Temp gauge

[andyblackman777]

Hi,

My temperature gauge wavers around a bit sits at 90 most of the time then slowly drops sometimes as low as 55?! I replaced thermostat and rad cap and its the same. my Digimo software running from ODB port reads temp as 90 steady so i"m guessing its the gauge. Anybody had similar experience

cheers Andy

[snuffy]

Hi,

My temperature gauge wavers around a bit sits at 90 most of the time then slowly drops sometimes as low as 55?! I replaced thermostat and rad cap and its the same. my Digimo software running from ODB port reads temp as 90 steady so i"m guessing its the gauge. Anybody had similar experience

cheers Andy

<{POST_SNAPBACK}>

Mine does the opposite. It sits at 80-85 then creeps up tp 120+ then within about 2 seconds drops back to 80. My GT3 did the same thing. It's going in for a service next seek so I'll get them to fit a new sender.

[neal]

Mine does the opposite.

Edited June 2, 2006 by neal

[andyblackman777]

Ah didn't realise the odb uses a different sender to the gauge !

cheers Andy

[snuffy]

Ah well, what happened a few weeks ago was as you described. It crept to 120 then dumped a load of water on the road. Uncle Superdave fitted a new thermostat for me, which took about 45 minutes or so. No problems for a while but now every so often it goes 120+ but then returns with a couple of seconds. If the thermostat was sticking and then opening at 120 the temp would not come down that quickly. Also, the over temp light on the dash does not come on and the fans may not start, so I think it all points to the sender.

[neal]

Ah well, what happened a few weeks ago was as you described.  It crept to 120 then dumped a load of water on the road.  Uncle Superdave fitted a new thermostat for me, which took about 45 minutes or so.  No problems for a while but now every so often it goes 120+ but then returns with a couple of seconds.

If the thermostat was sticking and then opening at 120 the temp would not come down that quickly.

Really, it would. The coolant 'capacity' around the engine is well less than half that in the whole car. So with the coolant around the radiator at ambient, say 20'C (it's quite a nice day here for once!) and your 'engine' coolant at 120'C, they'd meet in the middle - 70'C.

Also, the over temp light on the dash does not come on and the fans may not start, so I think it all points to the sender.

The high coolant temperature on the dash, where the low coolant starts flashing is set very high, if I recall 115 or 120'C.

But since you've changed the thermostat you might well have an air pocket in the coolant system which 'surrounds' the thermostat and prevents it opening. Have you bled the radiator valve (hex bolt in the LHS front wheel well at the top of the radiator) and the water pump intake bleed (inset hex spanner plug at the left front of the engine) ?

But I'm *very* interested as to how you get on.

The 'dumped a load of water on the road' is exactly what mine is doing on ocassion and eventually results in a low coolant light - but it's been much better since I replaced the thermostat.

The car's been to Lotus themselves on two occasions for this and they did *F* all. Got it back with exactly the same symptoms. They replaced the expansion cap. But when I pressurised the system using a a tyre inflator hooked up to the overflow pipe from the expansion tank, that cap couldn't hold a single psi of pressure. *IDIOTS*. They offered to take it back a third time back in April, but low and behold I haven't heared a word since - and to be honest I don't want to - I've done a lot more to remedy to the problem than they ever got to

I've replaced the expansion cap with a proper race one which does hold the pressure. Then drained the coolant system so I could see how it held up under air pressure - not water pressure. This is significant since when the engine cools the coolant contracts and the idea is that it draws coolant from the overflow tank back into the expansion tank. But if you have an air leak, it just sucks air in instead. Bad!

Found two air leaks

First was the bleed valve on the radiator. It's a 'stub' bolt so has no sealing at the hex top. I replaced with a proper hex bolt which locked in place. The other leak was at the coolant pump intake hose (LHS) intake circlip. Couple of turns more and it was solid.

Now I can pressurise the system up to 30psi (the cap/stock is 20 psi) and it holds. So definitely no problem with the liners, etc. But the thing is it still pisses coolant onto the road every so often and I'm out of ideas!