Thermostat stuck open??

[Ray Pearce]

Post Dunsfold my car (1.6 K) seems to be failing to get up to normal temperature.

 

Driving on open roads I am seeing about 50^o. When stuck in a queue it climbed to 65 but then fell back again when I started moving. When I got home I let it run while stationary and it climbed over 80 and the fan cut in as expected.

 

Am I right that this all points towards a thermostat that has stuck open?

Several threads on here have confused me about what thermostat to get, the standard Caterham ones seem to be 88^o is this the one to use?

 

 

[charlie_pank]

Symptoms sound like a stuck thermostat. Drain the coolant, take it out and have a look at it - the last one I looked at that was stuck has a bit of solder from the radiator holding it open. Clean it up and stick it in a pan of water. Bring the pan to the boil and check that it opens at the correct temp, and that when you take it out it closes again. If it all works fine, stick it back in, if it doesn't, have a look at the markings on it, which should tell you what temp it is supposed to open at, and order another.

 

 

 

back here because I want to be.

[Steve-B]

Hi Ray,

 

If yours is @£$%^ered, consider going to the 78C - 82C Rover Diesel one which works perfectly well in any K engine if you've got to change it? Keeps engine cooler, kicks in sooner. Only tiny downside is slightly less heat from heater if you have one in Winter. FWIW you might also consider going to the VW fan sensor whilst at it, so you've got a more reliable cooling system. Both P/N's can be found via searching the archives.

 

 

[Mick Day]

Don't use the 78 C thermostat as it'll never warm up properly in our climate: it'll be like a stuck open thermostat all over again. Use the 82 C version, Halfords HTK 605.

 

To check if it's stuck start the engine from cold & check the temp of the rad. Will get warm far too quickly if stuck open.

 

Ditch the rad thermoswitch & get the fan switched from the ECU.

[CageyH]

Will 4 degrees make that much difference?

I would use the 82 degree version, as it is further away from the 88 degree fan switch.

 

If the thermostat is at 88 degrees and the fan cuts out at 88 degrees, does that mean that the fan runs until the thermostat closes? Will this give thermal cycling?

 

Only dead fish go with the flow....!

[heavenly7]

While you are about it I would fit the external thermostat - it is easy enough.

 

I never thought it would make much difference.

 

However it was interesting to see with the Spa digital gauge the extent to which the temps were all over the place as the engine warmed up and during periods of idle.

 

With the external stat it is almost spell binding to watch the temperature climb to between 85.6 and 87.2, the stat to have opened and the temperature fall back to within a degree of 85, and having got there, stay there.

 

I am almost convinced it is the single most significant upgrade towards preserving the HG and generally looking after your engine.

 

Edited by - heavenly7 on 9 Jun 2010 17:31:36

[Mick Day]

Will 4 degrees make that much difference?

. It did with my engine in 2002 when I uprated the cylinder head. I went from a 88 to to 78 & Steve Greenauld had no end of problems getting the thing up to a reasonable temperature. He said ditch it for the 82 version.

 

Incidentally my ECU switches the fan on at 86 & off at 84. The SPA gauge seems to sit all day at about 78 & the ECU reading when connected to the PC shows about 3 degrees higher. (Which is correct? Probably neither! ).

 

The fan rarely comes on, usually only whilst stationary in traffic. The highest temp I've seen was on a hot day grinding up a mountain pass behind an artic & then the water temp got to 90.

[Ray Pearce]

I pulled the thermostat out this afternoon and found a hoge lump of grit holding it open. At first I couldn't see how to shift it without damaging the stat and then the penny dropped. I stuck it in a pan of boiling water, the stat fully opened and the grit fell out.

I hate O rings

Managed to split the original and spent about half an hour trying to persuade its replacement to fit. Is there a secret to this?

Anyway, its all back together now and seems to be working fine.

 

Thanks to all for the advice.