Hi
I am runing a Lotus twincam engine with a Davies Craig electric water pump and controller.
I have never had an overheating problem but when it was 24 deg C external air temp, the engine was running in the early 90 degrees (F - I am struggling with this metric lark)
The engine likes to run in the early 80 degrees (F) and was unhappy running too hot.

I have already fitted a diode to drop the pump flow operating range by 10 degrees.

In diagnosing the problem, it did occur to me that I am running a pressurised system but the expansion tank is set at the same height as the middle of the block.
Does the expansion tank need to be the highest point on a sealed system? (and could this be why my heater doesn't work too well)

If I can't sort it out, I'm going to resort to the engine's water pump

Thanks
Gavin

80F is very cold, only 26C (room temperature) are you sure?

o.k reading again I think you mean 80C normal, 90C running to hot. To me 90C does not sound to hot (but I am no expert on engines!)..

As to the expansion tank position it should not matter, the only problem is if you have gas being introduced into the system, it will tend to go to the highest place.. Ideally it would thus be better at the highest place, so a small gas leak (headgasket) would not expel you coolant from the pressure cap..

From your symptoms I suspect you have an airlock one option is to add a small bleed to the highest place and bleed the air out under pressure.. My heater feeds are the highest so have two bleed points there, might be worth a try. When I re-fill the system on the first engine run I bleed the air out once warmed up, or I pressurise the system using a hand pump on the air bleed hose back to the header tank..

Dan

[Edited on 8/11/11 by Bluemoon]

[Edited on 8/11/11 by Bluemoon]

Just a thought,
What thermostat have yoy got in there?
Might be able to try a lower one.

[Edited on 8/11/11 by tony.g]

90 is fine, i would be happy with that

expansion bottle or header tank?

both very different things, expansion bottle doesn't matter where it is, header tank has to be at the top

you say its pressurused though, so it sounds like a header tank, so it should really be near the top of the system

[Edited on 8/11/11 by blakep82]

The header tank/expansion bottle postion will have no effect on circulation

For the heater to work you need a thermostat fitted --- or at least a restrictor plate where the thermostat was originally

Lotus-Ford Twicam water pumps are a pain to work on but I can't help but think that are a much better than any electric pump.

90c isn't high even for an engine of this era the original thermostat would have been an 82c unit --- ie. 82c is the temperature the thermostat starts to open.



I would sugest the following
(1) Check your temperature gauge is reading correctly.
(2) Revert to the orignal water pump.
(3) Fit a thermostat with a few small by-pass holes drilled in the stat.
(4) Lotus engines are very susceptible to running hot due incorrect ignition timing.

The system runs under pressure and it is definitely an expansion tank... I'm sure of it

The thermostat doesn't exist - I had to remove it for the electric water pump system but I did retain the ring.

I think the optimum temp for a twink is around 84 dgrees - no idea why but there has been a lot of research carried out on it (not by me - I wouldn't know where to start). it might be linked to the oil system because being an older design, it runs much looser tolerances than modern engines.
Either way, it was less and less happy the higher the temperature rose and when the temp dropped, the crispness of the engine returned.

Any more clues greatfully appreciated.

Thanks
Gavin

If you took the thermostat out, i doubt the temp would even get to 70, let alone 80

I would suspect the gauge is not reading correctly, just like my setup, temp gauge reads about a 1/4 in,
and only rises to about a 1/3 in if i cain the engine to an inch of its life

And my clock set, came from a lotus elan 2+2 , that i broke up 25 years ago

regards

steve

Steve

The gauge was rebuilt about 4 years ago

And there was definitely a performance change...

Thanks
Gavin

The performance change is likely down to air inlet temperature, especially if you aren't running the original air filter which was fitted in front of the rad to get cold air.



[Edited on 10/11/11 by britishtrident]