Radiator water loss scavenger fan not working

[Faribaandme]

After replacing water hose I noticed that in traffic jams I can see steam come up from the bonnet. I look at the water temperature gage and it is still on cool I look at the temperature for the engine at that is at normal running temperature also the scavenger fan did not turn on. I think or thought that the water is coming out of the header tank as the water rises .......... perhaps not because temperature still cool.

We felt perhaps we did not to the best job in bleeding the radiator so the wife and I followed the 3 youtube videos on bleeding the radiator again and felt we did the job.

I turned on the air conditioning and noticed the radiator fan come on (I think) as I could feel the air blowing and hear the noise but NOT the scavenger fan.

No white smoke no gunk in oil and at no time has the engine been overheated. Van runs great and was running great before changing the hose.

Took van for drive no traffic problems van cooled. When I went back to van noticed header tank low in fact low coolant alarm went off before starting van.

I checked all the fuses under the bonnet for the scavenger fan they all seem to be ok

Order of things to do:

Get scavenger fan going I understand a sensor 2 PIN 95-03 maybe the cause I read on the forum that it's on the drivers side next to the hand brake. Do you know where a photo of this is not a diagram? I understand to test it if I take the sensor out and put it in hot water that should turn on the scavenger fan?

When scavenger fan is fixed replaced etc get the system pressurised as perhaps leak somewhere.

I saw this on the internet.

then it's either:

• thermostat not working
• failed/leaking water pump
• heater matrix leak
• some other hose leaking somewhere (turbos?)
• top tank cap - try replacing with 1.3 bar cap
• head gasket/s

I hope you can help
Confused Robert.

[g8dhe]

The scavenger fan only comes on when it is VERY hot around the engine, it cools the engine bay itself, if you unplug the sensor mounted by the handbrake then the fan should come on I believe. So you can test its operation that way.

Might be worth checking that you don't have a leak from the radiator itself, quite a common problem, the plastic top looses contact with the metal body and water will drip/squirt out. Take off the air scoop over the radiators and check the coolant radiator behind the air con radiator for any signs of leaking, you can run the engine quite happily as the air scoop is only for the cabin air system.

[JoeC]

By the handbrake under the cowling is a plastic temp sensor that is used by the scav fan. Put this out and run a hot hair drier over it to see if the scav fan comes on or not. May help to find the root cause.

[Gasy]

Just short the cables out to the sensor to bring the scavenger fan on

The sensor is in the middle of the pic
You can see where I have teed extra cables in which go to a switch next to me handbrake so I can bring the scavenger fan on when bongo gets hot

[Bob]

Useful pic, thanks.

[Northern Bongolow]

try just topping up the header tank to the correct level marked on the front of the tank when the coolant/engine is cold. you may not have got every last bit of air out when bleeding it, this is quite common to have to top up after bleeding for the first few times after learning to bleed em, with practice you do get better at it.

i wouldnt worry about the scavenger fan too much, this alone wont stop an out of temperature control bongo from boiling up as the front fans do this, the scavenger fan is only there to cool the occupants bums when things are getting a little warm. ive messed with bongos for over 8 years and have never seen a scavenger fan trigger on or off by itself in normal use.

[Faribaandme]

you people are wonderful ............ great advice i will check it out today.

[mikeWalsall]

Mine is a V6 .. I leave my air con on full time .. very rarely turn it off even in the winter (it's A/C not a cold air devise) so I tend to have a radiator fan on all the time ..

The only time I have noticed my scavenger fan kick in was when leaving the engine running while waiting inside the MOT station for half an hour..

[mikeonb4c]

I found fitting an over-ride to the scavenger fan helped keep bums in the car much cooler than the factory sensor alone, which seems more concerned with keeping the engine bay components from getting too hot. I only started using the over-ride switch intelligently once I fitted a TM2 engine block alarm which allowed me to see when it might be time to switch on the over-ride fan on. But working together, they provide a very effective remedy. Agree though that scavenger fan alone will not solve overheating in an engine with compromised coolant system, though it will help just a little perhaps.

[Faribaandme]

Followed instructions from "Northern Bongolow" topped it up to correct level and "g8dhe" took off air scoop off and left it off to test.

Started van no white smoke. Took van for run 5 miles approx 15 mins stopped at vets checked bottom hose still cold no leak water at correct level. 15 mins stopped a Aldi bottom hose warm no leak water at correct level. 15 mins stopped at mothers no leak water at correct level TM-4 engine block alarm both temperatures gages low. 15 mins home. Next morning checked water level ..... perfect.

Thoughts:
I remember when the steam came out from under the bonnet just after I bled the radiator and just started using the heater. Need to take a run long enough for the thermostat to kick in with heater on.

Wild guess: Perhaps was air in system caused radiator to overheat causing steam or ......... leak in heater core?


Followed instructions from "Gasy" GREAT photo I did short out the cables and the scavenger fan came on.
Thank you "mikeWalsall" I always run the air if I need to demist windows.
Thank you "mikeonb4c" I will do the same if it helps on that hot, hot, hot day.
Also Thank you "JoeC".

Don't use van much as live in London "parking, traffic, people problem" that's why we own a Bongo to get away; however will let you know.

Thanks to all!

[mikeonb4c]

Glad things seem to be sorted.

[Bob]

Agrred, well done.