2.5V6 coolant and fan woes
 

Exactly a year ago my engine overheat light came on whilst going up the motorway and I discovered a substantial loss of coolant, traced to a faulty three year old) thermostat. I had that replaced, and had a low speed fan Jules gold resistor at the same time as the low speed resistor was caput.

Some months later a new coolant loss. Eventually we tracked down that the water pump had a slow leak. Given that the cambelts were due the end of this year I brought that forward and had new belts and pump fitted last month. For a few days following I checked the coolant levels and all seemed fine so I stopped the daily checks.

Until yesterday when the red overheat light came on again. I topped up the engine with a litre of coolant once it had cooled down, which seemed to be enough to take it to the maximum setting in the filler expansion tank. But a few hours and fifteen miles later I checked and the level had dropped right down - I ended up putting a further litre in.

I had the car examined thoroughly today but we couldn't find a trace of a leak anywhere. No coolant in the "V", nothing under the new water pump. The rubber pipes weren't corroded (so unlikely to be oil cooler) and there was no emulsion or mayo in the header (so not head gasket I hope). Oh, and I have a new coolant filler cap as the previous one did have an issue with the O rings, so hard to see how coolant could be escaping through it.

The only thing we did find, on T4-ing the car, was that we couldn't activate the low speed fan, and that the middle and high speed tests sounded exactly the same. I only have a two speed fan so I don't know if it is supposed to do nothing on the low speed T4 test, but surely there should have been some difference in sound between medium and high speed? Could the control or the resistor be faulty? On letting the car idle, the fan kicked in at high speed at 101 degrees. Normal temperature (after topping up yesterday) is around 93 degrees, rising to no more than 101 when idling at traffic lights.

So it seems I have a leak somewhere, and a fan problem. But I'm lost as to the source of the leak, and the nature of the fan problem. I could jhust keep topping up with coolant, but that doesn't really solve the problem, so I would welcome any suggestions for what to look for next, as I need a reliable car for work and can't afford for the Rover to break down or to be off the road any length of time.

Hi David.
Who did the T4 session for you, as they should know that a two speed fan with gold resistor will not have a medium speed only low and high speed, also for the fan to kick in at 101 I would imagine that is the low speed.

you have said above that you managed to obtain two speeds from the fan if so then the fan is ok, it would have been low & high. :shrug:

Note the speeds of the four wire 3 speed fan below in this video, and try to remember how yours sounded.

https://youtu.be/t0Y70yxz45I

Hi Arctic,

I spent a couple of hours with Terry (TS) yesterday and between us we couldn't figure out what was going on hence the original post. Yes a two speed fan won't have a medium speed - but the T4 triggered the fan to come on on the medium and high settings, not the low setting. Does that mean the low speed isn't working? But hang on, the medium and high sounded equally loud/fast, implying there is only one functioning speed. But in that case why does the fan come on at 101 degrees? None of that makes much sense.

As for the leak, we are flumuxed as there is no obvious source for the 2 litres that I've put in over the past few days to have escaped from. And I'm not happy with the idea of driving the car until something big goes wrong, I'd rather fix the problem now - except we can't work out what it is!

My only thought was whether insufficient coolant was added after the change of cambelt and water pump last month, but with a bubble or something to cause the header tank to look full for the first few days. But if so, why would the car have waited until now to overheat? And that doesn't explain what's going on with the fan, unless that's happened since the car was serviced when the belts were done. So none the wiser (yet) - and I don't want to take it to my local garage as I'm sure they will assume it's HGF and tell me to fit a new engine or scrap the car!

That's a lot of coolant to account for. It could be leaking into the oil without any oil getting into the coolant. Have you checked the oil level? If two litres went into the sump, the dipstick would make it pretty obvious.

The V6 fan should trip on at the lower/lowest speed at around 100C and that's what happened. Whatever the T4 seemed to tell you, have you tried the simple Demist test? The Demist test is definitive. If the fan starts with the aircon system and runs continuously, then the lower speed is OK.

All this is assuming the fan system is the standard 2-speed type and hasn't been modified in some way. The T4 results seem ambiguous.

TC

A 2002 model ZT would have a 3 speed fan without a resistor from the factory, so it has already been modified?

With the KV6 it could well have an airlock as most mechanics don't bleed them properly, though if Terry has fitted the belts and the waterpump it should be done correctly?

Tom.

Hi David
As stated above if Terry as looked at it then you have one the best guys whom knows his way round these cars.

As the fan been checked to see if it as a silver or gold resistor fitted by visually looking through the front grill at about 14.00 hours.

Because as Tom as suggested it sounds like that a three speed fan is fitted and may have been tampered with ? sounds like the medium speed is kicking in for the low speed, best to do as TC says and check the demist test out, start engine make sure all the A/C is off press demist button only and check through the front grill that the fan is running continuously.

If not then the low speed as failed, or the silver resistor as failed if it is a 2 speed fan.

With the coolant having to be added and no leak found I would be inclined to re-bleed the system making sure the header tank is raised as I high as possible while doing so then get back to us.

OK, so I just checked oil and level seems fine. In any case it was only changed when the belts were done a month ago (note, not by Terry as he is planning to retire soon and no longer does belts).

Terry upgraaded the original fan to a two speed fan pack nearly five years ago when I first had him look over the car after buying it. Just last year he fitted a "Jules" replacement gold resistor to restore the first speed.

All is well with the triggers for 1st and 2nd speeds just that the speeds have no distinction between 1 and 2 speedwise. To be fair, Terry wondered if this might be down to the fact that T4 is only pulsing the speed for a short period so may not have time to ramp up to the 2nd trigger speed in time before cutting the pulse.

Having driven only 20 miles home on Friday after seeing Terry I waited until last night before checking coolant to be sure the engine was totally cold. On releasing the filler cap there was a feint hissing sound and the header was dry. I had to add maybe 150mls to get it back to max level again. So it's still going somewhere.

At the last service I had a new (well, purloined but in good nick) cap fitted in case the existing one was leaking slightly. So hope we can tick that off too. Still mystified about the slow coolant loss.

What did your Demist test show?
The Demist test will definitely trip the lower speed. This must be slower than the high speed because the resistor is in series with the motor. If this test shows no difference between high and low speed, then the wiring is non-standard or the resistor has short circuited somehow.

TC

Sorry for delay in responding - when I put the demist on (with aircon/climate control switched off) the rather loud engine fan came on straight away.

The faint hiss is water having been lost, and a small vacuum having been created. You are loosing water!
pump, radiator, hoses, oil cooler, inlet manifold gaskets, thermostat, bleed screw, expansion box, even change the new cap!. Notice the similarities with recent posts. http://www.the75andztclub.co.uk/foru...d.php?t=251095
All the discussions about the fan is irrelevant, as long as it just does come on.