Now i've only just noticed this,

But normally, when warmed up, my engine temp sits bang on 90. Never usually drops, and i dont think i've seen it go above that either.

But the past few days, it's been dropping quite low, 70 and below.

Now, a few factors, it's been about 8degrees outside as apposed to the normal 16/17.

And i've had the heater on a fair bit.

I'm not overly worried, as at least its not overheating.

When the temp is down, i'm still getting plenty hot air etc aswell.

Car is an Mk1 Octy Vrs.

Anything i should be worried about ?

Provided the car has been driven far enough, ie; 5 miles +, it should still be getting up to normal operating temperature. (mine always does).

I've not had any problems, but from what I've read on here the most likely/common culprit is the temp sender unit. (easy to get to and replace).

If not the sender unit then the thermostat may be broken or jammed open. (not so easy to get to and replace on a 18T).

bill

Since you're getting plenty of hot air (and as quick as usual, I guess) it's probably not a broken or jammed thermostat. On my prevoious car (Nissan) the thermostat broke now and then and (apart from the temp meter) it always resulted in poor heating when driving on main roads (less noticeable in city traffic). So I would start with the sender unit.

Mines never moved from 90 whatever the weather, sounds like as mentioned the thermostat could be jammed open?

Thanks guys.

I should've added, it will go to 90 still, but wont stay there.

I'm still thinking sender unit, or thermostat. The 3rd possibility would be that the fan thermoswitch has failed, and is running the fans when they're not needed.

Ken,

A valid point that ! Didn't think to check if the fans were running when the temp is low.

Will make a point of stopping and checking when the temp goes down next.

Thanks for that.

Sender unit - my temp fluctuated slightly - up and down - always below 90.

New sender about £30 - took me 10 minutes to replace - now 90 - rock solid.

Ken,

A valid point that ! Didn't think to check if the fans were running when the temp is low.

Will make a point of stopping and checking when the temp goes down next.

Thanks for that.

Johnny, it wont be the fans

Only the thermostat controls the minimum engine coolant temperature and the cooling fans do the exact opposite, control the maximum coolant system temperature.

Therfore even if the fans were running permanantly they could not reduce the engine minimun coolant temp to below 87 degrees C, because the thermostat would simply close and stop the flow of coolant to the radiator and maintain normal engine operating temperature.

Check the wiring to the temp sender and the plug connector, if OK, my money would still be on a faulty sender unit (which you can check resistance of if you have a suitable meter).

Hope you get it sorted

bill

Its the thermostat, yours will be stuck open. Really easy to do and the thermostat is also cheap.

The heater air will still be hot, because the water is still hot.

My mondeo thermostat was stuck open for ages and would only get to the normal point on the gauge when stuck in traffic, despite this the heater worked perfectly. Changed the thermostat, and problem gone.

Johnny,

Sounds to me like thermostat, if it reaches 90 when in slow or stationary traffic only to go back down again once you pick speed up. Faulty thermostats don't need to jam open, they can just partially open at a lower temp, so the radiator over cools the water (at normal motorway speeds, front-engined cars should get sufficient air flow over the engine so radiator cooling is minimal, hence if the thermostat is open the temp will sit well below its normal position). You will probably notice you are not getting quite the same fuel economy at the mo because of this.

However if you're going to do this as a DIY job, you need to drop the powersteering and (if fitted) aircon bits too.

So..Thermostat then !

Thanks for your help guys.

Lee, Fuel consumption has dropped over the past week or so, it's down to about 34mpg average, as apposed to my usual 39-40mpg.

I'll go order one.

Is it a pain to fit ?

I wish you'd mentioned the fuel consumption before. 110% certain it's the thermostat now!

I wish you'd mentioned the fuel consumption before. 110% certain it's the thermostat now!

Johnny

A faulty temperature sender unit could also increase fuel consumption.

I think the MK1 octy vRS is fitted with the Bosch Motronic engine management system, which also uses the signal from the engine coolant temperature sender unit to adjust the fuel mixture, timing etc.

bill

Ken,

I never thought about the fuel consumption to be honest, as i'd been in a lot of traffic recently, so presumed it had dropped due to that.

I'll go order one.

Is it a pain to fit ?

Probably, ask Lummox for the complete lowdown though.

I replaced the one in my 2.0L Corrado and for this I had to do move the powersteering pump out the way. You'll need to do this for the Octy engine too and the aircon pump (compressor or whatever its called). If your mechanically confident then yes, I'm sure it's more than do-able, but it won't be a 20 minute job I warn you now!!

Hang on, why have a few people said its really easy?

Hmm...

I'm not mechanically minded.

Any ideas on labour involved ?

On my vrs the sender would not rise above normal temp but it would intermittently drop then go back up to normal again.

Are the fans coming on ok?

Also Jonny when did you last have the timing belt/water pump replaced (mileage/age)?

I'd need to check on the water pump/belt, but the previous owner had it done at Jabba just over a year ago.

As for the fans, it's never gotten hot enough for them to kick in, the temp just drops when i start to gain speed and some more air gets in.

As previously mentioned thermostat sounds probable cause as temp senders are usually quite intermittent when they fail, normal one min nothing the next.But not always.