Running hot

Steve61 · 12th September 2014, 10:35

My 2.5 V6 Connie is running seriously hot.
It's not losing water, but the temp gauge rises into the red within a couple of miles and sits there.

I tested the temp with the OBD and it rises rapidly to 123 degrees and then sits there, even though the fan is running.

The fan runs on for a good 20-30 seconds after parking up.

My mechanic says that the second speed has failed on the fan.
Is this a dead fan, or is it the resistor that has failed?

I'm guessing that it's a three speed if he says the scond speed has failed, nut it's a 52 plate, so I'm not 100% sure...

doopydug · 12th September 2014, 10:41

At that temp, your third speed would kick in and keep it cooler. Sounds like an airlock or a thermostat problem

stevestrat · 12th September 2014, 10:52

Tend to agree with Ian, airlock or thermostat, under normal running the fan shouldn't really come into the equation as there should be enough air flowing through the radiator to cool things better than that. I lost the low speed on my 2 speed fan and the diagnostic temp reading never got above high 90s in normal driving.

Mechanic reckons the fan second speed has failed . . . . what about the low speed, that should kick in long before the second speed is required and if it is a three speed fan it won't have a resistor.

Steve61 · 12th September 2014, 10:55

I'm not 100% certain if it is a 3 speed..
I'm just letting it cool down properly to try the Demister test again.

stevestrat · 12th September 2014, 11:02

Have a look at this, covers fan testing methods, demister and trinary switch although if doing the trinary switch test contrary to what Jules wrote I found the engine had to be running.

Steve61 · 12th September 2014, 12:58

Well,
This is getting worse by the minute.
Started the car up and let it idle, it ran up to 105 degrees and no fan came on at all.
Later, after it had cooled back down, I thought I would take the cap off the header tank just for a quick look.
Almost a pint of water was forced out as I undid it.

Gotta admit that i don't know what I'm looking at now....

SD1too · 12th September 2014, 13:25

O.K. Steve, first of all NEVER remove the expansion tank cap when the engine is hot. You were lucky not to scald yourself.

Now, stand at the radiator grille and peer in towards the fan. You'll see the fan blades and the black plastic surround. On this surround, at the two o'clock position, can you see a silver rectangular component with a wire at each end? Please report back: yes or no.

Secondly, you have definitely lost your slow fan speed. In addition I believe that your thermostat may be stuck shut. Only this could explain the rapid rise in temperature to the levels you describe. Another club member had the same problem recently, and I was able to help diagnose it. The evidence you gave about the fan running after the engine was stopped proves that your mechanic doesn't know how the 75/ZT system works.

Is the expansion tank cap on or off at the moment? If you can reply quickly I will talk you through what to do next.

Simon

Steve61 · 12th September 2014, 13:31

Hi Simon,
Just put the cap back on...
Looking through the fan I don't see a resistor.
The fan did cut in eventually, but not until around 120 degrees.

SD1too · 12th September 2014, 13:40

Right, thanks Steve.

Take the expansion tank cap off again and look inside for the tab marked 'MAX'. It's towards the bottom of the tank, but as you've lost a quantity of coolant I'm expecting it to be visible. If it is, top-up the coolant to that marker but no higher. Replace the cap.

Now locate the large diameter hose just to the left of the air cleaner. It's the hose with a plastic screw sealed into it. That's for bleeding the system; don't undo it! Once you've identified this hose, I'm going to ask you to start the engine and watch the temperature gauge closely. As soon as it reaches the "normal" position (nine o'clock) return to the engine compartment and grasp that hose in the palm of your hand. Is it hot or is it cold?

Please report back.

Simon

Steve61 · 12th September 2014, 14:11

Apologies Simon,
I'm doing this between work calls..
Assuming you are refering to the large diameter pipe running right to left (the only one I see with a bonded screw about half way along it - Radiator top hose?), that is very hot.

12th September 2014, 10:35	#1
Steve61 Avid contributor Rover 75 Connie Saloon Join Date: Feb 2014 Location: Greenwich Posts: 123 Thanks: 0 Thanked 23 Times in 9 Posts	Running hot My 2.5 V6 Connie is running seriously hot. It's not losing water, but the temp gauge rises into the red within a couple of miles and sits there. I tested the temp with the OBD and it rises rapidly to 123 degrees and then sits there, even though the fan is running. The fan runs on for a good 20-30 seconds after parking up. My mechanic says that the second speed has failed on the fan. Is this a dead fan, or is it the resistor that has failed? I'm guessing that it's a three speed if he says the scond speed has failed, nut it's a 52 plate, so I'm not 100% sure...

12th September 2014, 10:52	#3
stevestrat This is my second home ZT260 #243 (resting) Join Date: May 2010 Location: Prestonpans Posts: 22,484 Thanks: 650 Thanked 4,624 Times in 3,358 Posts	Tend to agree with Ian, airlock or thermostat, under normal running the fan shouldn't really come into the equation as there should be enough air flowing through the radiator to cool things better than that. I lost the low speed on my 2 speed fan and the diagnostic temp reading never got above high 90s in normal driving. Mechanic reckons the fan second speed has failed . . . . what about the low speed, that should kick in long before the second speed is required and if it is a three speed fan it won't have a resistor. __________________ Steve T4 Location Map

12th September 2014, 11:02	#5
stevestrat This is my second home ZT260 #243 (resting) Join Date: May 2010 Location: Prestonpans Posts: 22,484 Thanks: 650 Thanked 4,624 Times in 3,358 Posts	Have a look at this, covers fan testing methods, demister and trinary switch although if doing the trinary switch test contrary to what Jules wrote I found the engine had to be running. __________________ Steve T4 Location Map

12th September 2014, 13:25	#7
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,382 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	O.K. Steve, first of all NEVER remove the expansion tank cap when the engine is hot. You were lucky not to scald yourself. Now, stand at the radiator grille and peer in towards the fan. You'll see the fan blades and the black plastic surround. On this surround, at the two o'clock position, can you see a silver rectangular component with a wire at each end? Please report back: yes or no. Secondly, you have definitely lost your slow fan speed. In addition I believe that your thermostat may be stuck shut. Only this could explain the rapid rise in temperature to the levels you describe. Another club member had the same problem recently, and I was able to help diagnose it. The evidence you gave about the fan running after the engine was stopped proves that your mechanic doesn't know how the 75/ZT system works. Is the expansion tank cap on or off at the moment? If you can reply quickly I will talk you through what to do next. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce. Last edited by SD1too; 12th September 2014 at 13:43..

12th September 2014, 13:40	#9
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,382 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Right, thanks Steve. Take the expansion tank cap off again and look inside for the tab marked 'MAX'. It's towards the bottom of the tank, but as you've lost a quantity of coolant I'm expecting it to be visible. If it is, top-up the coolant to that marker but no higher. Replace the cap. Now locate the large diameter hose just to the left of the air cleaner. It's the hose with a plastic screw sealed into it. That's for bleeding the system; don't undo it! Once you've identified this hose, I'm going to ask you to start the engine and watch the temperature gauge closely. As soon as it reaches the "normal" position (nine o'clock) return to the engine compartment and grasp that hose in the palm of your hand. Is it hot or is it cold? Please report back. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

12th September 2014, 10:41	#2
doopydug Posted a thing or two Rover 75 Saloon Join Date: Nov 2013 Location: Fife Posts: 1,595 Thanks: 88 Thanked 269 Times in 235 Posts	At that temp, your third speed would kick in and keep it cooler. Sounds like an airlock or a thermostat problem

12th September 2014, 10:55	#4
Steve61 Avid contributor Rover 75 Connie Saloon Join Date: Feb 2014 Location: Greenwich Posts: 123 Thanks: 0 Thanked 23 Times in 9 Posts	I'm not 100% certain if it is a 3 speed.. I'm just letting it cool down properly to try the Demister test again.

12th September 2014, 12:58	#6
Steve61 Avid contributor Rover 75 Connie Saloon Join Date: Feb 2014 Location: Greenwich Posts: 123 Thanks: 0 Thanked 23 Times in 9 Posts	Well, This is getting worse by the minute. Started the car up and let it idle, it ran up to 105 degrees and no fan came on at all. Later, after it had cooled back down, I thought I would take the cap off the header tank just for a quick look. Almost a pint of water was forced out as I undid it. Gotta admit that i don't know what I'm looking at now....

12th September 2014, 13:31	#8
Steve61 Avid contributor Rover 75 Connie Saloon Join Date: Feb 2014 Location: Greenwich Posts: 123 Thanks: 0 Thanked 23 Times in 9 Posts	Hi Simon, Just put the cap back on... Looking through the fan I don't see a resistor. The fan did cut in eventually, but not until around 120 degrees.

12th September 2014, 14:11	#10
Steve61 Avid contributor Rover 75 Connie Saloon Join Date: Feb 2014 Location: Greenwich Posts: 123 Thanks: 0 Thanked 23 Times in 9 Posts	Apologies Simon, I'm doing this between work calls.. Assuming you are refering to the large diameter pipe running right to left (the only one I see with a bonded screw about half way along it - Radiator top hose?), that is very hot.