . The right parts are out there , but also so are a lot of pattern parts that don’t always hit the mark !

T-Cut · 21st March 2021, 08:37

Hello Bob, decisions, decisions. As Steve says, there are PRTs and there are PRTs, so how to tell what type you need - and which of those is reliabe? Perhaps the most informative source of info on the topic is here: https://wiki.seloc.org/a/Pressure_Re...ote_Thermostat

While the stat they advocate has changed a bit over the years, it does contain the basic information about the different 'types'. The type refers to the stat's temperature and relief pressure ratings. These were originally indicated by the colour of the plastic housing (buff, grey or black). Nowadays, that means very little in the general confusion created by aftermarket imports. And this confusion thickens, because Rimmer currently list different part numbers for the PRTs in the N/A (PEM100990) and Turbo versions (PEM101021) and these are different from Steve's recommendation. Historically, Rimmer's part numbers have wandered around as well. So, your best bet is to follow the advice from a satisfied customer and Steve seems to fit the bill.
Hope this wasn't too confusing!

TC

Bobward · 21st March 2021, 11:50

Quote:

Originally Posted by TourerSteve

Bob

We have had success with the PRT Thermostat PEL500110 which seems to operate well in the 1.8 N/A and 1.8 Turbo .

Follow this link you will find 7 different listed PRT’s under the same part number !
https://www.brit-car.co.uk/search.ph...t=&xPerPage=10

These are meant to be the same PRT model but not all will will perform the same
It seems the quality of PRT’s have become very fragmented and members fitting them recently seemingly can have other issues

I would only buy the genuine article off that list , more expensive but proven to operate correctly ,
Usually off Rimmer bros
My aim of the post is to enlighten you to that fact . The right parts are out there , but also so are a lot of pattern parts that don’t always hit the mark !

The small bit of wisdom I possess tells me to follow your advice. So I shall.

TourerSteve · 21st March 2021, 12:10

Quote:

Originally Posted by Bobward

The small bit of wisdom I possess tells me to follow your advice. So I shall.

https://rimmerbros.com/Item--i-PEL500110

That's the the link to the Correct thermostat at Rimmer Bros

This thermostat is one favoured by the MG boys with the TF etc
I believe now that it will be one of the few PRT's left that has a manufacturer's support as a Genuine item . (for what its worth as even the Landrovers fitted to will be getting long in the tooth but locally a few members are running this PRT in their 1.8s

Bobward · 21st March 2021, 14:04

Quote:

Originally Posted by TourerSteve

https://rimmerbros.com/Item--i-PEL500110

That's the the link to the Correct thermostat at Rimmer Bros

This thermostat is one favoured by the MG boys with the TF etc
I believe now that it will be one of the few PRT's left that has a manufacturer's support as a Genuine item . (for what its worth as even the Landrovers fitted to will be getting long in the tooth but locally a few members are running this PRT in their 1.8s

Thanks Steve. Much appreciated.

Is there anything I should be aware of when fitting? It looks a fairly straight forward job.

T-Cut · 21st March 2021, 18:46

Quote:

Originally Posted by Bobward

Is there anything I should be aware of when fitting? It looks a fairly straight forward job.

Yes it should be simple and straight forward. Having said that, I've seen at least one PRT fitted the wrong way round. While the natural positioning of the hoses makes errors rather difficult, it seems possible in some circumstances. Just to be sure, here's the way the flows go.

Equally important of course is refilling and bleeding the system. While there is a text book method, I find simply refilling and then starting the engine gets any trapped air out almost straight away. A short brisk drive and top up usually gives trouble free results. If you have a Haynes manual (recommended) the MGR method is described in detail. Alternatively, do a keyword search here for the same info. It's recommended that the air vent valve in the inlet manifold is confirmed clear by blowing down the head bleed hose. That's the small hose on the header tank filler neck. When filling up the header, you may/should see air bubbles entering the filler neck as the head is filled/purged.

TC

20th March 2021, 17:59	#1
Bobward Newbie Mk2 Rover 75 Saloon / Mk1 Rover 75 Saloon Join Date: Dec 2020 Location: Armagh Posts: 28 Thanks: 12 Thanked 15 Times in 4 Posts	Stuck Thermostat? 2004 1.8 MK2 While driving today I noticed the temp gauge had dropped to the 7 position. While stationary in traffic it rises back to 9. I got home and did some checks. Plenty of coolant, the heaters are warm, all hoses are hot, the fan isn't on. I tried the onboard OBD and let her tickover to 94 degrees, then took her for a 3 mile drive and temp dropped quickly to 68. I had a similar issue with my diesel 75 last year and an inline thermostat sorted that right out, so I'm probably answering my own question here but 68 degrees seems much too low and I thought I'd check in with you knowledgeable chaps before I start ordering parts. Last edited by Bobward; 20th March 2021 at 18:03..

20th March 2021, 21:05	#2
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,394 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	I agree Bob, it does sound like a faulty thermostat. Is it a PRT? Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

21st March 2021, 08:37	#6
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	Hello Bob, decisions, decisions. As Steve says, there are PRTs and there are PRTs, so how to tell what type you need - and which of those is reliabe? Perhaps the most informative source of info on the topic is here: https://wiki.seloc.org/a/Pressure_Re...ote_Thermostat While the stat they advocate has changed a bit over the years, it does contain the basic information about the different 'types'. The type refers to the stat's temperature and relief pressure ratings. These were originally indicated by the colour of the plastic housing (buff, grey or black). Nowadays, that means very little in the general confusion created by aftermarket imports. And this confusion thickens, because Rimmer currently list different part numbers for the PRTs in the N/A (PEM100990) and Turbo versions (PEM101021) and these are different from Steve's recommendation. Historically, Rimmer's part numbers have wandered around as well. So, your best bet is to follow the advice from a satisfied customer and Steve seems to fit the bill. Hope this wasn't too confusing! TC