more cooling problems

[fedex]

any advice welcome, first I thought it might be an airlock, but not so sure, flushed out the system with clean water, and when its idling can cleary see the water being moved around the system, it stays cool for thirty minutes at idle, then it goes to a quarter on the temp gauge, then to half way and then three quarters. All of a sudden it drops to a quarter then half and back to three quarters and stays there. I checked the expansion tank and it's empty so no back flush. just ordered a new temp gauge and sender?. I have also removed the thermostat as I thought it may be sticking.

[Ian Durrant]

Have you noticed if the fuel gauge is erratic also

[fedex]

no stays steady

[Ian Durrant]

Its very odd behaviour then, I cant think of a fault condition that would produce those symptoms if its not an unstable voltage regulator.
It could be the sender I guess but I haven't seen one fail that way. Someone like Russ (kryten) who did this stuff for a living may have more idea of the rarer failures.

[RNF]

Do you happen to have a infrared laser temp gun? under £20 and great to verify actual temps.

[staginhiding]

Still sounds like air in the system for it to show a drop in temp after its got so hot..
If it had got to normal running temperature and it was idling,then got very hot it is unusual for the temp to drop to a quarter again..

Definately sounds like you need to check the gauge,sensor and infrared the system..

Did it do exactly the same after you took the thermostat out ?

Sam

[flying farmer]

Sounds very much like a sticking thermostat.

If you can see water moving through the rad filler plug with the engine cold then the thermostat is stuck open as it should be recirculating through the block and not moving through the radiator.


I have come across the phenomenon of the temp gauge going over the normal running temp from cold, then dropping back again before rising to normal running temp several times before on other Triumphs. This is normally caused by the thermostat having no jiggle pin, or no bypass on the centre disc of the thermostat (often just a couple of slight kinks in the outer disc of the thermostat to stop it sealing completely. What happens is the lack of circulation past the thermostat means that when it finally opens it does so quickly, dumping all the cold water from the radiator into the engine which causes the temp to drop again.

Start with a new thermostat, but make sure it has a foot if it is a mk2 inlet manifold, no foot if it is a mk1.

I have found from experience that Halfords only list one thermostat for the Stag and say it is suitable for both, it isn't!

Neil

[Ian Durrant]

I was thinking the same as you Neil, but unless I misunderstood his post, its happening even with the stat removed.

[Stagsongas]

Might not be relevant, but didn't Kryten show that removing one of the two distinclty different types of Thermostat can actually result in overheating by opening up the bypass, thereby sending hot coolant straight back around the system?

Or perhaps it was only if the wrong type of thermostat were fitted to an inlet manifold it was not designed for?

I forget which type (foot and no foot) was which. I only have one type of Stag inlet manifold fitted to one Stag, and it has no thermostat anyway, so maybe someone else can give chapter and verse, or perhaps you would find the info. using a search?

It just could be that the orginal thermostat was indeed sticking, and it's removal has made things worse, not better.

Regards

Steve

[V Mad]

The Mk2 has a foot which blocks off the bypass. But the Mk1 does not, so presumably the bypass must be open all the time, yet it does not necessarily overheat (mine certainly doesnt).

So it begs the question that if the Mk1 always has an open bypass, why should the engine overheat if the thermostat is removed?

[wilf]

Is it gravity?

[staggering]

Chaps, although I am RV8, when I first had the stag I was getting 95 / 100 on hot days. Thought I'd check the thermostat etc, only to find the PO had removed it. Fitted a new one and has been regularly 80 - 90 year round. Been told that without the stat the coolant is travelling "too fast" to give all parts of engine good heat transfer to cool - just my exp of no thermostat being fitted causing problems.

Cheers
Ian