PRT or leave as is? opinions requested please

[WillyHeckaslike]

That is interesting, never before heard of a black PRT being a factory fit on a 75/ZT. I've only ever known of the cream PRT being used and a quick look on ebay threw up two listings showing cream PRT's in a turbo application, the first link even being for a new system. Click ... Click

There was supposed to be strict PRT colour demarcation under Rover and while black will have been on-site for use on diesel variants on other models, such as the 200/25/ZR Click, it begs the question how did it end up on the 75/ZT?

At best maybe the PRT manufacturer could only supply in black at the time but with the cream PRT internals, at worst the wrong PRT has been used.

[chipsceola]

Originally Posted by WillyHeckaslike

That is interesting, never before heard of a black PRT being a factory fit on a 75/ZT. I've only ever known of the cream PRT being used and a quick look on ebay threw up two listings showing cream PRT's in a turbo application, the first link even being for a new system. Click ... Click

There was supposed to be strict PRT colour demarcation under Rover and while black will have been on-site for use on diesel variants on other models, such as the 200/25/ZR Click, it begs the question how did it end up on the 75/ZT?

At best maybe the PRT manufacturer could only supply in black at the time but with the cream PRT internals, at worst the wrong PRT has been used.

What can I say, that's a really good link and information. The price for new parts also appears to be very reasonable, and a viable proposition when one considers the existing hoses are all OEM and 10 years old last November.

However, unsure about reducing temperatures as car does many short trips and quick warm up must help with engine wear, economy and certainly comfort on cold days.

Am thinking now would replace right away, except only just refilled after flushing and new OAT coolant, the 3rd time since spring 2012 when HG replaced. (Now flushed refilled twice since to reduce/eliminate any contaminates remaining / also replaced metal pipe with bleed valve as original valve broken off making bleeding a bit of a chore unless using vacuum method).

Many thanks to all, advice and information is appreciated.

[steveo]

Hi all

The grey and black thermostats were introduced later ( prts fit some of the Honda range)

The black one should not be used on the K series because of the force required to move the spring to the open position ie hard spring (these thermostats dont just work on temperature they also work on load / speed)

Please also be aware that some dealers are selling 92 degrees thermostats in the wrong boxes

If you look inside the thermostats plastic housing you will see the rating stamped on the metal thermostat itself

I fitted a buff coloured one rated at 82degrees with a weak spring and the car has never run as well as it does now.

It has had no detrimental effect on fuel consumption either

Regards

Steve

[Chilljohn]

that would indicate that mg rover fitted the wrong ones to my cars then , and rimmers are selling the wrong one for the turbo then !!!! as they list the black one

[T-Cut]

Originally Posted by steveo

The black one should not be used on the K series because of the force required to move the spring to the open position ie hard spring (these thermostats dont just work on temperature they also work on load/speed)

The black type seems to operate as a conventional stat OK in mine. I haven't noticed the pressure valve opening during my relatively sedate driving style. It certainly runs 10C or so lower than the original buff one. That in itself may buffer against the loss of hydraulic pressure control, I don't know.

I fitted a buff coloured one rated at 82 degrees with a weak spring and the car has never run as well as it does now.

Curiouser and curiouser. If so, that's yet another variation. The buff ones have been rated as 87-88C historically. The complete 75/ZT range has a nominal 88C stat system of one type or another according to what I've read. I doubt my 1.8T would have run at 95-100C if the stat had been rated 82C. According to Wiki/Seloc site, the grey version is the 82C/light spring.

Wiki/Seloc: http://wiki.seloc.org/a/Pressure_Rel...ote_Thermostat

The only clear thing about it is more you read the foggier it gets.

TC

[steveo]

Hi all

I think the the biggest issue is the manufacturers of the prts

I believe Mg Rover stuck to the rules regarding colour coding but as the manufacturing rights were relaxed and other manufacturers started supplying these units the coding system fell by the wayside

Regards

Steve

[chipsceola]

Gets even harder to decide doesn't it, anyone care to explain pro's/con's of operating at 10 degree C lower temperature?

[steveo]

Hi all

Some people say it is detrimental to fuel economy but according to my dashboard i achieved the best ever 40.9 mpg recently on a run

I have noticed no difference at all in the time it takes to get the engine to temperature
I have noticed no difference in the heating (although not winter yet)

In my opinion these cars (1.8s) were designed to run too hot ,the running temperature left very little margin for error.

Remember the old saying heat causes friction causes wear

I have posted before that a mechanic i know who works for a Range Rover / Freelander dealership told me that the grey thermostat (prt) is fitted to the Freelanders as a matter of course if the cooling system is opened up for any reason.



Regards

Steve

[T-Cut]

This is my view as a scientist.
If the cooling system in it's entirety were completely reliable, then running the engine at a temperature of 100C all day would be of no consequence. The engine oil would certainly cope and may indeed perform better than in a cool running situation. The problem is, the cooling system isn't reliable. From my observations, the hoses aren't really happy at 22psi/100C. They're just too flimsy in construction IMO. And all the other leaks they get doesn't help. If you ask the engine operator professionals like truckers what temperature gives maximum performance, they'll tell you as hot as possible. Certainly 100C nominal would be considered quite normal. MGR considered normal running to go to 115C. That's not particularly hot. The standard '140' pressure cap won't vent off pressure until the coolant reaches 120C and maybe more. Some people use even higher rated caps without negative effects. I'm convinced that downrating thermostats aftermarket is to widen the mechanical tolerance to cope with today's car owners. In the main they have little idea what goes on under the bonnet and expect the car to cope with everything they throw at it with the minimum of maintenance. We live in a throw away world and cars are part of it. I'm happier running at 90C than 100C not because it protects the engine directly, but because it reduces stress on all those flabby hoses and rubber gaskets that kill engines when they fail. Most engines are wrecked through coolant loss than from high running/oil temperature.

TC

[chipsceola]

Spent several hours today, benefit of being retired, reading about the K4/16, PRT and HGF etc., there's lots of previously published information and ideas much being by respected members of various MG/Rover forums.

The engine is however intolerant to:

· low coolant level
· coolant leakage
· under cooling in traffic (loss of one or more fan speeds)
· worn / ineffective radiator cap seals (header tank)

The engine is designed to warm up quickly through the use of chosen materials and operate at temperature range of 95/105 degrees without any detrimental effect on engine oil or coolant, both of which can easily cope with that range.

Modifications to head dowels, head gaskets and cooling system with the PRT has increased reliability of the K4 over a wide range of vehicles including Land Rover, MGTF and Lotus Elise'.

There is a very wide difference in such a large range of applications, driving styles, and operating conditions perhaps highlighting the potential early HG failure.

The 88c thermostat is both correct and effective and not in itself a problem, being able to continually monitor coolant level and temperature from the driving seat, with visible and audible warnings should ensure the level never runs low, and operates within the temperature design range.

There may however be a case for lowering the OAT anti-freeze concentration from 50/50 to 35/65 or changing to standard Blue anti-freeze in an effort to prolong the life of hoses and sealants used through the engine.

In short there are many and varied reasons for early failure and modifications to prevent it, not all of which are strictly necessary to ensure reliability, pleasure and driving enjoyment.