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[Scatmancraig]

Temperature gauges often lie about what's really going on. Specifically, they have a dead point around normal operating temperature so the needle doesn't move too much with the normal fluctuations of temperature and panic the driver.

No experience of the TD's gauge, but bear that in mind.

Sounds like you've made an improvement. If the viscous fan gets annoying, bear in mind that many TD drivers report that it works perfectly well with just the electric fan. Store the viscous fan vertical if you do decide to remove it.

I removed the old fan previously, and the engine got a little too hot for comfort, to the point where the electric fans were coming on at low speed after a short but spirited drive.  It was at this point I broke the original viscous as I removed the bi-metallic strip in the centre.  I thought it would be like a Senator/Carlton unit where the fan assembly is held to the shaft by an allen headed bolt under the strip.  I refitted it, but the viscous fan was then on all the time as I'd bent the strip to the point where the little button under it wasn't pressed in at all.  I still refitted it as it was though, better to have the fan on all the time than not at all.

The replacement fan, a second hand unit off Diamond Black Geezer, was initially working in exactly the same way as the one that came off (before I broke it), i.e. it would be silent until you'd driven the car for about 4 miles, then it would kick in.  Definitely not the case now, thankfully.

Same with me, I reckon a new stat would help my engine, but there's nothing apparently wrong on the temp gauge... pinch of salt, really, I think. I does sound like Mr Scatman has done good. 

I can't remember the name of the product I used, other than it wasn't the Holts stuff I'd been advised not to use.  The instructions said to add it to the header tank and leave the engine ticking over for 15 minutes.  I wasn't holding out any hopes, and the liquid I drained was brownish, but no sludge to speak of.  But as the cooling system was 100% water for the past week, it maybe has dislodged a bit of crud, and the added bonus of having proper new coolant in the system would also help. 

To drain the system, I removed the smaller bottom hose that sits next to the drain plug on the passenger side of the rad.  God knows how you're meant to get the drain plug open from the position its set in, there isn't enough room to grip it to turn, or get a screwdriver in the slot!  Don't forget that I previously removed the radiator from the car and took it to the local jet wash to clean it externally, I also turned it both ways up and ran a hose through it, plenty of brown shite came out then, so I guess most of the remaining crud was hiding in the rest of the cooling system.  I also flushed the system out with a hosepipe last Saturday, so from then till last night it had clear water in it.

Once I've changed the oil, I'll give it a good blast up the bypass and see if it starts to get hot again.  The viscous fan can remain on for the time being, I main even drain the coolant again in a few weeks just to be sure.

[Diamond Black Geezer]

Happy days. Glad that fan is a good 'un, anyway 

[Diamond Black Geezer]

Just looking at the Howto re: flushing out the coolant/HBV/heater matrix etc... and it mentions that you can't 'fully flush out' the system without removing the water pump...that's interesting. How did you remove all traces of the cleaning agent, was it literally sitting there with a gardenhose in the top, and the hose off at the rad, sort of thing? Ta 

[Scatmancraig]

Well I thought it was too good to be true.   This viscous fan kicked in again on my journey home from work, during normal stop start driving.  A short burst of foot to the floor driving also saw the gauge climb quickly, although only up to an 'indicated' 95, by then I was fast approaching a 30 milit so had to back off sharpish!

I was going to change the oil anyway today, so got that out of the way when I got home, can't do any harm if it doesn't do any good.  Noticed that the centre of the radiator (the bit directly in front of the fan) is cold, but the viscous fan still remains locked in.  Both edges of the radiator are quite warm though, is this normal?  Or have I got some sort of restriction in flow around the coolant circuit.

I'm reluctant to believe that the water pump has failed completely, as surely if it had, the car would boil up quite easily, which it doesn't.  There's barely any pressure at all in the header tank if you release the cap just after switching the engine off.  You can drive it all day as it is, and providing you don't thrash it, the temperature remains what I consider to be normal at just over 90.  Even in traffic it never goes higher than 95, and soon goes back to normal when moving again.  Is it possible for the pump to get less efficient over time?  Or is there an issue with the thermostat?  I guess a sticking thermostat would cause the engine to get excessively hot and not allow water to pass through the radiator, so maybe its worth taking it off to see.  Is there any way of testing the water pump without removing it?

What exactly activates the viscous fan?  Is it the heat from the engine passing through the metal shaft and releasing the switch, or hot air passing through the radiator?  And where is the thermostat on these engines?  Is it under the cover on the front of the block, just to the left hand side a little?

Any further advice would be much appreciated!

[Nick W]

That still sounds like a coolant flow issue to me.


Your short lived improvement from flushing the radiator suggests that you were on the right track, and once again proves that chemical coolant flushes aren't particularly effective. A new radiator would be the cure if you were certain it is the fault, but unfortunately isn't something you can easily check.


A failing waterpump due to a loose or damaged impeller is easy to check, common and cheap to fix. I would remove it just to be certain.


Finally viscous fans: my understanding is that they only turn at low RPM and have little to do with temperature sensing. This explains why you can normally hear a faulty fan coupling from the racket it makes over the 2500(ish) RPM it isn't designed to work at. A new coupling is also cheap, and new BMW waterpumps won't be warranted without a new one.

[Scatmancraig]

That still sounds like a coolant flow issue to me.


Your short lived improvement from flushing the radiator suggests that you were on the right track, and once again proves that chemical coolant flushes aren't particularly effective. A new radiator would be the cure if you were certain it is the fault, but unfortunately isn't something you can easily check.


A failing waterpump due to a loose or damaged impeller is easy to check, common and cheap to fix. I would remove it just to be certain.


Finally viscous fans: my understanding is that they only turn at low RPM and have little to do with temperature sensing. This explains why you can normally hear a faulty fan coupling from the racket it makes over the 2500(ish) RPM it isn't designed to work at. A new coupling is also cheap, and new BMW waterpumps won't be warranted without a new one.

Yes it definitely seems to be a flow issue like you say.  I have removed the radiator once before, and plenty seemed to be coming out of either end when you ran water through it.

With regards to the viscous fan, there's a bi-metallic strip across the front of them, which keeps a small plunger depressed.  When the metal strip heats up, it bends slightly, thus allowing the plunger to rise, then locking the fan on.  My old fan worked exactly the same as my current fan, until I removed it and accidentally bent the strip so that the plunger was out all of the time.  hen I refitted the fan, it was locked in all the time. 

Is the waterpump easy to remove on the TD engine?  I have no Haynes manual as guidance.  Well actually I do, but only for petrol Omegas.  Just had a quick look for water pumps and they do seem cheap enough.  I wonder if they are Omega specific, or will one from a BMW 325 or 525tds be identical (loads more to choose from then!). 

[Nick W]

The pump seems to be pretty much the same(it may even be the same) as BMW petrol sixes. In which case, you remove the fan coupling, undo 4 bolts, and knock it off with a mallet. The mallet is quicker and easier than using the provided tapped holes to draw it off.

[Scatmancraig]

The pump seems to be pretty much the same(it may even be the same) as BMW petrol sixes. In which case, you remove the fan coupling, undo 4 bolts, and knock it off with a mallet. The mallet is quicker and easier than using the provided tapped holes to draw it off.

I've just read an article on a BMW forum about it.  Looks an easy enough job.  Water pump prices aren't bad either, although I guess that ones with metal impellors are better.  I'm guessing my issue is either a failed or partly failed water pump, or a partly blocked radiator.  Water definitely passes through the radiator, I can blow through the system from one side to the other, and plenty comes out the opposite side.

[Nick W]

The pump seems to be pretty much the same(it may even be the same) as BMW petrol sixes. In which case, you remove the fan coupling, undo 4 bolts, and knock it off with a mallet. The mallet is quicker and easier than using the provided tapped holes to draw it off.

I've just read an article on a BMW forum about it.  Looks an easy enough job.  Water pump prices aren't bad either, although I guess that ones with metal impellors are better.  I'm guessing my issue is either a failed or partly failed water pump, or a partly blocked radiator.  Water definitely passes through the radiator, I can blow through the system from one side to the other, and plenty comes out the opposite side.

The only problem is that doesn't prove that the water is flowing through the radiator in a manner that will cool it. it can still be badly silted up.

[Scatmancraig]

The only problem is that doesn't prove that the water is flowing through the radiator in a manner that will cool it. it can still be badly silted up.

I agree.  I'm not 100% sure which direction the water is supposed to flow in either.  Water would appear to come through the big top hose on the passenger side, and out of the big bottom hose on the drivers side.  But then there's the two smaller hoses, that are attached to what appears to be an electric auxilliary pump, the top one being on the drivers side, the bottom on on the passenger side.

The viscous stayed silent again this morning, so at least there's been some sort of an improvement over previously.  I need to go on a slightly longer journey from cold to see exactly how long it does take for it to cut in now.  The journey home last night was interrupted by a short stop to collect my oil filter.  It was after this stop when the viscous kicked in. 

What purpose does the auxilliary electric pump serve, and would it affect things in any way if it wasn't working?

[Scatmancraig]

On a related matter, what is the purpose of what appears to be an electric auxiliary water pump mounted on the drivers side inner wing, alongside the fuel filter?  It is connected to two smaller diameter hoses, one of which goes to the top of the radiator on the drivers side, the other appears to be connected to the small lower hose on the nearside of the rad, just above the drain valve.  I've never had a car with this type of device fitted, I was wondering exactly what purpose it serves, and whether if it had failed, would it have any effect on the problems I'm having?

I've ordered a new main water pump anyway, it was cheap enough.  No idea if it has a plastic impellor or not, but even a new one with plastic impellor ought to be better than one that has failed.  When it arrives, I'll take the rad off once more and try and flush it again to see if any more brown crud comes out like it did the first time. 

[TheBoy]

you can drop to 25-75 (or even less) for summer

No, no, no, no, no. NO.

No.

No.

NO.


In case that was unclear, NO.

[Doctor Gollum]

1. Does it have aircon?

If no, move to last question.

2. Does the front fans work?

If no, find out why. If yes, go to next question.

3. Does the compressor work as expected?

If yes, skip to last question.

4. Is the aircon gassed, or has it recently been done?

If yes, skip a question.

5. Get it regassed.
 
6. Does it now all work as it should?

If yes, go to last question.

7. Does the condensor leak?

If yes, order one when you order your radiator.

8. Have you fitted your new radiator yet?

  

[Doctor Gollum]

Whilst my last post may seem flippant, it does raise a genuine point...

If your aircon, assuming fitted, doesn't work, then the lack of additional cooling effect from the extra fan or two may well be limiting the effectiveness of the radiator, even more so if auto with a separate cooler.

Leaving the working aircon in Eco mode has the same effect as it not working... ie the auxiliary fans will be off.

If you don't care about aircon, then remove the condenser keeping the front fans and fit an inline switch to the fan circuit in lieu of the aircon ecu input.

A new radiator is easy enough to fit, but to change the condenser requires radiator removal, hence the question

[Scatmancraig]

Whilst my last post may seem flippant, it does raise a genuine point...

If your aircon, assuming fitted, doesn't work, then the lack of additional cooling effect from the extra fan or two may well be limiting the effectiveness of the radiator, even more so if auto with a separate cooler.

Leaving the working aircon in Eco mode has the same effect as it not working... ie the auxiliary fans will be off.

If you don't care about aircon, then remove the condenser keeping the front fans and fit an inline switch to the fan circuit in lieu of the aircon ecu input.

A new radiator is easy enough to fit, but to change the condenser requires radiator removal, hence the question

It is auto, and it does have aircon, but there's no gas at all in the system.

I have tested the twin fans, both work at low and high speeds.  I did remove the viscous altogether for about a day, but this resulted in the electric fans coming on at low speed after a relatively short drive.  I wasn't happy with this as I felt they shouldn't have come on at all, but at least it proved that they do work.  I refitted the viscous, which by this time had decided to lock up permanently as i'd managed to damage the bi-metallic strip that activates it.  This has since been replaced with one that works properly.

The other day I opened the bonnet after getting home from work (viscous had already locked up).  The temp gauge was reading 92.5.  The centre of the radiator, i.e. the bit directly behind the fan, was stone cold.  The edges of the radiator were quite warm, particularly the passenger side end that has the larger hose at the top.  So either the radiator is blocked, the thermostat is stuck, or the water pump isn't pumping.   

I've already had the radiator out a couple of weeks ago, lots of brown water came out.  But it seemed to flow from one end to the other ok when I ran a hose through it. 

A water pump is on order, should be here today or tomorrow.  It may not need replacing, but I'm doing it for peace of mind and to eliminate it as the cause of the problem.

Where does the auxiliary electric pump come into the equation?  I've still no idea of its purpose!

Another question....  Is the radiator on the TD unique to that engine or the same as the petrol versions?  Mine has the integral oil cooler for the transmission, and connections for smaller hoses for the auxiliary pump.  Having never had a petrol Omega, I'm not sure of the set up.