Thermostats

Are there two different temperature freelander thermostats 82degrees C and 92 degrees C.

I've just installed one from eurocarparts and have just seen one of there ads on ebay that says it's 92 degrees.

Do i now need to remove this thermostat as i had to return a faulty one yesterday, how can it open at 82C when it's listed at 92C

See screen grab of ad

Grey one opens at a lower temp than the cream colour one - at what temperatures I don't know but I was advised to fit the grey one - alls well

Wished i'd known before i'd fitted it that it didn't open at 82c, i'll whip it off before i go to work in the morning and try get a refund, they shouldn't be selling them there not fit for purpose.

The right one that opens at 82C is part number pel500110r.

It's all a learning curve.

I didn't know either till Mr Freelaner put me right

It's not just the temperature that is different. The grey stat has a softer PR bypass spring so that it opens at a lower engine speed. This is what helps the PRT do its job on the K Series engine.

Nodge68 said:

It's not just the temperature that is different. The grey stat has a softer PR bypass spring so that it opens at a lower engine speed. This is what helps the PRT do its job on the K Series engine.

Click to expand...

All good stuff Nodge

Study.....


How does the PRT work?

Conventional thermostats - as fitted to all MGFs and early MGTFs - open purely in response to temperature on the inlet side. As temperature of the engine increases, the thermostat bulb moves to allow flow through the thermostat to permit the entry of cold water into the engine. The PRT is a little different. A PRT thermostat, in addition to opening in response to temperature, will also open its value in a manner related to engine speed - which is rather given away by its name (PR = pressure relief). In effect, this is predicting a temperature rise, as increasing engine speed means that the engine is producing more power, and more power invariably means more heat that the cooling system will have to deal with. This opening of the PRT is accomplished by a simple comparison of inlet and outlet pressure, which is achieved mechanically by a balancing spring. When the engine's water pump spins faster (with higher engine rpm - remember it is mechanically driven off the cam belt) its inlet pressure is pulled down a bit and its outlet pressure rises. Therefore a pressure gradient through the entire cooling system develops and increases as engine speed increases. As the thermostat sits in the middle of that system, it therefore sees a higher pressure difference as speed increases. In order to minimise pump inlet depression the PRT therefore opens at a trigger pressure drop (determined by the aforementioned valve spring) - which for a particular system this pressure drop will be found at a fairly constant engine speed. Different engines will use different springs to suit the application - so using a PRT from a completely different engine will not be advantageous, but one developed for any 1.8 litre K-series ought to be fine for any other...

Very informative and fits perfect with my experience of three new thermostats from two different companies that did not function properly.

The label on the box said it was for rover, mg, honda only found out it opened at 92C after fitting the second one, the first was just about to blow coolant out of the bottle, the second got upto 96.3C and i switched off, the third thermostat from another company that was supposed to work as the part number pel500110 crossed referenced on there computer with the one they had in stocked and it was rated 82C, this did not work properly and did not open at all as the temperature got upto touching 100C so i switched off before coolant blew out, this had honda on the label as well, it seems parts companies sell generic parts to fit different cars with multiple parts numbers that simply don't work and the staff at the two big parts shops didn't know why or what they were selling.

It was fourth time lucky with a real thermostat, part number pel500110, grey body and 82C for the freelander, it works perfectly and thats down to the knowledgeable people on here who have given me good advice.

I'd also like to say a massive thanks to every body on the forum who's helped me out with info while i've been doing the engine on my car, head refurb, new head gasket, thermostat and coolant problem, she's now back up and running, i've driven the old girl a couple of times locally, so a MASSIVE THANKS.