115 degrees!!!

Hi Guys,

Slight prob I think, After driving the beast yesterday afternoon for about 20minutes I looked down at the temp guage and to see it reading 115 degrees

I slowed down, about to pull over when all of a sudden the gauge went down to about 78 and then slowly back up to 85!

I hadnt been stuck in traffic and at the time it was just starting to snow so the air cooling the rad was pretty cool!

I dont think it was a faulty reading as I looked over my shoulder to see steam coming from the header tank My own mobile sauna

When I got back there was coolant all over the air filter pipe but the level in the tank was ok and the temp was back to normal.

It sounds like the thermostat sticking to me but has anybody got anymore ideas?

or similar HOT experiences? And no not the ones that invlove nans!



Ps - Is it a pig to change?

Keep a very close eye on it, this is one of the symptoms of HGF
It could also be something simple as a faulty temp sender or leaking coolant tank cap.

Where is the coolant level now (when its cold) and where was it before you started? These cars have a habit of finding there own coolant level but as a guide the ‘low’ mark should read ‘cold level’.

Oooo Errrr

If its the stat then it’s not to difficult to change,

Drop off bottom hose of to drain some (not all) of the water out, make it easyer to change and less bleading of the water when you refill it.
Stat is in a black plastic casing below the inlet manifold and fits directly onto the back of the water pump, Easy Eh!

If you are into doing a slightly bigger job then go for a remote stat set up will work more efficiently if your stuck in trafic.

Hope that it’s a simple fix, Could it be the dreaded HGF , Hope not.

Oh, let me have your E-mail and I’ll send you some info.



To rule out ( or in ) HGF get Mattys or Whales to “sniff” the header tank - they can tell if you have a problem because combustion gases will be present ( I guess you will check the oil for coolant mix - “mayonaise” yourself !)

You havent been hoovering up leaves like Uldis have you


The coolant level always used to be in the middle of the low and high marks when cold and rised a couple of cm’s when hot.

But a few weeks ago the level seemed to drop suddenly and I had to top it up, there was also coolant on the air intake pipe but its been ok ever since until yesterday.

I thought initially when it dropped a few weeks back that the hose was lose on the n/s of the rad. (I had to fix it when it happened on my Elise which I was told was a common problem) but it is ok.

I havent checked the level now its cold as Ive been at my girlfriends ever since.

I guess it will have dropped a fair bit again.
Should the cap on the header tank let any water out?


I think I’ll get a thermostat and change it.
Thanks for the advice on fitting, Ive just had a look in the service manual too and it doesnt look too awkward a job
Is it just a case of topping the coolant up afterwards or do you have to bleed the system?

If it is the HGF luckily Ive still got warranty which covers virtually everything on the car inc the Head gasket (Thankfully) but for little things like the thermostat id rather do it myself and know its been done properly!

I’ll send you my email.

Cheers Paul


Just thinking … I also had a header tank cap problem - caused something like you have - a new cap fixed it …

The tank cap should’nt leak under normal use but a number of them have been known to go faulty and open up at a lower pressure and let coolant out. I think a replacement is a few quid from your Rover dealer.

As Andy says have you checked your oil for any signs of water contamination and also take it to a garage to sniff the coolant tank for exhaust gases.


When I get back tomorrow I’ll have a look at the oil and pop round to see my mate who works at matty’s.

I know he’s replaced quite a few head gaskets at work so he might be able to help me out.

Anyway, Im off out up Broad Street tonight on my work Xmas do so I’ll drown my sorrows again

If Oultons anything to go by, I bet I wont get up in the morning




Not much I can add to what the others say above… however, Uldis is having a look at replacing his thermostat, so he might offer advice if you choose to do it yourself, however, if you have warranty why not get it done at a garage?

Also coolant tank caps are cheap so you should maybe replace it anyway… I think its the same as an MGF, anyone confirm this?

Hi Robbo,

if you’re going to change your thermostat and your car is still on warranty, I would have the dealer do it. I’m going to do it myself, but that’s because I don’t trust dealerswith other than the mosta basic things.
Choose an 82 DegC one (part of the 190 mod) by the way (although it’s winter now).

Something happened to me some time ago (as some people have hinted). My front grille got plugged with leaves and that made my temp shoot high: 123 DegC.
I didn’t get a HGF because I never stopped the engine, rather coasting down to a halt, taking the leaves out and letting the car cool naturally at idle.
Hope you did the same, the engine seems to be able to take it.

I went out for a drive yesterday in the snow (and although my curent problem is that my engine runs too cool), upon parking, I saw lots of snow and ice covering the fron tof the car.
Could that have happened to you and bocked your grille? then suddenly it melted unblocking it? That would be an explanation.

On the other hand, it is the general consensus is my thermostat has just broken, but that by default (closed) it takes the long routh through the radiator. It seems that when it opens, the water takes a detour through the heater.
I’m not so sure of this, and it’s not very well explained in the manual.

To say that it seems you can’t really overheat the engine due to thermostat failure, but overcool it.

So, was there ice in the front?

Thanks guys,

Uldis, When I looked at the temp, the first thing I thought of was when you had the problem with the leaves block up the grille. I was about to pull over and check when all of a sudden the temp decreased suddenly as I mentioned above so I just coasted home which was about a mile away.

When I got home, the first thing I checked was to see if the grille was blocked but it wasn�t! By this time the temp was at about 82degrees and car seemed to be back to normal.

I don�t think there was any ice either, the snow started just after I got home when I was on the drive trying to find the cause� Getting wet as usual!!!

Am I right in saying though that if the thermostat stuck shut, no �cooled� water would get through the cylinder head to the opposite end where the temperature sensor is and hence causing the increase in temperature.

Then when the pressure built up and it finally opened, the water was pushed through causing the sudden drop in temperature and then as it got back to normal the slight rise in temperature immediately afterwards.

Would the pressure also have caused the water to be forced out of the header tank?

I would get the dealer to do it (Although their not a Lotus dealer) but it�s a fair hassle to get there and sort out when it�s a easy enough job to do myself. Especially when every time I seem to take a car anywhere to have work done, I end up taking it back for a second time for them to fix things they didn�t do right the first time!
I always think if you want something done right, do it yourself!

Unless it is HGF and then I�ll be waiting for them on the forecourt.

Its already got the 82degree stat in at the moment, I know their only about �9 from Eliseparts does anybody know if you can get them locally from a Rover dealer?

Thanks again, Paul

Hmm, so it was no ice.

I would say that if it’s no HGF, then there can only be one thing, malfunction of the thermostat.
I can’t say for sure if the default is open or closed, but it could have staid in one position and then moved to the other.
And yes, I understand your frustration with the dealers, and if you try to change something simple you would invalidate the warranty. Best for them to do it then.

And yes, I was told the 82 DegC is available from Rover as well.

Hope you get it sorted.



There has been a lot written about thermostats on the Elise BBS - basically about how crap a lot of them are - naming no names … but I would source it from a dealer if I were you to be sure ( as you can be ) of getting one that opens correctly …

Just as an aside a friend of mine had a stat replaced in her VW, 2 days later it overheated - yep the (cheap) stat had failed …

Im alive… Just!

Christmas do was pretty good last night, my head feels a bit

Checked the water level this morning but its only gone down slightly and the oil still resembled Mobil 1 ms and not the Hellmans variety. Phew

It was dark though so I’ll check properly in the morning.

Tried to find a 82degrees thermostat, Whales only get them in on special order, Havent tried Mattys yet, will phone later.

Does anyone have the part number.

Just noticed, 1 more post and Im a member… YIPPEE


Robbo, My mate works for prodrive and they did the development work for the MGTF engine, as a result I have the build manual, it explains how the cooling system works, thermostat and all that jazz, I imagine it is the same as our system. Copied the page into Microsoft word and sent you a mail. Hope it is of some use, even if just for info

Thanks Rich_O


It has a section for 3 different thermostats but don’t know which one is the 82degree one, and it gives service repair numbers, whether this is new or as it suggests repair I am not sure. I will give my mate a call and see if he knows.




Ive just found the Lotus part number in the Archives

Lotus Part Number : A340K6007S

Dont know whether this number has any relavance to the Rover part number though.

Does anybody know

I believe the 82 thermostat part number (Lotus) for the 340R is A340K6007S. Presumably it’s the same thermostat as used in the Exige