Cooling fans won't shut off

[skynet]

Hi guys,

I had the cooling system replaced in my D. I bought a new alu radiator from Ed, along with new (or better to say, NOS) alu pipes, new silicone hoses, and a new otterstat.
Everything seemsto work fine, no leakages, but now the problem is: the fans turn on after some time (after reaching the trigger temperature) but will never turn off.
I have Joe Cool installed, the fans are working good, and if I shut off the engine and wait for say half an hour, then the fans won't come on after ignition, so the otterstat seems to work good.
I measured the temperatures of the hoses:
the one coming out of the radiator is 37 C (99 F)
the one coming back to the engine is 71 C (158 F)
and the one going back to the radiator (coming out of the engine) is 88 C (190 F)

The otterstat switching temps according to Eds are 85 and 92 C (185 and 198 F).

So the fans turn on when the coolant reaches 92 C (198 F) but as the coolant will never go below 88 C (190 F), it will never reach 85 C (185 F) and the fans will never turn off.

What should I do? Buy an otterstat with a higher temp range? (Here in Hungary there can be hot summers with temps over 40 C (104 F) so I don't know if this is a wise solution.)
Or does this indicate a bigger problem? There is no air in the systems, checked several times.

Thanks for your suggestions,
skynet

[DMCMW Dave]

Hi guys,

I had the cooling system replaced in my D. I bought a new alu radiator from Ed, along with new (or better to say, NOS) alu pipes, new silicone hoses, and a new otterstat.
Everything seemsto work fine, no leakages, but now the problem is: the fans turn on after some time (after reaching the trigger temperature) but will never turn off.
I have Joe Cool installed, the fans are working good, and if I shut off the engine and wait for say half an hour, then the fans won't come on after ignition, so the otterstat seems to work good.
I measured the temperatures of the hoses:
the one coming out of the radiator is 37 C (99 F)
the one coming back to the engine is 71 C (158 F)
and the one going back to the radiator (coming out of the engine) is 88 C (190 F)

The otterstat switching temps according to Eds are 85 and 92 C (185 and 198 F).

So the fans turn on when the coolant reaches 92 C (198 F) but as the coolant will never go below 88 C (190 F), it will never reach 85 C (185 F) and the fans will never turn off.

What should I do? Buy an otterstat with a higher temp range? (Here in Hungary there can be hot summers with temps over 40 C (104 F) so I don't know if this is a wise solution.)
Or does this indicate a bigger problem? There is no air in the systems, checked several times.

Thanks for your suggestions,
skynet


What fans are you using?
What is the outside (ambient) temperature during the tests?
Do the fans go off if you drive the car as opposed to letting it idle stopped?

[NightFlyer]

What temp thermostat are you running? Stock is 87C/187F. Thus, if you're running a stock thermostat in conjunction with your otterstat, yes, the fans are always going to be running so long as the thermostat is open.

Stock otterstat calibration is 97C/207F on, and 91C/196F off.

Personally, I think your otterstat range is far too low. I'd change it out for one that's calibrated to our specific application. Or, you could install a colder thermostat, but keeping the engine so cold also has it's detriments, such as not vaporizing moisture formation in the oiling system, which can lead to rust out of internal components.

Best luck :thumbup:

[Bitsyncmaster]

So the fans turn off when you shut off the engine? It takes quite a long time for the otterstat to cool with the engine off since your water pump is not running.

[skynet]

What fans are you using?
What is the outside (ambient) temperature during the tests?
Do the fans go off if you drive the car as opposed to letting it idle stopped?

Stock fans.
Ambient temp was cca 30 C (86 F), not too hot.
The fans don't seem to stop anytime.

[skynet]

What temp thermostat are you running? Stock is 87C/187F. Thus, if you're running a stock thermostat in conjunction with your otterstat, yes, the fans are always going to be running so long as the thermostat is open.

Stock otterstat calibration is 97C/207F on, and 91C/196F off.

Personally, I think your otterstat range is far too low. I'd change it out for one that's calibrated to our specific application. Or, you could install a colder thermostat, but keeping the engine so cold also has it's detriments, such as not vaporizing moisture formation in the oiling system, which can lead to rust out of internal components.

Best luck :thumbup:

Thermostat is stock, I suppose. It opens quite soon (this time at least, with ambient temp like 30 C/86 F).

The thing is, I checked the otterstat removed from the car and it has a marking "92/87". So it was also the lower range one. The cooling system worked ok with that otterstat.

So can the reason be the new, alu radiator not dissipating as much heat as the old, factory radiator?

Or maybe the new otterstat is not 92/87, but some degrees lower? Ed wrote "all is +/-".

[skynet]

So the fans turn off when you shut off the engine? It takes quite a long time for the otterstat to cool with the engine off since your water pump is not running.

When I shut off the engine but leave ignition on (I don't know if this is the correct wording), the fans continue to run, yes I know the water pump is not running so the collant has to cool by itself in the pipe that contains the otterstat.

They stop immediately if I remove ignition (turn the key to the left by another step).

[NightFlyer]

Your thermostat is opening and releasing hot coolant to the radiator at 87C/187F. Your otterstat is turning the cooling fans on at 92C/198F, probably a few minutes after the thermostat has opened. Your otterstat is set to turn the cooling fans off at 85C/185F. So long as the thermostat is remaining open, which is typical in warm ambient temps once the engine has warmed up, you're fans are always going to be running and never turn off with that setup, as the turn off temp on the otterstat is below the thermostat temp. As Dave mentioned above, this is going to be especially true at idle or slow moving speeds on days with a high ambient temps. Do you notice any difference in operation when moving at sufficient speed?

As to why it worked before and cycled the fans, it could be due to ambient temps and/or discrepancies with the otterstat, as Ed said, they all have a certain range of variability. Could also be that for some reason, the new radiator isn't cooling as efficiently as the old one was.

To confirm exact otterstat trigger temps, you can test it outside the car with a pot of hot water and a thermometer.

You could also put your old otterstat back in and see what happens - that way you'll know if the new one is just biased to the low end in its variability.

Best luck :thumbup:

[skynet]

Wow, thanks for your quick reply! I'll think about which way to follow - I don't want to "boil" the engine once again (happened before), but don't want to overcool it either. I'm gonna run sone tests and measure temps again first. Thanks again!

[NightFlyer]

Wow, thanks for your quick reply! I'll think about which way to follow - I don't want to "boil" the engine once again (happened before), but don't want to overcool it either. I'm gonna run sone tests and measure temps again first. Thanks again!

I edited my comment after I thought about it some more - check out the edit for some better suggestions :smile:

[Ron]

The thermostat should open at 85°-89°C (185°-192°F) [See A:01:01] Upper end makes K-Jet behave a bit better during warm up...

Normally, the system expects the fans to be "activated when the engine coolant temperature exceeds 97°C (206°F) and deactivated at 91 °C" (195°R). [See C:14:01]
Sounds like ya need an otterstat to me...

[skynet]

I might try the higher range (factory) otterstat but now I have a laser thermometer so I'll be able to test during the weekend. The only problem is the weather not being hot enough... ;)