Running temprature

[Alec]

Hello Mike,

considering the small amount of heat generated when standing still compared to when the engine is loaded when on the open road when the temperature is normal, it would seem unlikely that the radiator is the problem.

Although Ian seems to indicate that changing the coolant and new thermostat has improved things, it still doesn't explain why it overheated when idling and not when running, that is rather upside down?

Alec

[Mike Stevens]

Hi Alec,

Well, yes, although it's true that the excess heat is less when idling, there is also no ram-effect air cooling the radiator, but which one has the most effect - I don't know. I've certainly had issues with overheating when sitting idling but Ok when moving and that was a radiator. The car too!

Checking the temperatures should give a clue one way or the other!

Cheers,
Mike.

[peewee21]

Well I looked further into this

Agree that there is less RAM affect but there is also fewer RPM when stationary so the fan is spinning slower.

did an electronic idle RPM check and it was turning over at nice slow 400, i have increased this to about 900 so the fan is now spinning at twice the speed.

this should also help

[Alec]

Hello Ian,

400 rpm is very slow for an idle speed, not only is the fan running slowly so is the water pump so very little water flow around the radiator.

Alec

[peewee21]

True Alec

interesting thing now after a test run is that its new norm appears to be about 60-65% instead of the steady 50% prior to the work. though not getting any higher.

may need to look at the tuning, such as timing, fuel mixture and carb balancing etc after the idle speed increase

[Vox]

I am having exactly the same symptoms and would really like to know the answer to this one!

When I got my 72 mk2 a couple of years back it overheated fairly easily but flushing both ways with and without proprietary flushing stuff, all new hoses, water pump (Chris Witor), thermostat and rad cap (13lb instead of the 7lb it had) made things loads better but could still start to run rough when really hot and then would start to climb on the guage but not as fast as before.

Then managed to pick up a (supposedly) NOS radiator of the larger depth type which I thought was the end of it. Still does it occasionaly if stuck in traffic (particlarly yesterday when it was 37 degrees but even when not that hot). When it starts to run rough (which is before the gauge starts to climb) it seems to be because it has gone way too rich - taking the plugs out show them to be very sooty wheras most of the time they are showing if anything a bit on the lean side but ok. This seems to be confirmed by if you come back to the car when hot in normal use (when hasn't been overheating) after 5 - 10 minutes it usually requires the throttle to be floored to get it to start but there is no sign of flooding. Adjusting the carbs to be OK when really hot means they are way too lean the rest of the time - to the point of being undrivable.

It may or may not be connected to a new thread I am just about to start about the differences between static and strobed ingnition timing.

I know a Kenlow (or similar) fan would help but to me that is curing the sympton rather than the problem and with everything new it really should work as well as they did in the 70s! Once you get moving again it soon cools down back to normal.

Chris

[Alec]

Hello Chris,

does you car have S.U. carburettors with the wax stat temperature compensating jets, which could explain the variation in mixture? I think the general consensus is to do away with wax stat jets?

Alec

[Vox]

Hi Alec,
No, mine has the Strombergs with the mixture adjustment through the dash pot.
My previous Doly (1981 model) had SUs with waxstats which we were always having to fiddle with - I remember my old mate the late Len Young (local Triumph expert who used to do my welding and MoT) ended up doing something like aralditing a penny in the stat part to get it through the emmissions part of the Mot one year...
Chris

[Alec]

Hello Chris,

I'm very familiar with S.U.s but not Strombergs so I can't advise on those.

Alec