Confirming a dead viscous fan?

[PiperZero]

Hello all!

Got stuck in traffic, and the temp needle creeps to a few mm short of red. Coolant level LED switches on to its red accusing glare.

Stopped, checked expansion tank, no sign of coolant Carefully opened the cap off and the water surges back into the expansion tank, with steam blowing up. Topped off with water, and drove back home.

Right - from searching thru this forum, looks like I have a dead viscous fan (temp goes up at standstill and idle, but cools down when moving). I flushed the coolant (removed top rubber hose from radiator, and poked a garden hose into expansion tank), started the engine and noticed that temp gauge hardly moves beyond 1/4 mark. The minute I re-connected the top radiator hose, took out the garden hose - temp creeps up to beyond 1/2 mark.

Beyond the viscous fan, anything else that I need to look out for? Thermostat? Waterpump?

If I have to replace the viscous fan, then I might as well change the thermostat and waterpump, which will lead to changing the timing belt while the front of the engine's laid bare naked anyways...

Anyways - Merry Xmas everyone!

[Pal318is]

To find out if your viscous is fubar'd...stick a long piece of wood into the fan, while the car is running, if you can stop the fan, then it's definately fooked, but if you can't, i'd look elsewhere. The thermostat being my first port of call.

HTH

Pal

[Pedromac]

Using a rolled up newspaper is a bit less brutal and minimises damage to the fan if it is working fine.

[gcorky]

To find out if your viscous is fubar'd...stick a long piece of wood into the fan, while the car is running, if you can stop the fan, then it's definately fooked, but if you can't, i'd look elsewhere. The thermostat being my first port of call.

HTH

Pal

lol ,using wood will bust your fan if viscous is good...rolled up newspaper is the tool required

[PiperZero]

Thanks guys! Yeah, the 'poke it with wood' method may raise some eyebrows in my carpark...I'll use the rolled-up newspaper trick and see how it goes. The last time I did this, fan still went on, but didn't really brutalized the paper (or was I chickening out and not poking hard enough? )

[Morat]

Make sure the engine is nice and warm, and apply the newspaper. You should have quite a lot of confetti

[PiperZero]

Hi folks, and merry christmas!

Has some free time over the weekend, so decided to do some R&D on the cooling system The viscous fan was still good, some paper confetti, but no woodchips...

This is the condition of the 2-post coolant temp sensor to the L-Jet ECU..

The connection was loose too.


Mine was a VDO unit, with '35C and 8 sec'. Anyone know what this means?


Bought a Bosch replacement along with the temp sensor for the temp gauge, and changed them. It's 24mm for the ECU sensor, and 19mm for the temp sensor...

[PiperZero]

Since flushing the cooling system is next, I also went and bought the thermostat as added insurance. It was the one with 70C stamped on. Since ambient temp here is around 32C, I thought getting the earlier-opening one was better (seems there's a 80C version?)



So, with 10mm socket in hand, cracked open (well, the previous mechanic didn't screw them in that hard) the thermostat housing and came up with this...

and this

[PiperZero]

So, with help from a pal, we'd changed the thermostat, the coolant temp sensor (to ECU) and temp sensor (to temp gauge) and started bleeding the system.

Well...either the engine's been eating some midnight snacks of beans or there's some major air in the cooling passages. Unscrewing the bleeder screw on top of the thermo housing caused at least a couple minutes worth of air hissing. Had to top up the expansion tank twice before water started coming out at the bleeder valve.

Checked the temp gauge, held steady at middle mark. Put BMW coolant in, checked the bleeder valve and hoses for leaks (none) and went for a blast round the park....Temp held steady, crept up to 3/4 mark in heavy traffic, but didn't heat up as quickly as before.

OK - so the R&D is half done, and will start on changing the hoses and viscous fan next...

[Brianmoooore]

Might be writing absolute rubbish because I know very little about old systems like L-jet, and I've just downed a glass or two of vino blanc, but I expect that your senor is a switch (set to open/close at 35 degrees) and passes a considerable current. The damage looks like it's been caused by a high current passing through a resistive joint, producing a lot of heat.
If I'm right, the connector to the sensor is likely to be damaged as well, and could well rapidly destroy the new sensor as well.

[PiperZero]

Brian, happy Xmas - must have been quite good vino blanc for you to refer to the sensor as Senor sensor..

If I need to change the connector, do I have to get an OEM version, or can I splice and solder (with heatshrink)? Not sure if there're blade connectors to fit such tiny terminals...

[Brianmoooore]

Wasn't a bad drop of vino - part of a ten litre box I brought back from holiday - straight from the vineyard..
Don't forget I might be totally wrong in this. The current through the terminals would have to be at least an amp to cause this sort of damage, and I suppose it's possible that whatever the switch/sensor feeds is faulty and drawing excess current as well.
Length of wire and connector from a scrapyard spliced on would be the easiest way to go. There are similar two pin connectors in several places which will do, although you might have to deal with the odd plastic indexing pin.

[Simon]

Or maybe the sensor it just the guage sensor, with a minimum temp reading of 35?

Judging by the state of your thermostat, it looks like the coolant system hasn't been very well cared for, and was well overdue a flush and change.

TBH, from the symptoms above, it doesn't sound too good, so keep an eye on the guage, coolant levels, excessive steam from the exhaust, and for any signs of mixing.

[Brianmoooore]

One too many pins on it to be the gauge sensor.
Just looked back at the symptoms, and can see what you're thinking Simon. Corroded water ways eating under the fire rings and pressurising the cooling system? Not good!

[Simon]

One too many pins on it to be the gauge sensor.
Just looked back at the symptoms, and can see what you're thinking Simon. Corroded water ways eating under the fire rings and pressurising the cooling system? Not good!

Ah yes, 2 pins!

Just suffered the same problem as the one above for the third time on my touring.

I'd bleed the system, top it up, and it would run OK for a couple of days before pressurising again, before it eventually started mixing.

[SCOTT325SE]

Corroded water ways eating under the fire rings and pressurising the cooling system? Not good!

This corrosion guys..... would it cause your coolant system to pressurise at any speed or just at higher speeds? Does it ALWAYS turn your oil into Mayo, or can it just run and run with a loss of water/pressurising of coolant system? Just curious on a topic of discussion with a friend of mine. His car is also an M20

[Simon]

Corroded water ways eating under the fire rings and pressurising the cooling system? Not good!

This corrosion guys..... would it cause your coolant system to pressurise at any speed or just at higher speeds? Does it ALWAYS turn your oil into Mayo, or can it just run and run with a loss of water/pressurising of coolant system? Just curious on a topic of discussion with a friend of mine. His car is also an M20

Water could be leaking into a chamber, and could run for a while this way.

[SCOTT325SE]

got ya.

[PiperZero]

Simon,
It's a sensor for the ECU, coz I also changed the other 1-pin sensor for the temp gauge. As for the cruddy mixture masquerading as coolant, yeah, I would love to smack the previous owner for such shoddy maintenance

Over the past few days, temp gauge has sat on mid mark during normal driving, with it creeping up to 3/4 mark (but slower than before the flush and sensor changes). Coolant level in expansion tank drops down a bit after a couple of days, which I suspect could be due to still more air in the system, or I've got leaky hoses somewhere.

Immediate plans would be to:
a) replace all hoses
b) flush cooling system again
c) change the viscous fan clutch (if I have any money left over)

Quite scared if I do have a crack in the head or any passages within the engine block

[SCOTT325SE]

or any passages within the engine block

check the plugs..... if one is almost completely clean, prepare yourself to change the engine... much like i am

[PiperZero]

or any passages within the engine block

check the plugs..... if one is almost completely clean, prepare yourself to change the engine... much like i am

Scott, I think I have the opposite problem...plug #6 (closest to driver) keeps fouling every 4-5 months. Been advised to do a compression test on all cylinders, so I'll have a chat with the mechanic soon...

Changing engines? Still M20 or M50? Options are pretty expensive this side of the world. GBP2400 for a M50B25 with manual box, inclusive of wiring and installation...

[SCOTT325SE]

M20 will be a straight swap pretty much. for that sort of money, I would either stick with an M20 or go all-out and drop in a V8 from a 5 series (the 4.5litre one)