Cooling fans running,temperature normal

[PTR200Jag]

I have noticed that BOTH the fans on the radiator are running when showing normal engine temperature on the dash gauge.

They do NOT run when engine first started and they do turn off a few seconds after the ignition is turned off.

I have also checked to see if they run with ignition on but no engine running... they do NOT, also they do not run even when the temperature is a third way up to normal on the temp dash gauge.

Can't remember to check when the gauge is any higher 'cos I am usually driving by then

They do NOT appear to be running flat out when the engine temperature is showing normal either.

The air con is turned OFF in all instances too...

Is this right or should I be looking for some trouble?

[mike020150]

The temp gauge is designed to remain in the normal zone except under the most extreme circumstances. Poor logic, I know but that's how Jaguar designed it; so using it to detect subtle temp changes is impossible. If the thermostat is newish and the car isn't using water, it's probably just paranoia setting in. Mike.

[PTR200Jag]

The temp gauge is designed to remain in the normal zone except under the most extreme circumstances. Poor logic, I know but that's how Jaguar designed it; so using it to detect subtle temp changes is impossible. If the thermostat is newish and the car isn't using water, it's probably just paranoia setting in. Mike.

Paranoia, paranoia, who told you that, come on, tell me, I have got to know, no, I have a right to know

So the first I will know about an overheat is when it, err, overheats?
Just didn't seem to be logical for the fans to be running when it shows normal temperature....

I wondered if the fans are controlled on engine speed / road speed so that at standstill they come on to make sure temperature stays down... but that would be to complicated for Jaguar if they can only build a hot/cold switch temperature gauge !!

Thanks for the reply, Mike appreciated.

[J44EAG]

I can only speak from a similar condition on my s-type V8 which is very similar in design to the XK8.

What happened to my car was a perceived overheat condition. Fans running all the time which was unusual, a full hot indicating temperature gauge and a reluctance to start when cold. Experience had taught me that the fans only ever cam on if the car was short of coolant.

The upshot of the issue was that I changed the £13 temperature sensor on the cylinder head manifold pipe. 19mm spanner screw out the sensor then screw in a new one. Instant success. Gauge back to normal, fans off and good starting again when cold.

I appreciate that you have some symptoms similar to those I experienced but not all. The temperature switch sensor if duff, certainly caused fan running on my car and disappeared when the sensor was replaced. Just a few ideas which I hope might be useful.

http://www.jec.org.uk/forums/viewtopic.php?f=201&t=6228

Mike K

[PTR200Jag]

Mike, that's quite an interesting point in that the temp sensor feeds its "heat" information to the ecu's and those in turn interpret that as a particular condition of the engine state and act accordingly.
I see you mention in the article the fact that there were some improvements in other running situations too and that you suggest it was linked to the water temperature sensor beginning to fail... Is it still running well now confirming that suspicion?

If I am beginning to experience a problem, the fans running, it hasn't shown up anywhere else yet and it would appear the temp on the engine is normal.... whatever that means !!

Still, worthwhile keeping an eye on it I think, so thanks for sharing !

[J44EAG]

No problems since.

This failure occurred in full view of most of the Co-ordinators and a diagnostic test confirmed an issue within the cable or the sensor. So I put the new sensor in and all went back to normal and the engine was sweeter than previously.. Prior to the total failure of the sensor, the car had been loosing its upper sharp edge. It blew a coil and the MAF sensor was also suspect.

I bought the MAF off a scrapper for a fiver and that helped a bit prior to the temperature sensor quitting. I believe The XK8 MAF is the same as an S-type unit but please check. That opens out possibilities at the breakers. Otherwise they are around £89 new. They need to be cleaned of crank case breather sludge. Clean the hot wire with spray switch cleaner. Don`t touch the hot wire for fear of damage. Renewing the MAF perked things up but had nothing to do with the issue when the temp sensor failed. Neither did the blown coil. Coil and MAF obviously not related to the fan issue.

I`ve found V8 models usually need cooling system work by about 75k miles. New water pump with metal blades, new thermostat as a precautionary maintenance, the thermostat tower because it is plastic and a new serpentine belts. Nothing lasts for ever and if one item collapses it impinges on several other items in the same network.

Mike K

[PTR200Jag]

That's encouraging, just to note that one sensor can screw things up completely ! and then it be an easy fix !

Here is a bit on info I was sent by a friend re the fans on XK8... from Jaguar tech paper I think.

Two electric fans are installed in a plastic cowl on the rear of the radiator. The fans are 12" and 12.8" diameter and are controlled by the ECM via the cooling fans control module. When the fans come on they operate in either slow (series electrical supply) or in fast (parallel electrical supply) mode.

Not sure if the wording is as Jaguar but the two interesting points are that the fans control module is in control probably using signals from all over the system but more importantly the last sentence is that there are two speed modes slow and fast.
My fans are on the "slow" mode I believe from the sound and the lazy way they seem to be turning so I am hoping all is ok !!

[PTR200Jag]

What happened to my car was a perceived overheat condition. Fans running all the time which was unusual, a full hot indicating temperature gauge and a reluctance to start when cold.

Experience had taught me that the fans only ever cam on if the car was short of coolant.

Mike K

The short of coolant comment made me check the header tank last weekend and it was below the neck by about 2", so topped it up to the neck level as per manual.

This week the cooling fans have not been on as much... if at all, each time I have got out after coming home there has been no sign of fan activity.
Just checked the header again today and its just on the neck......

However, I have just noted what looks to be coolant at the front of the engine sitting on the block to sump flange... very little but..............

[J44EAG]

I`ve had a few V8 leaks over the years.

The obvious one was a collapsed water pump front bearing on original factory fit unit. Well known leak malady and an easy fix. That issue is solved by fitting the later 4.2 water pump which also has the benefit of metal not plastic impeller.

This unit is distinguished by having two hex head bolts at the 10 and 4 o`clock position in addition to the drilled bolt holes in the pump itself. Loads on ebay for around £35 and not difficult to fit. Slip off the serpentine belt by placing a 3/8 socket driver on a torque wrench and insert into the square hole in the belt tensioner. Lever to the left whilst slipping the belt off the water pump pulley , centre top front of the engine. A pump change should take no more that 20 mins including gasket change.

Leaks down the front of the engine can be caused by defective seals inbetween the plastic manifold pipe flanges and the cylinder heads. That failure though is very rare.

The thermostat tower cap to tower can also leak. if you still have a black plastic original fit tower in place, go easy. The plastic falls to pieces give age,and heat. The tower cap is removed using as I remember a 10mm hex allen key. The plastic can chew out and suffers with age. Refilling the coolant is via that cap and the header tank. Leaks can occur with the cap seal and also down at the tower base where you will find four 8mm bolts securing it to the inlet manifold. Between the two units is an O-ring seal. Again, it can leak. Most of us will recommend fitting an after market ali tower as a replacement. Prices are similar to the original plastic unit and solves the above issues and that of spinning bolt "nut " inserts which make dismantling difficult when thermostat changing is envisaged.

If you fit a new tower, two of the mounting bolts remove easily, the rear two are obscured by the inlet manifold. Bend an 8mm spanner by about 85 degrees near the ring spanner end. That allows the bolts to be removed without lifting the inlet manifold. A great tip is that one. Bent spanner known to us in the JEC as a "Jenner Joggler" named in honour of its inventor....Club Chairman, Rob Jenner!

You will find more details and pictures of fitting these parts in the Cooling System of the S-type BB where I have documented the procedures.

Hope this gives you some leads on your leak issues. I think you will find most emanate from around the water pump and thermostat tower areas and their associated pipes and connections. good luck. If all else fails, a dose of K-seal as used by the AA and myself, can cure the most obstinate of leaks and running fans! It has to be squirting out somewhere. You just have to find it!!

Mike K

[aaj]

A few corrections (re differences between the S Type & the XK8) to Mike K's ditty above.

1. The XK8 uses a different Tensioner on the serpentine belt and there is insufficient room to get a torque wrench & socket between the tensioner & the cooling fans. You will need an extra long 15mm combination spanner (suitable spanners keep appearing on e-bay for around £10 incl del for a good quality item i.e. Britool) to de-tension the belt. (or remove the fan pack)

2. It would appear that Jaguar used different bolts on the 'tower' (or the Inlet Manifold is different) as on the XK8 the Inlet Manifold has to be loosened to allow the 2 rear bolts to come free (remember to shorten the rear bolts before refitting for future maintenance). The Inlet Manifold Seals (8 No) get less pliable with heat & age so replacement of these is the order of the day (or you may get funny error codes regarding weak mixture etc.).

I cannot confirm/challenge if the Jenner Joggler will work as I used a small spanner.

Allan J

[PTR200Jag]

Thanks very much, Mike, Allan, information much appreciated......

Will investigate the suspected leak area once I get it up on some ramps which will happen soon as my next jobs revolve around cleaning up the underside of the wheel arches / floor / sills and repainting sealing as necessary.

[PTR200Jag]

Its been sometime since I posted this originally but I have now discovered the source of the leak.... as it has worsened to the point of "visible" !!

The plastic ( ) thermostat housing has sprung a leak in the hex head orifice within the lid

I haven't seen it until today when i lifted the bonnet to check the oil... there, staring at me was a puddle on top of the lid, just started to run down the sides. After cleaning it up a little you can still see the coolant track.



When the engine is at temperature, coolant comes out very slowly and obviously fills the hex head opening up and then flows over the top... this must take some time, 100 miles plus... as I checked it around that point and it was not evident then.

Just got to decide the next move now

[Brakebuster]

not too bad

you can buy the whole tower in aluminium for under £50 , and it will take about an hour to fit

i would also buy a new stat , and carefully inspect the hoses, and replace if required( jiggle pin to the top )

also a good excuse to change the coolant , as that should be done every two years

while you at it, ensure the water pump is good , if not, do it now, save the coolant having to be done again

BB

[PTR200Jag]

Thanks for that, ordered a complete kit... guess what I am doing this weekend

[J44EAG]

Watch for the very sharp top thread end on the top of the tower. The cap is supplied with an O-ring which I have found gets easily pinched when tightened down to the correct torque. In my opinion it is the wrong seal for the job and can damage easily and even slip down into the tower. I tried a piece of rubber sheet which was unsuccessful and ended up with a red fibre wide and flat washer. That works well without leaking but is susceptible to easy wear when tightened onto the sharp top edge of the tower. Dress off with a file to reduce the sharpness.. Best to size the washer and buy a few spares for future use.

The ali tower is identical in all respects to the old plastic type and fits easily to the car. Use a bent 85 degree ring spanner to avoid having to lift the inlet manifold to get the rear two bolts removed or refitted.

Filling and burping of air from the system is accomplished via the tower and the header tank. Check for a copious amount of coolant returning to the header tank via a rubber hose.

Mike K