M54 engine viscous fan. Not sure if I have an issue.

[Mint]

@Pond, if you do change the viscous coupling don't forget that the big nut is a left hand thread.

 

[Ianmc]

Why not delete the viscous fan, it doesn't seem to be needed? Or just leave as is.
Whilst no real comparison, my M44 only has the electric (aircon) fan and has no other fan installed from factory.

 

[Nodzed]

The M54 primary cooling was by viscous, if it didn't have AC the electric fan wouldn't be fitted. Always better to have both systems if they are there, always a back up if the primary fails, I deleted the viscous on my M, under normal and vigorous driving all was OK, but under prolonged high revving very vigorous driving the electric fan didn't cope well, hence I put it back. I would leave things as Mr. BMW designed it, I'll wager he knows better than us.

 

[Pond]

I have ordered a new viscous coupling (£40).
I noticed there are several 'versions' available; some say they are for 'hot climates' and some also say they are for 'no electric fan', even though realoem only gives one part number.
I can only presume the bimetallic strip on some move at different temperatures to others??

I have ordered a 'generic' one with the correct part number, so let's hope it makes a difference.

 

[Nodzed]

I have ordered a new viscous coupling (£40).
I noticed there are several 'versions' available; some say they are for 'hot climates' and some also say they are for 'no electric fan', even though realoem only gives one part number.
I can only presume the bimetallic strip on some move at different temperatures to others??

I have ordered a 'generic' one with the correct part number, so let's hope it makes a difference.

If you don't have a set I would highly recommend getting one. Makes the job a lot easier.
And as Mint said, its Lefty Tighty Righty Loosie

Viscous Spanners

 

[Pond]

So....I changed the viscous coupling today for an item with the correct part number (didn't get it from BMW and it isn't a 'recognised' brand).
Now I have the opposite problem!
At idle in my garage (ambient about 15c) it won't get to temperature. I ran it for an hour and a half and it got to 75c ish. The viscous clutch is making at around 65c and it creeps up to 75 ish with the fan running pretty fast all the time.
I was under the impression there should be virtually no heat in the rad until the thermostat opens (90c ish??). I am now wondering if my clutch is the wrong one AND my thermostat is letting by.

It's starting to get on my tits now.

 

[Nodzed]

You said before that the aux fan was coming in and out, now its not. Sounds like the viscous is working fine now. If there is no airflow maybe the below is causing


The stock BMW M54 thermostat, often considered the "tropical" variant, opens at around 97°C (207°F), but the M54 engine also incorporates an engine management system that can open the thermostat earlier to a computer-controlled temperature for increased power. This is a map thermostat that can be commanded open by the DME to reduce coolant temperature when high power is requested.
Understanding the thermostat's operation:
Map Thermostat: The M54 engine uses an electronically controlled thermostat, sometimes referred to as a "map thermostat" or "electronic thermostat".
DME Control: The Engine Control Unit (DME) can command the thermostat to open at different temperatures depending on the engine's demand.
Coolant Temperature Management: When the DME determines maximum power is requested, it can signal the thermostat to open at a lower temperature than its standard 97°C, resulting in a cooler coolant temperature.
Normal operating temperature:
While the thermostat's primary opening point is around 97°C, the engine's normal operating temperature typically fluctuates between 90-95°C.
Temperatures can temporarily rise to around 100-105°C, especially in hot weather or heavy traffic.
Key takeaway:
The BMW M54 thermostat doesn't have a single fixed opening temperature; it can open earlier than its stock 97°C setting at the command of the engine's computer to help the engine achieve maximum efficiency and power when needed.

 

[Duncodin]

. . .
. . .
I ran it for an hour and a half and it got to 75c ish. The viscous clutch is making at around 65c and it creeps up to 75 ish . . . . . .

You're not measuring this by your own addon temp sensor mounted way down low by the radiator drain plug? I assume you needed a temp sensor for the temp gauge of your rebody ferrari style dash having lost access to the stock Z3 gauge. But down there you're just measuring the temp of water leaving the bottom of the radiator which is not the actual block temperarure.

 

[Pond]

You're not measuring this by your own addon temp sensor mounted way down low by the radiator drain plug? I assume you needed a temp sensor for the temp gauge of your rebody ferrari style dash having lost access to the stock Z3 gauge. But down there you're just measuring the temp of water leaving the bottom of the radiator which is not the actual block temperarure.

The measurement is via my code reader, but I don't know which sensor it is taking the info from. There are two 'original' sensors; one in the middle of the radiator and one under the intake manifold. My 'gauge' sensor has not replaced anything, it is screwed into the drain plug.
I am not taking any notice of my gauge, as I consider this a guide only.
I have removed both of the BMW oil sensors; temperature and pressure, and replaced them with aftermarket which are not connected to anything except my gauges.
Could it be that my lack of oil info is messing with the DME?

 

[Pond]

The stock BMW M54 thermostat, often considered the "tropical" variant, opens at around 97°C (207°F), but the M54 engine also incorporates an engine management system that can open the thermostat earlier to a computer-controlled temperature for increased power. This is a map thermostat that can be commanded open by the DME to reduce coolant temperature when high power is requested.
Understanding the thermostat's operation:
Map Thermostat: The M54 engine uses an electronically controlled thermostat, sometimes referred to as a "map thermostat" or "electronic thermostat".
DME Control: The Engine Control Unit (DME) can command the thermostat to open at different temperatures depending on the engine's demand.
Coolant Temperature Management: When the DME determines maximum power is requested, it can signal the thermostat to open at a lower temperature than its standard 97°C, resulting in a cooler coolant temperature.
Normal operating temperature:
While the thermostat's primary opening point is around 97°C, the engine's normal operating temperature typically fluctuates between 90-95°C.
Temperatures can temporarily rise to around 100-105°C, especially in hot weather or heavy traffic.
Key takeaway:
The BMW M54 thermostat doesn't have a single fixed opening temperature; it can open earlier than its stock 97°C setting at the command of the engine's computer to help the engine achieve maximum efficiency and power when needed.

OK but all of my trials are at tickover which doesn't make sense. And the viscous clutch is purely mechanical, operated via temperature, so is independent of whatever the car is doing (apart from spindle speed which is directly driven by the crank).

I really need to drive the car and see if it gets to temperature and maintains it. I may be chasing a problem which doesn't exist.

 

[Duncodin]

I still have my original z3 gauges. When I cruise round town, traffic etc. I hear the viscous fan when it's engaged. My temp gauge, even when idling, never quite reaches the middle marker. I have no idea what temperature it is showing ut i think below center seems a little low. I suspect my thermostat is duff. But even though it's low my fan still comes on.

But it doesn't worry me. I'll be replacing all the pipes and hoses eventually so will do the thermostat then anyway. but as far as I'm concermed it's all working ok enough till I get round to it.

 

[Pond]

The saga continues.....I am sure I have a cooling issue but am still not sure where, or why.
The new viscous clutch is maintaining the coolant at around 75c. That's too cold, surely??
I took the car for a 20 mile drive today (19c ambient), in town and on a few open roads. The coolant never got above 75c (ish), nor did the oil (obviously). The oil pressure remained high presumably because the oil wasn't getting to full operating temperature.
It seems as though my new viscous clutch 'kicks in' at around 60c!!

I think I have a 'leaky' thermostat and the fan is overcooling as it is cooling coolant from a lower temperature to start with.

My original viscous clutch is going back in tomorrow, as I have checked the bi-metallic strip with a heat gun and it opens and closes the pin. The strip was covered in crud when I removed it (which I couldn't see when installed), which I'm hoping was stopping it working correctly.

The ONLY thing, apart from the cooler engine temps, I noticed was that the car seemed to be more powerful today than it has been of late. It really pulled hard from about 2,500rpm; much more than usual. I don't know if that is my imagination, or because the old fuel has now been completely burned and it's running on V-power only, or if it's the cooler engine temps, or something else!!!

I know nothing about engines, cooling, or a lot else really, but surely something is not right here?

 

[the Nefyn cat]

but surely something is not right here?

Yes, indeed. Although this will be no help, and others who obviously know my car better than I do will tell you I'm wrong, I've gone the last few years without a fan at all and, as far as I'm aware, it still works. I didn't notice any mention of actually taking one of these new-fangled IR temp gauges to various parts of the engine and seeing what is happening. The temp never going above 75 is not good, and points towards a defective thermostat, easily checked by taking it out, warming it up in a pan of water, (best done when no fussy people are watching) and seeing when it opens.
Something like this will do

Pardon our interruption...

It will also give you hours of fun should there be a cat available.

 

[Pond]

I have changed the viscous clutch back to the old one. It is now doing what it was before; getting to 95c, the electric fan kicking in and dropping it back to 87c. The viscous fan spins but not fast. At least it maintains a good temperature like this, rather than a miles too low one.

My guess is the viscous fan is not operating correctly AND I have a leaky thermostat. I shall see how it goes!

 

[Duncodin]

The temp never going above 75 is not good, and points towards a defective thermostat,
. . .

Agreed

. . .
. . . easily checked by taking it out, warming it up in a pan of water, (best done when no fussy people are watching) and seeing when it opens.
Something like this will do
. . .

Also correct but, TBH, If I went to the trouble of undoing the thermostat housing and taking out a 25 year old thermostat then I'd put a new one in anyway.

 

[the Nefyn cat]

Indeed. However, back when I was doing my mechanics aprenticeship I was taught to find out what was wrong first, not to just fit a bunch of parts in the hope that something would cure the fault. I've seen people waste loadsamoney on throwing bits in and still having the original problem. And it's quite nice to do a bit of diagnosis that finds a fault and fixes it. Normally cheaper, too.

 

[Andyboy]

If your viscous coupling is old, black and ugly, it's finished. The black is the oil that gradually seeped out and attracted road grime. They're 50 quid new - if in any doubt, buy a new one.

 

[Pond]

I was taught to find out what was wrong first, not to just fit a bunch of parts in the hope that something would cure the fault.

You wouldn't get a job in a dealership (or any service sector) these days. That attitude is not conducive to big profits. I have this argument almost every day with the idiots that work for me!

 

[Pond]

If your viscous coupling is old, black and ugly, it's finished. The black is the oil that gradually seeped out and attracted road grime. They're 50 quid new - if in any doubt, buy a new one.

It's clean and quite shiny actually. It was just a bit of grime on the metallic strip. I cleaned that and it made no difference whatsoever.
I did buy a new one.....it made matters worse!!

 

[the Nefyn cat]

Not after a job at a stealer, far to much of a conscience for that. Too old, too. And since this is your own car, at home, you would still be better off finding an actual problem and fixing it. Bear in mind that a car sat ticking over will never heat up as much as when it's being driven, so any amount of sitting running for 90 mins won't bring out any problems.
Like I said earlier, mine hasn't had a fan for a few years now, and still copes with living near Snowdon entirely happily.