Rad fan won't test - Toaf

[vitesse]

Went to view a spares or repair V6 today - overheating venting coolant, garage diagnosed heat gasket, new thermostat, new rad. Analogue temp gauge read mid-way, yet self test (7.1) only 10 degs (input from same sensor?) - radiator fan didn’t move. Tried testing fan with Toaf, nothing on any speed even with slider mid-way, but demist test does operate the fan. Too cold at minus 5 to test further, plus a weak battery, but must be worth a few bob at least. Ideas please?

[T-Cut]

I'd suggest you forget TOAF at this stage. The problems you note are standard issues that should be easy to diagnose.

The temperature gauge and the diagnostic routine do indeed use the same signal from the head sensor. However, Test 7.1 gives the ambient temperature not the coolant temperature, so maybe explains the difference? You need 7.0 for the engine temperature.

The demist test suggests radiator fan is OK. Did it run continuously until demist was disabled? A pulsing fan is a fail. The fan won't trip on to cool a hot engine until it reaches 100C or so. With an ambient of -5C, did it get anywhere near that?

As a starter, check for coolant leakage from the thermostat area. It's the weakest part of the system. Consider a top up/bleed. How long does the engine run before the coolant is ejected? On the face of it, it seems like one sick engine at this stage, but you need to confirm it yourself. I'm sure you'll get lots of advice here.

TC

[SD1too]

Hi Mike,

Just to add a few more thoughts to T-Cut's excellent first response:

• Garage diagnoses head gasket? Well, they would, wouldn't they! Are there any other signs e.g. mayonnaise?
• You say "overheating". I don't see any evidence of that in your account.
• "New thermostat, new rad": was the cooling system refilled and bled properly afterwards? If not, there could be an air lock.
• Has anyone put K-seal into it?

Originally Posted by vitesse

... must be worth a few bob at least. Ideas please?

I'd go back, start it and monitor the coolant temperature using IPK diagnostics 7.0 to see if it really does overheat and at what temperature the coolant ejection takes place.
Always remember that a head gasket failure on a KV6 is very unlikely.

Simon

[vitesse]

Thanks both for your replies. Not sure now if I got the test number wrong or what as the ambient temperature was probably much lower, not even plus. The cooling fan ran all the time while demist was selected, no pulsing. No knowledge of Rad weld or similar.

That the car has overheated is without doubt according to the owner plus there’s physical evidence of overflow around the expansion tank.

The car was running for about 10 minutes, and the analogue gauge, which I know is unreliable, gradually moved to its 9 o’clock position. No coolant lost during this time, but that might be because of the low outside temperature.

Knowing the V6 quite well and now having heard that a sniff test was negative, I’ve put in a bid. If accepted, the plan now is to move it from the garage and perform further tests at home, including bleeding the system. I intend to drive it home running demist continuously, and with the onboard system active.

But still baffled why Toaf doesn’t activate the fan. I’ve tested literally dozens of 75s at local meets using Toaf and never come across a case where the demist test works but Toaf doesn’t. Suspect that the ECU isn’t supplying the necessary trigger(s) for the fan.

Thanks again - more to follow.

[roverbarmy]

Overfilling of the header tank leads to coolant ejection due to the normal expansion. This is often mistaken for overheating by folks who do not know that the "max" level is at the bottom of the view you have of the header tank. The header tanks are therefore often overfilled when being "topped up" and continue to eject coolant on a normal warm up.A bad header tank cap or O rings can also lead to coolant loss on warm up.

[vitesse]

Thanks for the reply, the car was not overfilled and it was too cold to explore / bleed away from home but after two attempts (overheated) and a final tow the car is now home. Incredible that the thing can overheat when it is 12c below! No heat from the heater suggests an air lock, something I’ll have a look at tomorrow.

Regards

[SD1too]

Originally Posted by vitesse

Incredible that the thing can overheat when it is 12c below!

I do know of one KV6 whose thermostat didn't open which resulted in rapid overheating. What temperature did your car reach and how quickly from a cold start? Did the fan run?

Simon

[vitesse]

Simon.

Don’t know what the final reading was, I’d looked briefly before and noticed 112 and then suddenly the analogue gauge flew up and engine overheating message appeared on the message centre. At the time I was driving an igloo on wheels as there was no heat at all from the heater. The car had been running at idle for about 10 minutes before setting off.

I drove with the demist on as I knew this activated the fan. The thermostat and radiator were replaced sometime around June.

Just tried bleeding with the expansion tank raised to the limit, cap off, heater on full. No progress at first but switched engine off to refill coolant and there was a lovely gurgle, like a satisfying belch, switched back on and now there was heat from the vents. Took it up to 90c, top hose doesn’t seem filled or overly hot but it’s still minus 6 outside. A road test follows but got to put the friction tyres on first.

Mike

[vitesse]

After that satisfying belch matters seem to have improved considerably. Cabin heating is good and today after a good run at varying speed everything was normal. Running temperature around 93 - 95, and I found the rad fan working when I got home. Going to run Toaf again later, changing a few options and re-checking fan operation.

Thanks for the answers, I'm not yet saying I'm out of the woods as the woods are endless here.

Regards

[SD1too]

Originally Posted by vitesse

Running temperature around 93 - 95 ...

That's more like it!
Keep us informed please Mike.

Simon