Engine Temperature

[jeeves]

Yes it does have a prt type I have no experienc of this type but have had normal ones that stayed open not letting the water warm up quick enough it's just me having to rely on garage not a diy sort it still hasn't used any water since but runs a bit hotter

[T-Cut]

Originally Posted by SD1too

Yes you have T-Cut, on the M47R engine!

The troublesome diesel stats always close (as Jules will confirm). They run at progresively lower temperatures because the stats begin opening early. You clearly haven't read my research. The only way a wax stat will not close is if it's wedged open by debris of some sort or it's mecahnically damged/bent. The high tension return spring always closes the valve if the capsule 'fails'.

TC

[T-Cut]

Originally Posted by jeeves

Yes it does have a PRT type. I have no experienc of this type - - -

The important thing is do the garage have any experience of a PRT? Did they know the later 1.8s have this type fitted?

A 1.8 displaying rapid heatup and overheating after a garage has replaced the thermostat rings bells loud and clear.

TC

[Yorkshire GOC]

Was there not a spate of incidents where garages fitted an early thermostat onto a PRT set up - so 2 thermostats causing all sorts of problems - has been a few years since i have heard this happening but you never know.

[SD1too]

Originally Posted by T-Cut

... because the stats begin opening early.

Ah yes, so sorry, I must try to remember this!

You clearly haven't read my research.

Rest assured that I am an avid reader of your research on the petrol engine fuel tank system, the workings of the expansion tank cap and your clarification of the IPK diagnostics. I have to admit to being a little less enthusiastic about diesel thermostats, hence my momentary lapse of memory.

Anyway, I hope that the experience I've had of failed thermostats in the open position on the A series engine is of interest to you.

Simon

[T-Cut]

Originally Posted by Yorkshire GOC

Was there not a spate of incidents where garages fitted an early thermostat onto a PRT set up - so 2 thermostats causing all sorts of problems - has been a few years since i have heard this happening but you never know.

I believe it's an ongoing iproblem. Customers with a 1.8 PRT system who receive an additional stat following a garage 'repair' will get overheating issues. Many never realise what's afoot and either live with it or eventually visit a forum like this. There are umpteen threads from newcomers describing cooling system troubles long after the event that caused them. Many (most?) garages don't and never will understand the unusual features of 75/ZT engines.

TC

[T-Cut]

Originally Posted by SD1too

Anyway, I hope that the experience I've had of failed thermostats in the open position on the A series engine is of interest to you.

Blimey! They used the bellows type didn't they? If a modern wax propelled stat ever fails open, I'd love to confirm the reason (see below). There are some, rare 'fail safe' wax stats that latch open permantly after a dangerous overheat. But those don't count, because they haven't actually failed of course. I've seen wax stats fail to close on cooling due to mechanical damage caused by the owner and also from debris jamming the valve open. Normally, there's nothing that can prevent the very robust return spring from closing the valve. However if the wax gets expelled from a poor piston seal and coolant enters the capsule on cooling, then it might hydraulically lock it open. There's reference to a patent to prevent this in my diesel thermostat thesis. I guess that's what happened in your A-series before stat piston designs had evolved very far.

EDIT: Old Patent synopsis:



TC

[SD1too]

Originally Posted by T-Cut

Blimey! They used the bellows type didn't they?

You might be right in the very early days but by the time I reached car ownership age the 'A' series was using Waxstat thermostats.

Simon

[kaiser]

Originally Posted by T-Cut

The troublesome diesel stats always close (as Jules will confirm). They run at progresively lower temperatures because the stats begin opening early. You clearly haven't read my research. The only way a wax stat will not close is if it's wedged open by debris of some sort or it's mecahnically damged/bent. The high tension return spring always closes the valside ve if the capsule 'fails'.

TC

I have had a thermostat fail open. Not bent and not jammed by any outside debris. It is btw the only thermostat I have had to replace under warranty!
Fairly new one at that!
But most will fail to open properly - eventually, I will grant that.

[T-Cut]

Originally Posted by kaiser

I have had a thermostat fail open. Not bent and not jammed by any outside debris.

Pressurised leakage of wax past the piston seal and subsequent ingestion of coolant into the capsule seems a likely explanation. It was clearly an issue at the time the mentioned Patent was granted. Can't remember the year, but I reckon 1960s or 70s.

TC