Temperature goes sky high

[DEL VR6 0]

Havent had this problem before. The needle on the far left of the instrument goes very very high, and after a while the red temperature light comes flashing on.

 

When i opened the bonnet, both fans were working (at a very high speed) I dont get it. What is overheating? Is it the water, or the oil? There is no steam or anything like that... what should i do / check?

[saysomestuff 0]

Sounds like thermostat to me.

 

Check the level of the coolant in the header tank (Black cap DO NOT open when the car has been running!!) as the temp light flashes when the coolant level is low, if it's empty you either have a leak or a blockage (if system is blocked pressure builds up and steam escapes from header cap).

 

if you find a leak, fix it. If not:

 

Seeing as we know the fans are working it not them, when you have run the car for a bit and the temp has gone up, check the temperature of the two big pipes connecting to the left of the radiator.

 

If top one is hot and rock solid and bottom one is cold - you have a blockage in the coolant system which is likely to be a failed thermostat or blocked radiator.

 

Let us know more symptoms when you've checked these

[DEL VR6 0]

Right, having consulted the instruction manual, this is the coolant temperature. and it has been very high. there seems to be plenty of liquid in the round expansion tank. i dont get it. fans are working, and there is lots of liquid in the system. therefore, its not all leaked and pissed away, and neither is it cos the fans dont come on. Could it be cos the concentration should have more "coolant" and less water content? Im stuck!

[saysomestuff 0]

when you have run the car for a bit and the temp has gone up, check the temperature of the two big pipes connecting to the left of the radiator.

 

If top one is hot and rock solid and bottom one is cold - you have a blockage in the coolant system which is likely to be a failed thermostat or blocked radiator.

 

Try this ^^

[Baz2004 0]

Could try and add more concentration of coolant but if it wasn’t causing trouble before (coolant was added) then I don’t think this will solve things.

 

You may need to check your water pipes for blockages and your stat and water pump impeller.

[DEL VR6 0]

yep, i think on the way home tonight, thats what i will do. Just hope i dont have a crap journey with lots of traffic and all that crap you dont need when your car aint behaving as it should! Cheers for the advice 'saysomestuff'.

[DEL VR6 0]

well, as i rememeber, a few months back, the light used to flash but the temperature was fine. At that time, i remember the bowl shaped tank looked very low, so i topped it up using just water. This stopped the light flashing completely. Its only now that the temp is going way too high, and then the light begins to flash. *del scratches his head*

[Kevin Bacon 5]

What is the oil temp like when this happens?

 

The VR should very rarely use the 2nd speed on the fans....mine has once in 2 years, and that includes lots of heavy traffic stop-start driving....so something is amiss. I'm going to go with my instincts and suggest a knackered thermostat, so do as SSS says and check the rad hoses.

 

And get it sorted ASAP as the VR6 is intolerant of extended hot running....it'll blow the head gasket.

[saysomestuff 0]

Just hope i dont have a crap journey with lots of traffic and all that crap you dont need when your car aint behaving as it should!

 

you're telling me - my thermostat stuck closed and the heater matrix blew up on the edgware road filling the car with steam! So take it steady

 

Cheers for the advice 'saysomestuff'.

 

No worries

 

Oh and although it's documented that the light flashes when temp is high it also flashes when level is low, trust me

[DEL VR6 0]

by the way, its SODDING TYPICAL that the day i get my repaired Borbet Alloy wheels back from being repaired, that this happens! Oh well, at least i will be sitting in traffic, overheating and $hitting in my pants staring at the temperature gauge with nice 16 inch alloys back on!

[DEL VR6 0]

Ok folks, i have checked both of those hoses that are at the side of the radiator, and they are both pretty much hot. Whats the next step?

[dr_mat 0]

That was obvious - the fan temp sensor is in the rad, so the fans wouldn't be on at ALL if the radiator was cold.

The most likely explanation seems to be air locks, induced by a leak somewhere. Prime candidate is the hose that goes from the heater matrix to the back of the cylinder head...

I'd get the coolant checked for oil or exhaust gas contamination too..

[DEL VR6 0]

Would it be worth running the enging with the cap off the water coolant tank to let any air bubbles bleed themselves out of the system? I remember my mechanic doing that once with a jug of water in his hand, topping it up at the same time. Cant remember the exact process and whether the engine was hot or cold ot the time.

[Roger Blassberg 0]

If they are both hot, i.e. there is little temperature difference between them, it sounds to me as though your radiator isn't doing much radiating despite there being a flow through it.

 

I would suggest reverse flushing it as the next step.

 

Have you, by any chance, mixed different types of anti-freeze together - G11 and G12 don't like each other and form a gooey mess which clogs up the water ways. Give it a really thorough flushing out with a hose pipe, then refill with the correct concentration of G12+

 

Best wishes

 

RB

[DEL VR6 0]

i think there is no antifreeze in there. A few months ago the tank was empty and the light started flashing so i topped it up with H2O and it had been fine until now. So im guessing that only water is circulating around the system. Im still puzzled where the water went that time, as there doesnt seem to be any leaks.

[dr_mat 0]

"There doesn't seem to be any leaks."

 

Classic. There was another thread recently where someone had eratic temps and it turned out to be a blown hose (though of course it only blows when up to temperature, AND the location of the break is under the plastic engine cover near the throttle body so you can't actually see it).

 

Which we tried to tell him for days and days until he finally changed it and ... problem solved..

[DEL VR6 0]

I hear you Dr Mat. I had this leak a while back. the hose under the plastic cover, and it goes all over the hot parts of the engine making the car look like theres something funky going on under the hood... I only say that this time round there dont seem to be any leaks as the water bottle level has been constant, and parked the car on a dry garage floor and there hasnt been any water underneath after.

 

What do you think to the idea of running the enging with the lid off the water bottle?

[Reggit 0]

This could be a knackered temperature sender(yellow one), it happened to me once. Gives a false reading at the gauge.

 

It would also be a good idea to put a new 'stat in as a matter of course.

[dr_mat 0]

That would imply that both the temperature sender for the dash gauge AND the fan thermo switch were faulty.. in the same way ...

Unlikely, but not impossible.

[Reggit 0]

Yellow sensor also controls the fans turning on iirc, so could in theory give an erronious signal to both the temp gauge and fans.

 

It happened to me, and is an easy/cheap job, so no great loss if this doesn't fix it.

 

Just my 2p

[Kevin Bacon 5]

Aye, the yellow one is the same sensor but with siamised connections....so it's very possible to lose the fan speed and temp guage at the same time.

[Funkster 0]

Yellow sensor (now black/blue) does the run-on fans, not the fans while the ignition is on. Also, it costs 26 quid from the stealer...

 

fwiw.

--

Olly

[Roger Blassberg 0]

but wouldn't the thermoswitch in the radiator have to close too to set the fans a-running whilst ignition is on. I thought that the yellow sensor only controlled the fan run-on, ie after switching off the engine.

 

Best wishes

 

RB

[Roger Blassberg 0]

Bu@@er !! Beaten to it !!

 

Best wishes

 

RB

[Kevin Bacon 5]

Sorry, yeah I meant the after run/burner/birth circuit.....

 

But with the ignition off and the after burner running....the rad switch still governs the speed. So the yellow or whatever colour it is, is essentially just a switch for the Aux pump to run autonomously.