Our 1.8T running temps

[T-Cut]

Originally Posted by ceedy

Just for info...
The innards of my our old PRT stat.

And my 3D rendition.



There's an animation in my head. I just have to work out how to do it!

EDIT: Note the four bypass drillings. This also influences how the coolant flows through the PRT system.

TC

[milford man]

There should only be one thermostat fitted depending on the year. Either the PRT or the one behind the engine. When you have a PRT there should be a dummy thermostat fitted behind the engine. Its a thermostat without a middle.

Regards John

[T-Cut]

Originally Posted by milford man

Hi John. There should only be one thermostat fitted depending on the year.

The discussion at present is about the effects of having a second stat fitted when there's already a PRT in place. It's obviously a complex issue.

TC

[kaiser]

The picture of the PRT stat is interesting, as it looks as if this stat is just a normal stat with a block disk at the bottom. Looking at the small spring, it is evident that this spring is not going to be moved by water pressure only. The pump pressure from water flowing in the system would be a fraction of a bar and unable to move that spring.
But that can be verified by a simple test.
It looks as if this thermostat is similar to the one used in the V6, where the disk at the bottom simply blocks re-circulation of water through the block, once the engine has heated up, as it follows the thermostat opening and simply covers a hole that allows water back into the block.

If this is the case the classic story of the PRT is a figment of someone's imagination.

Originally Posted by ceedy

Just for info...


The innards of my our old PRT stat.








C.

[T-Cut]

Originally Posted by kaiser

If this is the case the classic story of the PRT is a figment of someone's imagination.

There are a few informative sites giving the technical details of the PRT and how it works. They're worth a read for anyone unclear about why it was developed and how it works. For example:http://wiki.seloc.org/a/Pressure_Rel...ote_Thermostat

Your overview of this is, in my opinion, incorrect. The secondary valve spring is of variable tension depending on which engine the PRT was designed for. These were coded as 'light', 'medium', and 'heavy'. MGR identified the relief valve settings by putting the stats in plastic cases of three different colours. If the function of the second spring is simply to hold down the smaller bypass valve and accomodate some piston overthrow (as in the KV6 and diesel), it wouldn't require three versions. Note also the bore of the bypass loop. It's considerably larger than in the standard system because the idea is to increase volumetric flow rate through the engine by opening the relief valve at higher revs.

The differential pressure needed to open the valve is created by the pump. In my evaluation, I measured the pressure needed to lift the 'light' valve using a torsion scale calibrated in grams. The force amounted to around 2psi which was calculated from the valve disc area (the bleed holes taken into account). In this particular case (the buff coloured type) the valve opens at exactly 2,000rpm. This was fitted to my 1.8T from the new. Later, I swapped it for the black version as an experiment. At the time, Rimmer/Xpart said this was the version I needed. With the black version in place, I see no pressure relief at all. I'm clearly not revving the engine enough. Subsequent information published by the Lotus enthusiasts show this stat is unsuitable for the K-16. The currently recommended stat is the third, grey type.

Having purchased the latest grey version fom Land Rover (who couldn't tell me anything about it) I found the relief setting to be identical to the original buff one. I took this as indicative of a loss of 'identity', a fact supportedby discussions within the Lotus group, who say the colour codes are becoming mixed and confused.

Clearly, PRTs are different from the other double-valve types fitted to MGR engines. They are also used on the K-16s fitted to the Lotus Elise and the MGTF sports cars where their functionality is well understood and reported.

Unfortunately, the background understanding of the PRT is being lost now MGR has gone. PRTs are today made as pattern matched 'in-line' thermostats with indefinable spring tensions and colour codings. These are mainly through Land Rover distributers who have never heard of a PRT and have equally little information or understanding of them.

TC

[kaiser]

Referring to your drawing, the bottom disk is off the base, when the thermostat is closed, allowing flow past the bottom part and up to the engine, effectively blocking flow through the radiator.
As the thermostat opens because of temperature, the bottom part, the disk, moves to the right, and closes off the flow from the right side, allowing only flow through the radiator.

This is the exact functioning of the KV6 thermostat set-up. Recycling water in the engine block until hot, and then after a short period with both systems open, flow will only go through the radiator.

There is nothing in this diagram that will allow a pressure opening, unless when the thermostat is already open and the stop disk forced against it's seat. And then what good would that do?

[T-Cut]

All I can suggest is that you search out and read the background describing the PRT's development at MG Rover.This is a start: http://www.mgf.ultimatemg.com/group2...ifications.htm

TC

[picky747]

My 1.8t was running high 90's low 100's so just as an experiment to see if the senders go out of spec after a decade of heating and cooling I fit a new temp sender and it's running at 95-96 all the time now.I will monitor it for a week using the IPK readout to see if this is consistent.

[kaiser]

Either the drawing is wrong, or the system does not work as claimed. Those are the only options.
The key is the thermostat housing, which I have not seem.
The specific question is where the lower disk sits with the thermostat closed. If it is proud and not closing the hole, the system cannot work as claimed.

This is quite elementary.

[ceedy]

Well this morning has a special private Session in my Mates garage .

Pumped up the the Cooling system and it would not hold anything for more than 20 secs .

Found a very tiny leak out of the bottom of the inlet manifold. ( possibly the reason it had the K-seal in Historically ?? and why it took 3 weeks to lose enough water to pop the overheat warning )

Whipped it off and fitted a new gasket.

Pumped up and it held a good pressure for over 15 mins ..so no leaks

Then we vacuum filled the system with Red anti-freeze mix , and warmed the car up for a while.

All pipes get hot and the rad is warm all over.

Drove home ( only a couple of miles ) and it was up to over 100 by the time we got back . .

Had to pop off to a small car show at 12 , but when I got back at about 17:00 , the system was still holding the pressure .

So getting nowhere ..

The fan does come on at 105 as shown on the IPK , but just wondering if the sensor is telling porkies to the system ? .
I have the sensor I took off the Diesel with its cool running, and that made no differnece to the displayed temps so is probably ok .


Chris