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Discussion Starter #1
Hi Guys,

This overheating is driving me mad and any help would be greatly appreciated

I have 2008 T5 1.9 84 bhp.

The symptoms are

When idling its okay
When I drive more than say 12 miles it starts to lose coolant via the overflow
When I drive it above at 2500 rpm or higher it virtually empties and the red light comes on (at least that works)
The thing I have noticed is that the fan never seems to come on, even though everything appears to be working. The Engine starts from cold and gradually warms up. bottom hose is cool but the top gets hot and the hoses in and out of the reservoir tank get hot. I take it for a short drive and the bottom hose gets hot, so I think the thermostat is okay. I leave it to idle after the short journey and wait for the fan to come on - but it never does!!!.

It's been to the garage and been returned to say they can't find anything wrong they said they couldn't find any leaks and tested the cylinder head but it was okay - but it still overheats and I constantly have to keep topping it up from below the minimum to minimum or slightly above or to maximum, but it makes no difference.

I have changed the reservoir tank cap - no change
I have changed the Coolant Temperature Sensor - no change
I have changed the Coolant and checked the concentration, it has 2/3 floating balls - no change
I have changed the Cooling Fan Control Unit - no change
I have tested the fan by wiring it directly to the battery and it springs into life - so the fan works - but it's not being told to come on.
I have tested the supply to the Fan Control Unit and that's giving me 12v
I have taken off the ground connections to the chassis and cleaned them back to bare metal and refitted - so the circuit should be good
I have tested every circuit fuse by removing every one in the engine bay and under the ashtray and get good continuity across both blades - I have also double checked the voltages with the engine running and getting roughly 14v on both sides of each fuse. (There are a few fuses that don't have any voltages on either side - so I figure that these are unwired as my model is basic so may not have some of the accessories that some other models may have - but I may be wrong in that assumption).

I am clutching at straws - but I have tried shorting out the radiator thermo switch at the plug end to try and convince the fan control unit that the switch has been closed - but it has made no difference - but I do have a new one on order along with the thermostat, but I am not convinced that either or both of these being replaced will solve the problem, because the bottom hose is hot and I have tried shorting out the plug of the radiator thermos switch.

I know the fan works, but I can't work out why it's not being told to come on

If anyone can help, I would be really grateful - I'm stumped (BTW I'm not a mechanic I'm just trying to fix my ride)
 

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Have the garage pressurised the cooling system?
Also have they checked the operation of the water pump?

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I'm not sure that you can read too much into the fact that the fan does not run. On modern diesels it's quite common to find that they run only in the most extreme conditions. My 2l Kombi fan almost never runs - ambient temps have to be really high for that to happen.

There are a few fuses that don't have any voltages on either side - so I figure that these are unwired as my model is basic so may not have some of the accessories that some other models may have - but I may be wrong in that assumption).
This would be very unusual for a VW of that age. They simply don't fit fuses (or terminals, or wiring) for options that other models have but yours does not. It would be a good idea to use your favourite internet search tool and find a fuse layout for your model/year van. Note that the pre-facelift wiring/fuse layout changed at least half a dozen times prior to 2010, so a "generic" fuse layout won't always help.

If it were mine, I would want to know what checks the garage have made in terms of head gasket testing.
 

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Discussion Starter #4
Have the garage pressurised the cooling system?
Also have they checked the operation of the water pump?

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Thanks for your reply, I don't know what exactly they have done - how do you pressurise the system is it something DIYer could do?

I disconnected the small hose from the top of the reservoir tank and fed it through the open filler cap and ran the engine and I got flow and the flow increased when I revered the engine (got my son to help)

I don't want to hassle the mechanic as his wife is very very poorly (- hence the reason why I tried to fix it myself)
 

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Discussion Starter #5
I'm not sure that you can read too much into the fact that the fan does not run. On modern diesels it's quite common to find that they run only in the most extreme conditions. My 2l Kombi fan almost never runs - ambient temps have to be really high for that to happen.



This would be very unusual for a VW of that age. They simply don't fit fuses (or terminals, or wiring) for options that other models have but yours does not. It would be a good idea to use your favourite internet search tool and find a fuse layout for your model/year van. Note that the pre-facelift wiring/fuse layout changed at least half a dozen times prior to 2010, so a "generic" fuse layout won't always help.

If it were mine, I would want to know what checks the garage have made in terms of head gasket testing.

Thanks for your reply, I would have thought if it was hot enough for the coolant to be forced through the overflow - it should be hot enough for the fan to come on. Im convinced the problem is with the fan. (but very possible I could be proved wrong)

Thanks for the advice on the seemingly spare fuses I will try to get something from the VW dealer unless you could point me in the right direction - I have got the engine code BRR and the year of manufacture would that be all they need?
 

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Discussion Starter #6
I'm not sure that you can read too much into the fact that the fan does not run. On modern diesels it's quite common to find that they run only in the most extreme conditions. My 2l Kombi fan almost never runs - ambient temps have to be really high for that to happen.



This would be very unusual for a VW of that age. They simply don't fit fuses (or terminals, or wiring) for options that other models have but yours does not. It would be a good idea to use your favourite internet search tool and find a fuse layout for your model/year van. Note that the pre-facelift wiring/fuse layout changed at least half a dozen times prior to 2010, so a "generic" fuse layout won't always help.

If it were mine, I would want to know what checks the garage have made in terms of head gasket testing.
sorry missed the head gasket comment - I don't know what exactly the mechanic did - just took it at face value - what would I need to ask?
 

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You can buy pressure testing kits from ebay I'm guessing.
I've had a water pump seem to look ok when at idle and holding revs on and seem to be flowing back the the coolant bottle fine but when it was driven and then warm it was causing the metal shaft part of the water pump to spin inside the plastic impeller of the pump

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Discussion Starter #8
You can buy pressure testing kits from ebay I'm guessing.
I've had a water pump seem to look ok when at idle and holding revs on and seem to be flowing back the the coolant bottle fine but when it was driven and then warm it was causing the metal shaft part of the water pump to spin inside the plastic impeller of the pump

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ah ha - makes sense - I will get one and see what results I get - I don't think the pump has ever been changed and is at 99k now - but will check with the previous garage who changed the timing belt a couple of years ago to see if they changed the pump at the same time - thanks for that
 

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I always change water pumps with cambelts as it's more cost effective at the time rather than if failing after and then changing it all again.
Hope you get it sorted

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Discussion Starter #10
I have just checked the service manual that came with the van would it's very basic and only gives me the dash fuse board it looks pretty rubbish as according to the diagram I've only one fuse in the engine compartment and I know I've got more than that. I've also got 2 number one fuses but only one on the diagram - can't see anything for the radiator except auxiliary heating - who design this for the manual?
 

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I'm not sure that you can read too much into the fact that the fan does not run. On modern diesels it's quite common to find that they run only in the most extreme conditions. My 2l Kombi fan almost never runs - ambient temps have to be really high for that to happen.



This would be very unusual for a VW of that age. They simply don't fit fuses (or terminals, or wiring) for options that other models have but yours does not. It would be a good idea to use your favourite internet search tool and find a fuse layout for your model/year van. Note that the pre-facelift wiring/fuse layout changed at least half a dozen times prior to 2010, so a "generic" fuse layout won't always help.

If it were mine, I would want to know what checks the garage have made in terms of head gasket testing.
"When I drive it above at 2500 rpm or higher it virtually empties and the red light comes on (at least that works)"

Hi... Would that not be indicative of head gasket leak or water jacket integrity breech where water is sucked into the bore at high rpm? Would also manifest itself as bubbles in the header bottle at high revs?
Oil MIGHT be milky also if that is the case.
Just a thought...

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Discussion Starter #12
"When I drive it above at 2500 rpm or higher it virtually empties and the red light comes on (at least that works)"

Hi... Would that not be indicative of head gasket leak or water jacket integrity breech where water is sucked into the bore at high rpm? Would also manifest itself as bubbles in the header bottle at high revs?
Oil MIGHT be milky also if that is the case.
Just a thought...

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Hi thanks for your thoughts much appreciated.

I think the mechanic checked the cylinder head for leaks as you indicate - but he says it came back as okay. Also the coolant doesn't seem to disappear it escapes through the overflow. If I drive it like Miss Daisy and keep the revs below 2000 I generally get away with it or maybe just a little loss but not much. If I drive it hard there is no evidence of smoke from the exhaust that the coolant is escaping through the engine. The Oil appears to be unaffected no scum or milky could to it.

I have just read a thread that appears to be very similar to my problem that seems to point to what you have indicated though and the fault appears to be a faulty cheap gasket BGR, but I have had no work done that would require a replacement gasket and it's been fine for 30k miles until the last 6-8 weeks.

Can I test to see if the coolant is mixing with the oil or exhaust - perhaps you could point me in the right direction. - Again many thanks for your reply
 

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Discussion Starter #14
I don't think so - I checked the bottom hose and it was hot when I drove it for about 30 mins and the radiator fins where hot from top to bottom and left to right - It could be restricted but how would I be able to check that - Or would I need to take it to a radiator garage - any recommendations for Hampshire?

Thanks for your comment BTW much appreciated
 

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Discussion Starter #15
I did put in some Rad Seal at the start of my problems as I thought there may be a small leak somewhere but it made no difference
 

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I'd say head gasket. You can ignore the cooling fan not working once the normal coolant circulation is upset (which it will be if the head gasket is allowing compression gasses to escape into the cooling system) because it won't work properly and anyway they rarely need to be switched on a diesel unless the van has A/C.

If you are getting coolant pumping out of the reservoir on a 1.9 it is quite likely to be head gasket. I would still check/change the thermostat first and check the water pump history but your symptoms are quite common on a 1.9. Both sniff and dye tests for head gasket problems are not infallible. Diesel head gaskets often only leak under load where petrol head gaskets are quite happy to cause the same sort of problems even at idle.
 

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Discussion Starter #18
Thanks so much for your confident diagnosis. I don't think it's been changed when the timing belt was done a couple of years ago - so it seem overdue anyway. would it be worth doing the radiator at the same time in your opinion - or leave it until it needs it?

Thanks again for your reply
 

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Discussion Starter #19
"]f you are getting coolant pumping out of the reservoir on a 1.9 it is quite likely to be head gasket. I would still check/change the thermostat first and check the water pump history but your symptoms are quite common on a 1.9. Both sniff and dye tests for head gasket problems are not infallible. Diesel head gaskets often only leak under load where petrol head gaskets are quite happy to cause the same sort of problems even at idle."

I did have remap done about 18 months ago and have gone from 84 to 156 bhp so is it worth getting a better water pump than the standard one

Once the water pump and thermostat is done - see how it goes for the head gasket? or get it done anyway what's your opinion on replacing the radiator?

Thank you so much for your help - I feel I am getting a clearer picture
 

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Discussion Starter #20
Is changing the water pump a reasonable job for a DIYer to undertake I want to get more involve with the T5 rather than owning it and letting others to the work

Or is it a job for the garage?
 
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