Overheating!!!

[andlyn001]

My 98, puma 1.7 has had temp issues. I've not let her boil up. Found that putting heater on hot and blower on4, or by revving the engine to about 3000rpm brings the gauge down nicely. I fitted new thermostat but this made no diffeUrance. I was about to use Holts 2 stage engine flush but i bypassed the heater valve first. This seems to have solved the issue. The gauge now sits just below mid way and if I leave her ticking over for quite a while the gauge goes up to the A of normal, the fan cuts in for about 10 seconds and the gauge is back down. I had previously replaced the valve 4 years ago as I wasn't getting any warmth in car. How does this valve cause overheating can anyone explain
Pl

 

[YOG]

Explained on another forum:

How does the heater valve cause overheating faults as surely the water will still circulate but not through the matrix.

It's the weird stat arrangement. The wax pellet faces the radiator, not the hot flow from the head, creating a Catch-22 scenario that the wax pellet only gets hot water to open it - once the stat has been opened.

To get round that issue; they plumbed the heater return flow all the way around the engine bay just to warm the back of the stat. Once the heater valve sticks halfway; it doesn't feed enough hot water to the stat and so it doesn't open properly - just as a fitted-the-wrong-way-round stat wouldn't.

The heater valve also contains a by-pass valve and either feeds the matrix or diverts the flow back into the thermostat housing where it goes past the wax-pellet end of the backward-facing stat and heats it. The faulty one appears to have come apart and blocks off both ways at once: hence the difference in temperature of the heater hoses in and out and the cause of the problem.

 

[Easta]

What a rare set up.I best change the hcv sharpish then

 

[alex]

another thing is does it have a leak water leak that is cos i found out my problem was the water pump was leaking....

 

[andlyn001]

No signs of a leak and the cars been fine today with it bypassed. I'll leave it like this for a few days see how it goes. Then get a new valve