[Farhan]

Hi all, Im currently trying to tackle a few problems on my car, Yesterday my coolant light came on saying it was low. I checked and it was indeed below minimum which was surprising as it was topped up correctly not long after the flywheel was replaced. I do remember when the gearbox was removed alot of coolant came out buy my mechanic did top this up. I have checked thoroughly and no physical sign of a leak on the driveway. Engine oil checked and i can see no contamination at all levels all seem fine.

I retopped it up with G13 mixed with water to the correct level and it seems to be holding now, It has dropped a tiny bit but is still near the maximum marker when cold. Could this be air in the system when it leaked out?

Finally my air con is still not blowing out fully cold, Scanned on VCDS and the compressor runs, Air-Con has been gassed and the pressure switch was changed. It literally takes around 20 minutes of driving to start blowing cold. Even then it needs to be on full to blow cold air for a noticeable difference, I feel as though its not pumping air through the vents strong enough.

Both fans run when the air con is on but my main concern here is with my climatronic turned off i have never noticed the fans run! The engine bay is always extremely hot which is worrying me (Temperature needle has never gone over half way however. Im just wondering do neither fans run when the climatronic is turned off? Also how can i test that the fans work when the climatronic is off as even in this blistering heat with the engine being run for an hour i have never noticed them come on unless i turn on the A/C.

For ref any help would be appreciated, i have access to a VCDS so i can run some checks on that if need be.

 

[cuprabob]

The fans run on low speed when the air con is on and don't run at all when the air con is off unless the coolant temperature reaches around 100 degrees, in which case they start running, irrespecive if the air con is on or off.

With the climatronic on "auto" the air con is off unless "Econ" is selected in which case the air con is off.

With climatronic "off" air con is off.

Sounds as if your car is doing what it should.

Always check coolant level when car is stone cold like first thing in the morning.

If you do notice it dropping, get it pressure tested for leaks.

 

[CorradoR32]

Coolant loss - check the engine carefully for baked-on pink crusty leak deposits. Old favourites are the thermostat housing, 'crack pipe', aux pump and main pump. The R has a fairly complex and convoluted coolant system, so topped up water can drop down on the expansion tank but it should level out within 3 or 4 journeys.

If it's still going down and the head gasket is fine and no engine leaks, then the only place it can be going is out of a broken heater matrix. Head gasket and matrix failures are very rare on Rs though. On a standard R, the HG will only fail if the engine overheats enough to warp the head.

Ignore the temp gauge. It still sits at 90 when actual temp is 105! Use VCDS for the real measurement.

As above, the fans are 2 speed and come on at around 100 for speed 1 and 110ish for speed 2. The MK5 ecu also has a fan / aux pump control, unlike the MK4 which is all done by the fan controller. If the MK5 has a 3 pin sender in the radiator, you can unplug it and bridge the connections to test the fans.

As for the AC, check the cabin temperature with VCDS (auto vac module) and see how long it takes to drop down to 16 deg. As said before, I suspect your condenser has lost it's efficiency / pressure or possibly because your fans aren't cooling it.

 

[cuprabob]

Just for completeness, a number of early MK5 R32s suffered from porous blocks which manifests itself as pinhole to the outside world. Thankfully it's very rare but I was one of the unfortunate people to suffer from it. VW came good for me and,replaced the engine FOC

As I said it is very rare and any coolant loss is likely to be due to one of the above described by CorradoR32

 

[Farhan]

Coolant loss - check the engine carefully for baked-on pink crusty leak deposits. Old favourites are the thermostat housing, 'crack pipe', aux pump and main pump. The R has a fairly complex and convoluted coolant system, so topped up water can drop down on the expansion tank but it should level out within 3 or 4 journeys.

Thanks, I will have a look at the following. If im correct the thermostat housing seats the thermostat this would usually indicate a DTC would it not if the thermostat was not kicking in? Aux pump would be the water pump i will also check this, i am sure this would be due for replacement now on my car but i will double check if it was already done. What is the main pump? I have topped up the expansion tank for the moment so i will now constantly monitor this over the next few days.

If it's still going down and the head gasket is fine and no engine leaks, then the only place it can be going is out of a broken heater matrix. Head gasket and matrix failures are very rare on Rs though. On a standard R, the HG will only fail if the engine overheats enough to warp the head.

I checked the passenger floorwell for any dampness but i did not notice anything at all so hopefully im fine on this front, I can confirm the heating works as i have constantly checked this. Concerned on the gasket front whilst i have never seen any contamination in either the oil or coolant i do feel the engine does get extremely hot after driving which makes me wonder why the fans are not kicking in. I will double check the temperature tomorrow using VCDS.

Ignore the temp gauge. It still sits at 90 when actual temp is 105! Use VCDS for the real measurement.

As above, the fans are 2 speed and come on at around 100 for speed 1 and 110ish for speed 2. The MK5 ecu also has a fan / aux pump control, unlike the MK4 which is all done by the fan controller. If the MK5 has a 3 pin sender in the radiator, you can unplug it and bridge the connections to test the fans.

Just wondering again as this is a controller would this not throw a DTC if it was malfunctioning that would help eliminate any problem areas on the fan/aux pump control. I could try the fan test the only thing im wondering is im sure the fans do work as they run perfectly fine when the aircon is switched on, Both fans can be physically seen running.

As for the AC, check the cabin temperature with VCDS (auto vac module) and see how long it takes to drop down to 16 deg. As said before, I suspect your condenser has lost it's efficiency / pressure or possibly because your fans aren't cooling it.

My guess is now also on the condenser as i can physically see it has taken a battering from stone chips, when i removed my front grill i did remove a lot of wood kind of debris from the condenser, it is quite possible it is loosing gas hence the low pressure and long cooling up time. Sorry to sound very inexperienced but when the fans spin are these needed to keep the condenser cool? Just trying to relate the two but the condenser would be on when the air con is switched on? The moment my air con is running the fans also run so surely the fans would cool the condenser that is another area which i can mark out.

Thank you for your advice, Will report back my findings and hopefully have my mechanic have a good look into this over the weekend

 

[Farhan]

Just for completeness, a number of early MK5 R32s suffered from porous blocks which manifests itself as pinhole to the outside world. Thankfully it's very rare but I was one of the unfortunate people to suffer from it. VW came good for me and,replaced the engine FOC

As I said it is very rare and any coolant loss is likely to be due to one of the above described by CorradoR32

I did have a read of some of your posts regarding this hopefully it is not this, Where there any obvious symptoms in running which you noticed with the porous block? Also at the time was the car under warranty when the engine was replaced?

 

[cuprabob]

The only symptom was that after 4 years / 67k miles the car started losing coolant, when up until that time the coolant level never varied.

The car was in the last few days of the VW Extended Warranty however the fact I bought the car from my local dealer and they were the only people ever to work on the car meamt they supported my case with VW. Although it was quite stressful at the time, as you would imagine, it was resolvedvery quickly and was only without the car for around 10 days.

I'll be honest, if VW had decided not to pick up the tab, I would have traded the car in and that would have been the last VW I would ever have owned

As I said, don't worry as it's very rare.

 

[CorradoR32]

Thank you for your advice, Will report back my findings and hopefully have my mechanic have a good look into this over the weekend

No worries.

The thermostat is mechanical (a 100 year old design, lol) and isn't monitored by the ECU. Only the water temp is via the green 4 pin sender in the 'stat housing. The 'stat housing and associated plastics can warp with age and leaks can occur. I always replace them as a matter of course when doing clutches and chains etc. The aux pump is at the front of the block, next to the alternator. The main pump is on the driver's side of the engine and belt driven by the crank. Aux pump - £100. Main pump - ~ £40. If any of these parts are leaking, you'll soon see the signs!

The big engine does get hot under the collar this time of year. VW tested these cars in Dubai (can hit 50 deg!!), so I wouldn't be too concerned by the under bonnet temps unless you can cook an egg on the intake! Bear in mind the heatsoak if you are lifting the bonnet after 5 mins. It will be a little cooler if you lift the hood immediately after stopping.

The fan controller isn't monitored for fan operation unfortunately. So long as the a/c and ecu can see it electrically, it's happy. That was always an issue with MK4s with the blown low speed fan resistors. The engine and a/c would carry on regardless none the wiser! Given how critical cooling is for the R, it's a curious ommission! Sounds like they work though but check they come on with the a/c off as well.

Yeah the condenser needs to be kept cool by the fans or the a/c will struggle to reach the target temperature. Similarly, you shouldn't use the a/c on full cold with the windows open. I think you need to get your a/c dye tested. They pump a flourescent liquid into it, which reveals any leaks.

Keep us posted!

 

[Farhan]

No worries.

The thermostat is mechanical (a 100 year old design, lol) and isn't monitored by the ECU. Only the water temp is via the green 4 pin sender in the 'stat housing. The 'stat housing and associated plastics can warp with age and leaks can occur. I always replace them as a matter of course when doing clutches and chains etc. The aux pump is at the front of the block, next to the alternator. The main pump is on the driver's side of the engine and belt driven by the crank. Aux pump - £100. Main pump - ~ £40. If any of these parts are leaking, you'll soon see the signs!

The big engine does get hot under the collar this time of year. VW tested these cars in Dubai (can hit 50 deg!!), so I wouldn't be too concerned by the under bonnet temps unless you can cook an egg on the intake! Bear in mind the heatsoak if you are lifting the bonnet after 5 mins. It will be a little cooler if you lift the hood immediately after stopping.

The fan controller isn't monitored for fan operation unfortunately. So long as the a/c and ecu can see it electrically, it's happy. That was always an issue with MK4s with the blown low speed fan resistors. The engine and a/c would carry on regardless none the wiser! Given how critical cooling is for the R, it's a curious ommission! Sounds like they work though but check they come on with the a/c off as well.

Yeah the condenser needs to be kept cool by the fans or the a/c will struggle to reach the target temperature. Similarly, you shouldn't use the a/c on full cold with the windows open. I think you need to get your a/c dye tested. They pump a flourescent liquid into it, which reveals any leaks.

Keep us posted!

Thanks again,

I am slightly concerned as the fans have never turned on without the A/C im thinking of testing these somehow? Do you have any suggestions. The car hasnt once overheated and it has been run for hours on end but i have never noticed the fans coming on themselves without the AC running. I have read alot of threads but they are for the MK4 im a bit confused as to what i should check for the MK5 fans to see if they run.

I have a VCDS but i am a bit amateur at using it so would need a bit of advice on what scans or tests i should run to see if the fans run as they should.

I topped up my coolant and i havent noticed it drastically falling, Again i have been monitoring my oils as i always do and all seems clear on that front. I will at some point get it to my mechanic to have a proper look under to see if we can spot any areas which you mentioned for leaks. oii

 

[Farhan]

Ok small update on this, I can confirm my fans do work! Popped the bonnet today to check for something else and with the HVAC all turned off i saw the larger fan spinning as intended

As for the coolant loss, I topped up the coolant since last time and i have noticed it goes down very VERY slowly over the course of a few days. No warning has flashed up again but it does slowly fall below maximum. I am continually checking my oil and i have not noticed any contamination. I have a strong feeling it may be the water pump which could be due for replacement. Will diagnose this further at some point.

 

[cuprabob]

Speaking from experience it's hard not to get paranoid about the coolant level. I found that if I topped it up it would drop slightly over time to a level and remain there. Just remember only to check the level first thing in the morning when the car is stone cold to get consistent readings.

For the low level alarm to activate it has to be around half an inch below minimum.