new thermostat lazy?

[robin]

Suspect stat
Pan
Hob
Cold Water
Thermometer

I'll leave the rest to you...

There is no doubt that the stat is opening; the question is whether it's opening under pressure from the water pump I think ...

cheers,
Robin

[steve_weegie]

Right, i've had the thinking cap on for a bit... I'm convinced its the spring opening - the resulting increase in water pressure due to pump RPM's correlates too directly with the drop in temperatureure to be anything else IMHO. The cold water from the rad can only come from one place :- the radiator side of the stat.

I'm going to poke it with VXJON's OBD scanner at the weekend and test like follows:

Get engine up to 60C so the stat is closed, but the engine loop and heater loop have warmish water in there
Rev to 4000RPM
Watch head outlet temperature on the OBD scanner. If it drops a lot, then the stone cold water from the rad must be forcing the spring open on what would be a fully closed stat.

I expect the temp to drop.... Now I ask myself why?

1. As the output from the heater loop connects to the engine side of the stat, low flow through here is causing a big enough pressure differential to open the spring?

2. The spring on the stat is gubbed?

3. Its possesed by something unholy?

Is option 1 a possibility even? I've looked at the cooling system schematics and think it might be
It would be nice to rule out option 3 too. Any religious types here that would be prepared to bless my expansion tank?

Cheers,

Steve

[RDH]

Right, i've had the thinking cap on for a bit... I'm convinced its the spring opening - the resulting increase in water pressure due to pump RPM's correlates too directly with the drop in temperatureure to be anything else IMHO. The cold water from the rad can only come from one place :- the radiator side of the stat.

I'm going to poke it with VXJON's OBD scanner at the weekend and test like follows:

Get engine up to 60C so the stat is closed, but the engine loop and heater loop have warmish water in there
Rev to 4000RPM
Watch head outlet temperature on the OBD scanner. If it drops a lot, then the stone cold water from the rad must be forcing the spring open on what would be a fully closed stat.

I expect the temp to drop.... Now I ask myself why?

1. As the output from the heater loop connects to the engine side of the stat, low flow through here is causing a big enough pressure differential to open the spring?

2. The spring on the stat is gubbed?

3. Its possesed by something unholy?

Is option 1 a possibility even? I've looked at the cooling system schematics and think it might be
It would be nice to rule out option 3 too. Any religious types here that would be prepared to bless my expansion tank?

Cheers,

Steve

Looks like you might need The Father, Son and Holy Ghost to help solve this one........

Or Robin?

[robin]

If the stat was in back to front .... no, don't even think about that

Two options: (1) The stat is opening below the correct operating temperature for some reason (2) the ECU and dash are getting duff info from the temperature sensor.


(1) The stat is opening.

The stat only opens for one proper reason - the temperature of the coolant in the bypass circuit is beyond the stat opening point.

A lazy stat will also open when the water pressure forces the stat open (fail safe design I assume).

(2) The temperature sensor is gash.


You can check (2) by correlating readings from your IR thermometer or similar at the water elbow with what it says on the dash, including the high RPM case.

You can check (1) by measuring the temp of the bypass circuit, just where it joins the stat housing (or nearby upstream if you cannot get a good bead on the stat housing).

If (2) and (1) check out OK and your engine does not overheat when running down the motorway on full throttle for a while, then you *must* have a faulty/lazy/missing/badly fitted stat.

Cheers,
Robin

[steve_weegie]

Ok, update time... Posted a thread on seloc and it seems a few people have got the same issue at the moment, all with new 82c stats. Geary is getting one pressure tested and sent up for me to fit and post results on.

Cheers,

Steve

[robin]

Ok, update time... Posted a thread on seloc and it seems a few people have got the same issue at the moment, all with new 82c stats. Geary is getting one pressure tested and sent up for me to fit and post results on.

Cheers,

Steve

If you're going to take it all to bits again, why not put in the OE stat?

Cheers,
Robin

[fd]

If you're going to take it all to bits again, why not put in the OE stat?

DING !

First sensible suggestion award of the thread to Dr Iddon . . .

You have A thermostat, but not the CORRECT thermostat . . .

The Stat is not the correct one for the installation . . . you have problems . . . do you need any more clues as to why that may be . . . it ain't 'lazy' . . . it's just not the correct part . . . it's entirely possible that the spring rate specified on this incorrect part is . . . eh . . . incorrect . . . for example . . .

Get a standard one from Rover . . .

Fd

[campbell]

Steve,

Was there a particular reason you picked an 82 deg stat, or was it a case of whatever was available in a hurry etc?

What is the "standard" stat rating...92 deg?

Campbell

[steve_weegie]

Well, having seen where the thermostat was when diagnosing my head gasket problems, i opted to do the sensible thing and change it while it was accessible. After all, its 6 years old now. The 82c one was chosen as I've seen temperatures that are too high for my liking while on track. Dropping the inlet water temp by 6c will mean that the head runs quite a bit cooler - not so much of a concern while there's plenty airflow over the radiator, but taking heat out of the head while lapping will mean less heat to soak into the cooling system while in the pits.

Rover didnt do an 82c one, and i've never had a problem with anything i've had from eliseparts in the past, hence I went shopping there. Geary has informed me his stats are supplied my QH, and we all know that there are Q/C issues with their balljoints.... I suspect its just a case of bad luck again...

Campbell, the standard stat is 88C

Cheers,

Steve

[campbell]

Your rationale for changing it while the head enabled better access was very sound, as we discovered when doing my own head last year!

Can't comment on the 6 deg reduction in temps for trackdays etc, but as a fairly non-mechanical sort I can certainly follow your logic

[steve_weegie]

Yes, I'm NOT looking forward to changing it again! To be honest, if Geary wasnt pressure testing this stat before sending it up and I hadn't promised to fit it and post back to all the Seloc folk that are having the same problem, Ali from SLS informed me I can buy an 82c one directly from Lotus.... and I would!

Cheers,

Steve