Hi Everyone,

We started having problems the other week with a squeal on start up and then it started to last a little longer every day.
We put a new belt and a new tensioner on and now it has turned into constant squeal.
Around the same time of having this problem the Mrs was going to work and had to pull over on the motorway because it was overheating or appeared to be after about 10 mins she turned the key and everything went back to normal so she carried onto work.
When she left work the same thing happened again apart from this time she managed to get to the services and left it for nearly an hour to cool down before continuing to get home.
I've checked for air locks and the hoses and found nothing I've also put 2ltrs of coolant in and it ran as normal for a couple of days but still with the squeal on start up.
While it was running ok the Mrs was on the motorway doing 65mph when she said it felt as though it was miss firing and holding back so when she came back we had the Injector loom checked and replaced as it looked like it had its own oil supply. That seems to of sorted the miss fire and I thought it might sort the belt squeal as it was throwing a little bit of oil onto the belt but no it didn't it got worse.
Now it gets hot within a few miles now and still screams its head off.
Can somebody please advise me where to look next I thought about the Alternator but that is charging like it should, the water pump or the pas pump but the steering is not affected, ace pump , crank pulley but which would affect the overheating.
This is making my head hurt

Hi, water pump or viscous fan would be the first calls, be prepared to loose some coolant but that's the best way to test it: when the symptom occures remove the bleed screw to see if there's pressure or not, if you rev it a bit it must push the coolant up to the bonnet, if it does remove the belt and see if there's no play in the viscous bearing... also only genuine(not OE nor aftermarket) belt will be silent, but here is some problem with something as it's overheating...provided it's not some coincidence..that "missfire" could have been due to the overheating cos the ECU reduces fueling if it gets high temp reading from the sensor even before the gauge leaves the middle...fix it ASAP as you might end up with a cracked head if you continue to use it so...also after some episodes of overheating the injector rubber seals will be on the way out as well

Thanks for the reply sierrafery.

It sounds like it could be an accumulation of things that is causing the main problem.

The Disco hasn't moved now for a day or two now and wont until its right.

Finally got around to looking into whats causing the scream and overheating yesterday.

I thought it best to find out where the noise was coming from first I've ruled out the belt and tensioner as they have only been replaced about three weeks ago with genuine parts.

On start up the noise was coming from the area of the Ace pump, Pas pump and the AC pump. I then checked the top hose bleed nipple to see if coolant would spurt out but I got nothing not even a dribble.
After a few minutes the screeching stopped and with the bleed nipple still out the coolant spurted at a constant rate for a few seconds until I put it back in.

When after about a minute the screech came back again I stopped the the engine and took the belt off.
I turned the pulleys by hand on the three pumps and they all were turning freely when until I turned the Ace pulley and that just went very stiff after a few turns and then freed off again. This happened for quite a while
I've ordered a new pump and should fit that today.
Has for the overheating well I haven't got to the bottom of that yet I don't know if having a failed pump pulley would cause the belt to slip over the Pas pump pulley which would cause the water pump not to work.

how come you didnt top up coolant

aaaaaarrrrghhhhhhh ... imo you'll have a spare good ACE pump then cos that's how that pump acts as you've described, the reason is in the quoted part:

The pump is of the radial piston type which delivers fluid at high pressure.
The radial piston pump has six pistons located in bores in a cylinder housing. A central shaft, which is driven by a pulley and the auxiliary drive belt, has a cam which operates the pistons as it rotates.

Click to expand...

the most common fault in that area is the viscous fan's bearing, jiggle up-down the fan see if there's play in it or not

sierrafery said:

aaaaaarrrrghhhhhhh ... imo you'll have a spare good ACE pump then cos that's how that pump acts as you've described, the reason is in the quoted part:


the most common fault in that area is the viscous fan's bearing, jiggle up-down the fan see if there's play in it or not

Click to expand...

I won't have a spare I pressed the central shaft out after I ordered the new one to see what was inside and besides the bearing inside being knackered probably through pressing the shaft out there is a lot of scoring and filings inside the housing as well.
Now I know how to check the viscous bearing I'll check that when I go and put the the pump on.
Thank you for your reply

jamesmartin said:

how come you didnt top up coolant

Click to expand...

I did top the coolant up even though I didn't mention it.
Thanks for the reminder though.

mrfreeze said:

I won't have a spare I pressed the central shaft out after I ordered the new one to see what was inside and besides the bearing inside being knackered probably through pressing the shaft out there is a lot of scoring and filings inside the housing as well.
Now I know how to check the viscous bearing I'll check that when I go and put the the pump on.
Thank you for your reply

Click to expand...

i'm glad i was wrong then... well done

sierrafery said:

i'm glad i was wrong then... well done

Click to expand...

You still could be right I think it could be a few things and changing the belt and the tensioner has brought the problems to the surface.

I'll still check the viscous bearing like you advised before I start it up again though just to be on the safe side.

I'm still worried over the overheating issue though as I think that could be another issue

for the overheating bleed it well then:
1. make sure that the tank's cap is well tightened otherwise it will not keep the pressure at 1.4 bar and then from 95*C the coolant will start bubbleing and release air in the system, that cap is VERY important cos it has two sealing o-rings and a pressure valve which must keep 1.4 bar steady in the system cos then the boiling point of the water goes up to 123*C, if the cap fails either way there will be overheating or overpressure... the best would be to put a new one to rule it our 100%

2. when the gauge is at the middle try to stop the viscous fan at idle with a rolled newspaper, if it stops it means it doesnt lock just freewheeling and it's not enough cooling effect then

these are the simple things

sierrafery said:

for the overheating bleed it well then:
1. make sure that the tank's cap is well tightened otherwise it will not keep the pressure at 1.4 bar and then from 95*C the coolant will start bubbleing and release air in the system, that cap is VERY important cos it has two sealing o-rings and a pressure valve which must keep 1.4 bar steady in the system cos then the boiling point of the water goes up to 123*C, if the cap fails either way there will be overheating or overpressure... the best would be to put a new one to rule it our 100%

2. when the gauge is at the middle try to stop the viscous fan at idle with a rolled newspaper, if it stops it means it doesnt lock just freewheeling and it's not enough cooling effect then

these are the simple things

Click to expand...

So are you saying that it should be quite difficult to stop the fan with the paper as it should be spinning with the power transmitted from the engine rather than the tension from the belt?

it'e not as simple as it seems, it's a viscous coupling unit which locks the fan as the engine gets hot and it's freewheeling when it's cold...so yes, it must rip the rolled paper with warm engine ...if you can stop it it's gone ... RTFM
[QUOTE="COOLING SYSTEM - TD5 ;DESCRIPTION AND OPERATION 26-1-9" ]The viscous fan provides a means of controlling the speed of the fan relative to the operating temperature of the
engine. The fan rotation draws air through the radiator, reducing engine coolant temperatures when the vehicle is
stationary or moving slowly.
The viscous fan is attached to an idler pulley at the front of the engine which is driven at crankshaft speed by the
auxiliary drive belt. The fan is secured to the pulley by a nut. The nut is positively attached to the fan spindle which
is supported on bearings in the fan body. The viscous drive comprises a circular drive plate attached to the spindle
and driven from the idler pulley. The drive plate and body have interlocking annular grooves with a small clearance
which provides the drive when silicone fluid enters the fluid chamber. A bi-metallic coil is fitted externally on the
forward face of the body. The coil is connected to and operates a valve in the body. The valve operates on a valve
plate with ports that connect the reservoir to the fluid chamber. The valve plate also has return ports which, when the
valve is closed, scoop fluid from the fluid chamber and push it into the reservoir under centrifugal force.
Silicone fluid is retained in a reservoir at the front of the body. When the engine is off and the fan is stationary, the
silicone fluid level stabilises between the reservoir and the fluid chamber. This will result in the fan operating when the
engine is started, but the drive will be removed quickly after the fan starts rotating and the fan will 'freewheel'.
At low radiator temperatures, the fan operation is not required and the bi-metallic coil keeps the valve closed,
separating the silicone fluid from the drive plate. This allows the fan to 'freewheel' reducing the load on the engine,
improving fuel consumption and reducing noise generated by the rotation of the fan.
When the radiator temperature increases, the bi-metallic coil reacts and moves the valve, allowing silicone fluid to
flow into the fluid chamber. The resistance to shear of the silicone fluid creates drag on the drive plate and provides
drive to the body and the fan blades.[/QUOTE]

Thank you for that I appreciate the advice you've given me on this.
I'll let you know how I get on after I've done the pump

I changed the Ace pump today which made a bit of a difference but not the way I wanted.

The screech more or less went and was replaced by a chirp on start up and when I turned it off it has started to rattle.

Took the viscous fan off to see I could get any sort of movement from the bearing and it has a slight rock of perhaps 0.5mm from left to right so I took the bearing out and ordered another which I pick up tomorrow.

I still don't know if this is going to cure the overheating issue or could I be looking at changing the Crank Pulley as well

I hope I don't have to change that I've been quoted around £400.

Fingers crossed for the bearing tomorrow

Sierrafery I said you could still be right and you are.

I think changing the belt and tensioner as highlighted a few small problems which have all come to light at once.

The engine itself has covered 166,000 miles so I would expect a few small issues.

unfortunaetely the crank pulley could make tricks and it's expensive, the genuine has an indecent price so i went for britpart from island4x4 which was 250quid tax included at around the same mileage as yours, i can't complain untill now(around 20k miles)... also i can tell without doubts that the ONLY reliable belt is the genuine one

Yeah I agree with the belt but to be honest I only ever put genuine parts on all my vehicles past and present.

The Viscous Fan Bearing was replaced today and now I have to replace the Crank Pulley.

There is still a screech on start up that lasts about 10 seconds ut when you rev it, it quietens down to nothing so almost there.

When I turn it off there is distinctive rattle so it has got to be the Crank Pulley.

What I can't get my head round is the bloody price:jaw: of the things.

Ah well I'll have to see if I can get hold of one on Monday now.

Well finally got around to fitting the Crank Pulley on Friday and to say I'm fed up is an understatement.

I've got rid of the screech but I've still got the the rattle when the ignition is turned off.

I haven't a clue where this is coming from it sounds as though its low down at the front of the engine but there's nothing left to change.