Radiator temperature

[Dominic]

Campbell, your water pump is 100,000 miles old (about 250 million revolutions of the water pump) ... it may well not pump that well at idle

Holding 2,500RPM in neutral for 5 minutes should certainly bring the temperature up close to fan operating point, and it is worth making sure it kicks in now and then.

Cheers,
Robin

Might try that for mine to check the fan.

The manual tells you to do that after bleeding the system...thought you had a copy?

I do, but I could not get the system hot enough for it to kick in. Will need to sit revving it for a while to get it up to high enough temp.

[robin]

It's not unusual in S1 to not be able to get it hot enough by idling - be sure to set the cabin heater to cold to minimize heat loss through the matrix ... S2 had worse circulation through the rad (smaller dia pipes, maybe?) and so gets hot at the drop of a hat

Cheers,
Robin

[Dominic]

It's not unusual in S1 to not be able to get it hot enough by idling - be sure to set the cabin heater to cold to minimize heat loss through the matrix ... S2 had worse circulation through the rad (smaller dia pipes, maybe?) and so gets hot at the drop of a hat

Cheers,
Robin

Must mean that if Campbell's will get hot enough it's fooked

[campbell]

It's been the same way for years!

[Ferg]

Just as it's not been mentioned, jacking up the car in the near side makes a significant difference to how well you can bleed the air out of the front bleed point.

Mine will get to fan temp in about 10 minutes idling at standstill.

[jammacdo]

good idea thanks

[jammacdo]

Have ordered a remote thermostat. I reckon my thermostat is sticking as it still doesn't open at more than 90c (thats the hottest I can get it in these ambient temps) And the more I read about thermal shock the more I think the remote thermostat with a pressure/temp actuation is a good idea. Of course thats before I actually fit it.

With 90c+ reading on the Stack and a freezing radiator it really doesn't add up to an ideal situation for the engine. Will find out if the remote setup works better.

[robin]

I don't think you understand how the thermostat works. If you cannot get it any hotter than 90C then that's because the thermostat IS OPENING.

If you want to prove that, clamp off the return hose and you'll soon see 125C on the temperature gauge

Trust me, the engine requires cooling, even at idle, and if your stat is stuck shut it will boil over in no time at all.

If you want to go down the remote stat route, the only approach that has technical merit (IMHO) is the PRT kit. It's a ball ache to plumb in, and only required if you don't warm the car up/use it on track.

Cheers,
Robin

[Ferg]

The temps on the dash versus the radiator touch does sound odd. Have you replaced your temp senders? After reading various temp related threads dodgy senders was often an issue. For a relatively small amount of money, changing them both is dead easy and will give you more confidence in the reading on your dash. Just an idea, you may have done so already.

[jammacdo]

Thanks guys.

Robin I understand what you say about the thermostat. I've rebuilt enough cars (all FWD though) to understand the cooling principles. But the reality is that according to the temp gauge it cannot get hot enough (93c max and no water flow). However when I reach inside and touch the offside of the rad its roasting hot (too hot to touch) but the opposite side is freezing cold. Basically there is no water flow. If I touch the pipes near the expansion tank they are also roasting - like in the 90c range.

I suspect the thermostat is stuck - or perhaps needs to be REALLY hot to open and that fact that its so cold outside and I've been moving (not in traffic) is why its not overheated. I bought the PRRT from EliseParts. Will fit and see what happens.

Good call on the temperature sensors, may change those as well.

[robin]

If the stat is not opening, then where is the waste heat from the engine going when the car is under load?

There are two reasons for the temperature to level off (ignoring the possibility of the temperature gauge simply being bollocks) - thermal equilibrium and regulation-by-stat. If you think the stat is not opening then you must be hitting thermal equilibrium. In that case, increasing load without increasing cooling should make the temperature rise.

When the car is rolling along the airflow across the rad and chassis will make it hard to reach equilibrium because it (and engine load) will always be changing.

Instead, open the throttle with the car stationary. 2,000 RPM gets you to perhaps 90C according to earlier data - now increase to 4,000 RPM - you've just doubled the waste heat the engine produces; if the stat is stuck then the engine temperature must surely rise in order to once more reach thermal equilibrium. Back of the fag packet fisics say that heat loss is proportional to the temperature difference - so if ambient is 10C, 2,000 RPM's worth of heat requires 80C above ambient, 4,000 should require 160C above ambient = 170C; of course you cannot get to 170C in the cooling system - the fan should kick in first (regardless of whether or not the radiator is hot/cold - the fan is controlled by the coolant temp measured at the engine).

Sooner or later, in neutral, at 4,000 RPM you should see the fan cut in (or not, if it's long since seized). There is nowhere else for the heat to go ....

But on the elise, especially S1, there is a lot of conduction of waste heat to chassis - so you may find the chassis rail on the driver's side gets pretty hot before you can force the temperature of the engine to rise above the stat regulation point and eventually trigger the fan cut in.

It is also very easy to demonstrate that the stat is working, by doing something similar from cold - start the engine and once you've got a bit of temperature indication on the dash, give it 2,500 RPM and leave it there. Note down time vs temperature. You should see a pretty linear rise to somewhere between 85-90C. Then the temperature will level out and stay there. That's the stat doing it's thing ...

Feel free to change it all, but I remain to be convinced that you have anything other than possibly an airlock in the radiator.

Cheers,
Robin

[tut]

On the S1 if you suspect the fan is seized, you can reach through the grill with a long screwdriver and try turning the fan blades to free it.

tut

[jammacdo]

Robin

Thanks for all the explanation! I will try that out tomorrow. Which will be without touching anything. Airlock? Huh, probably that...again

The rad fan is brand new and isn't stuck so thats one less thing to worry about