K-series Thermostat. Stop Overheating & Better Heater. Change PRT to output type - Old PRT reused.

Better Cooling! MG Rover Freelander Thermostat. Stable head temperature! Better Heater! I show a new much better setup that avoids any potential overheating, keeps the temperature more stable and makes the cabin heater much better by changing to an output type thermostat (as used by racers) at no cost, just reconfiguring the PRT one!

I discuss what failure mechanism and overheating problem I have fixed with the new setup.

Second I discuss where the original thermostat is and how to change it and the rear pipe - often a source of leaks.

Third how to do a conversion to a PRT type external thermostat and what it is, plus a look at the internals and how it works.

Fourth - why the PRT setup can lead to engine overheating when idling, especially in cold air and why you may not know you have a problem.

Fifth and finally the NEW configuration - a replumbing of the existing PRT that turns it into an engine output type of thermostat that gives MUCH more stable engine temperatures and removes the previous ‘overheat on idle’ failure mechanism. It also gives a much better cabin heater.

The PRT system often appears to work ok but there is a mechanism whereby it can lead to significant engine overheating (117 Centigrade!. Which can shorten the like of the cylinder head and gasket).

To see the failure mechanism you either need an additional temp gauge or an OBDII reader as the car gauge just shows normal from about 60 to 110C! (Like most modern cars! - they don’t like to worry customers!).

After a long time idling it can sometimes overheat. I changed to another PRT and a similar overheat happened. Tried grey and biege PRTs. I split the old PRT apart to check operation. The pressure spring / plate is against the bypass flow pipe (engine out to pump inlet pipe). It is also pushed more as the thermostat opens (that makes sense in that it reduces the bypass flow when hot). The thermostat opening controls the cold return from the rad, the back of the thermostat with the sensing section has a limited flow from the spring/plate/ bypass flow with some mixing from the cold rad return when the thermostat opens.
So the stat is trying to provide a set temperature of the return water, which is a mix of bypass and rad return water, rather than control the engine out temperature like most engine stats.
Problem: At idle there is little water flow through the bypass hose as the water pressure is low and the spring /plate is closed and limits the bypass flow. The flow is restricted to 4 small holes in the plate.
This small flow of hot water has to heat the thermostat which has cold water the other side of it and the PRT is a bit of distance away from the engine. Soo.. the engine could get very hot before the thermostat eventually opens. Which is what I see happening, and its made worst by the fans coming on as the engine gets hot, as this air flow just cools the PRT and bypass flow more, which doesnt help open the thermostat.
Any revs quickly opens the pressure spring/plate due to higher water pressure, this increases hot water flow to the stat and it opens, rapidly cooling the engine with colder water. Not good either = big sudden temperature change.
So a better system is, I believe, with a engine water outlet thermostat.
This would then regulate the outlet temperature keeping it constant, reducing engine temperature fluctuations which can be bad for the HG.

An alternative is to open up the 4 holes in the spring plate more, but this allows for more bypass all the time even when very hot, which is not good. I tried this with a couple of 5mm holes, but it didn’t prevent idle overheating (110C).

The temp variation observed above was with a beige PRT, which is slightly higher temp than the original grey one, but the same effect was also observed on the grey one. I split apart the grey stat and it worked fine opening fully at 100C in boiling water. Hence why I changed to an output type of thermostat configuration.

The car never showed any problem when used normally as this overheating problem only shows on idling for a long time. Like what happened to me while the car was having an MOT test! Or stuck in traffic for 10 mins. Not good.

Due to the inherent issue of the PRT regulating the water temperature going into the engine rather than the more normal regulation of water temperature coming out, then the plan involves a replumb the PRT to make it a plain thermostat (not pressure regulated) that works on the engine water outlet.
It works and is a lot more stable.

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Видео K-series Thermostat. Stop Overheating & Better Heater. Change PRT to output type - Old PRT reused. канала comeinhandynow