Radiator Fans Not Staying On

[KJT]

2005 2.8 CRD The fans kick in after about a minute of starting the engine (air con switched on)then run for about 10 seconds then stop. They cycle like that but they will not run continuously. This issue is causing an overheating issue when the weather is very hot (which it is right now). In cooler temps with air con switched off, the radiator seems to air cool sufficiently to enable me to use the car but not if the weather warns up at all. Edited May 8, 2018 by KJT

[bignev]

Sounds quite like another blocked rad, and maybe part of the system too.

 

But do try flushing the coolant through first, hose in expansion bottle and bottom hose loosened so it can pour out, check the colour and state of it too, obviously.

[KJT]

Thanks for your reply. A blockage? That seems odd as the rad is only a few months old and I have a consistent interior temp through the blowers. It doesn't overheat on idle of blowers set fairly warm. Not saying your idea is incorrect but I'm not sure I can see how that would be the case. Can you possibly add some reasons why you think it may be the rad please? Thanks

[bignev]

Because you didn't say you had a new rad.    And it's more than a little common occurance on here.

 

The fans run to put air over the Air Con evaporator coil at the front, and correctly they don't necessarily stay on full time, depending on air temps. So they will run more or less straight away 

 

And most diesels won't get up to temp for ages on idle let alone overheat, none of mine ever have, but my GV is a petrol. But they will get warmer faster with the AC on as it puts warmer air from the evaporator coil over the rad.

 

But if it's getting too hot then it isn't rejecting the heat somehow.

So either the big thing at the front that gets cooled by the airflow by the car moving or fans isn't able to do its job,

 

or there is a lack of flow of water through it, coming back to either a blockage in the cooling system (in your case front biased not interior) which is why I suggested flushing it clear,

 

or a blocked rad (not if it's new),

 

or an air lock which I believe on the diesels isn't likely they vent to the expansion bottle,

 

or - very very very rare but one of our guys has had it - the thermostat stuck shut, they are designed to fail open which is why in winter they never get above 1/4 on the temp gauge, but, and this is a guess, if yours is stuck shut, then in winter or cooler weather when you are using the heaters you could be possibly taking just enough heat to balance the engine temp.

 

or the water pump not performing.

 

When I got ours, the impeller was knackered on it, so good job I had already decided to fit a new one !!!

 

So then - if your fans only come on for a short time, assuming (oh very dangerous with these) that other things are doing what they should, that would mean the temp at the sensor is dropping quickly, meaning not much water passing through the rad so it is able to be cooled off quickly.

 

OK diesel guys - your turn for input fellas 

Edited May 8, 2018 by bignev

[KJT]

I appreciate your detailed reply. Can anyone tell me where the water temp sensor is located in the engine bay of the 2.8 diesel? (and is this related to the temp sensor on the dash?) And is there a test I can perform to check if the water pump is working properly or not? It was changed for a new one upon sale (about 3 years ago) along with the cam belt so I'm hoping it's still ok...

I believe the way to test the thermostat is to run the engine up to normal running temp and see if the water level in the expansion tank drops. Would that be about right?

Edited May 8, 2018 by KJT

[andyb2000]

Hm, all of the info above to me seems more related to coolant temperature, but the radiator fans not running continuously I think may be something different.

 

When you have the engine running and switch the air con on the fans should come on and run continuously whilst the a/c is active, so if you force that (switch to manual, set low temperature and hit the a/c snowflake symbol) if the fans go on then switch straight back off my suspicion is that they're not spinning freely so the ECU is detecting this and cutting them so they don't burn out/damage, etc.

 

So, with battery disconnected (to make sure fans don't start whilst playing!) see if you can spin each fan, they should spin freely and shouldn't stop the moment you stop spinning. If either one does then disconnect that fan, reconnect the battery and try the test again with the engine and a/c, see if it still cuts out.

 

To me, this is the ECU cutting power to the fans for some reason, so i'd go electrical at first, check both relays (The two left-most relays on the front of the engine bay on the crossbeam) and if needed swap them for known good relays to test.

[KJT]

That's great bud. I'll give it a go tomorrow. By any chance do you know what the other relays are on that slam panel and what equipment they service? I've been trying to find this out for ages!

[KJT]

The fan relays all check out as good after testing. I had a sudden power drain from a bad 70amp relay over the last 3 days, but now I've replaced it, there are no further battery drain issues so I'm back onto my fan problem!

The fans spin but hand but only for a second or 2. Is that normal? They don't feel hard to turn at all but they don't keep spinning. I hope that makes sense...

[recepomac]

hi bende voyager 2.5 crd manuel got the car very hotter I changed the thermostat circulation pump the problem is not solved !!
Responsibility: cooling fan is single speed, double speed

[andyb2000]

OK, so we know relays are eliminated.

That sounds about right for them spinning, so at least they're free moving. I suppose next part is coolant temperature sensor which you rightly queried, though I'm not 100% on location, will take a look when I'm home at the wiring diagram, however what does the dial in the car show, if that reads normal I'd not expect the temperature sensor to be at fault.

 

I guess next steps depending on how adventurous you are! Personally (being more inclined to electrical!) I'd be getting a couple of wires from a battery, disconnect one radiator fan connector and feed 12v straight into the fan terminal, get it to spin and see if it keeps spinning. That way you know for sure if it is the fan itself or not.

(Usual caveats apply, don't cross the wires, etc, as car battery can pack quite a punch/spark!)

The other alternative to that is to use a multimeter and read what voltage is being supplied to the fans, if its constant 12v then you know it's the fan itself, if it's 12v then down to 0 then its the ECU cutting power to the fans for some reason.

 

Unfortunately it's a step-by-step process this one. I'm hoping it's not the ECU cutting the power as that could be all sorts of reasons.

[andyb2000]

Coolant temperature sensor location
 

 
From memory this is a 2-pin sensor (You'll soon notice when you take the connector off), if that's the case then it'll be a resistance type varying the resistance depending on temperature so you could do a simple test of check it when engine stone cold, then check it again after a drive around to get up to temperature, see what varyance is, but I'd not know the thresholds without doing more digging I'm afraid.
 

[bignev]

Ah ok then - a correction to my statement in #4 - if the temp sensor is on the block then the comments regarding the water cooling off too quickly in the rad are wrong, they're valid if the sensor for the fans was on the rad!

 

My apologies on that one.

 

So a bit more detail from you KJT - can you drive it in warm weather as long as you're not stuck in traffic? So the car moving creates enough airflow for cooling? So basically normal operation.

[KJT]

If its not a hot day then yes I can drive it around even with the interior heater switched off because there is enough air cooling going on as I drive. If I then place a demand on the system like air con, or heavy traffic, it starts to get too hot on the temp gauge on the dash. On an average day I like the interior reasonably warm and cosy so the heater is on - in this scenario, the temp gauge never goes above half way even in traffic. The air con stays really cold though when I do try to use it regardless of the engine runing hot, so that's got me a little stumped as I'd have thought air con wouldn't work properly if the rad fans are not spinning.

My temp gauge appears to work normally (I've known/owned the car for several years) and I had ordered a temp sensor just in case, but wondered if there was test I could perform on the original sensor first (like has been mentioned above). Will have to try that. I remember years ago just earthing the temp sender unit on a car and watching the gauge got to max in order to test it, but I'm not having any issues with accuracy at the gauge unfortunately.

I'll have to try the 12v power test directly at the fans and see what's what with that.

 

I'm hoping the ECU isn't playing up....