190 sport temp gauge

I am looking for some help regarding a temp. gauge problem on my 190 sport.Normal driving the temp. gauge remains around 83/84degrees, in traffic, gauge goes up fan cuts in everything ok.As soon as you start to drive the car hard the temp gauge goes down and on occasions has gone off altogether, usually the temp goes back up when you lift off but has sometimes taken a while to register again.Have changed both sensors, 1 blue 1 black and have even had stack changed under warranty, would be very grateful for any advice.

Same thing happened to me and led to a HGF later.
Your thermostat is fcuked. It’s either stuck in the open position or the spring is so weak that it just flows.

Recommend to change it now to a remote one, either by QED or Eliseparts.
It’s a b!tch of a job, you need double jointed long fingers, May be worth to give to a dealer to do.

removing the old thermostsat is a job i don’t want to do again, hence the remote one installed, I would go the dealer route and save hassels.

Uldis, I agree the thermo is a bad set-up (I’ll switch to a remote one shortly) but are you sure it’s definately gone? This type of thing happens to me normally. The cold coolant from the rad isn’t let through until the car is nailed and the temp then drops (although mine doesn’t disappear altogether). From past posts, I thought this happen to most Exiges?


Well, he has changed the sensors, so that’s not it.
OTOH, the symptoms are all there for an open thermostat: when stationary, there is no airflow and the engine manages to build up some heat, even if the thermostat is always open.
When airflow begins, the radiator is cooled, and this cools the system… too much. The temp starts going downa nd I remember I was driving in the Motorway at 48 DegC
I would imagine it could even drop below 40 in this weather.

It could be that his failure is something dofferent but fits this scenario as far as I can see it.

Does your drop so much? because what I understood happened to several Exiges was that the temp dropped by about 5 degC, not even 10.

Bear in mind that driving the car cold is one contributing factor to premature HGF…


Not sure if it helps but my temp gauge was doing similar things last year shooting up and down,

Mine was unfortunately HGF.

My dealer checked the water for oil fumes and it took him all of 2minutes and didnt need to do a pressure test.

Might be worth getting it checked, At least if it isnt HGF, you could rule it out and then start looking at other possible causes.


Does your drop so much?

Mine can get into the low 70s.

Geoff, is yours going below that?


I think your thermostat’s spring is weakened already, you should change it now, before you damage the HG.

Many thanks for the advice,the gauge does on occasions go off altogether,sometimes coming backup straight away,other times stays off for a time which means the rev limiter kicks in at 6000 and the tickover increases.Because the car is still under warranty I have decided to go down the dealer route.Problem is the only dealer in South Wales has given up the Lotus franchise, I think it ends in December so they are not stocking any bits, so they are ordering an 82degree stat and will try that when it arrives, again many thanks for the advice.

I forgot to mention that the metal pipe at the bottom of the engine bay (the one with the 8mm. bleed nipple) never gets hot only slightly warm, could this have any relevance?

That is the pipe carrying the coolant to the engine. That is the temperature the coolant is going into the engine.

Very bad if it’s cold. Either not circulating properly or it’s just as I was saying, being cooled too much.
I suppose when stationary and the fan kicks in that pipe is hot, right?

If not, you should not use the engine until it’s sorted.

Thanks uldis I tried what you said, I got the engine warm let it tick over and about 90degrees the coolant pipe got very hot and just after the fan kicked in.So going with what you said it does seem that the engine is being overcooled and it points to the thermostat.Thanks for your help.

Ian - do have con air ??

I thought remote stat was not feasible on a con air set up ( recirculating pump )

No air con, no music wanted it as light as possible.

Ian - do have con air ??

I thought remote stat was not feasible on a con air set up ( recirculating pump )

Yes and “Oh!?”.



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Or moving of the coils more towards the rear of the car (as I had to do)
You can check my pics on my bookatrack gallery.

Theres more to it than just the pipe moving …

On the air con car there is a vacuum water valve where you would fit the remote stat and this cuts the hot water supply to the heater matrix.

Also there is a recilculating pump in the circuit that pumps from the engine outlet back into the thermostat housing. This pump hopefully stops localised overheating when the engine is turned off …

Ian, my temperature can drop to 70 or so when reved hard until it balances out - I tend to drive a very conservitive couple of laps until it stops that

And here I was thinking that either a remote or one of the new housings would make a good winter project for my air-con car
Is there no way of ‘upgrading’ the cooling system on air-con Exige? Will the new Rover thermostat design and housing fit and/or make any difference. Anyone know?


I’m with you Mike!