Mystery Coolant Loss ??

[TheMadhatter]

I have two issues with my 02 130TDI sport.

I had a shock today when driving along, the STOP sign came up on the dash followed by check coolant level. I stopped checked it and yes it was down to the min mark.

Now I have had a very slow loss of coolant from the car since I got it two years ago. By slow I mean 250ml of G12 has to be added every 6~12 months or so.

I can smell warm coolant in the engine bay but can't see it leaking from anywhere. I topped it up with water and then went for a test drive and it stayed filled up. Everything ran fine no issues. I last checked the coolant level about 5 weeks ago and it was just below the max level. I have done about 1300miles of mixed driving since then.

I have one other issue which I was going to get checked at it's next service. Occasionally the glow plug light seems to do the following.

1)Very cold day, goes out immediately and the engine runs ruff for a few seconds.
2)Engine hot, for example stopped at a service station on motor way, glow plug light stays on for 10secs, start engine goes to ~1600 rpm then settles immediately to idle
3)Pull up to a set of lights and the revs either stay at 1200rpm when lifting off or, they pick up from idle (800) then stay there for a few seconds and drop down again.

Number 3 happens very rarely , 1 and 2 are more common but we are not talking every time here.

There are no obvious signs of distress to the engine. The oil and coolant are both the colours they are supposed to be, no smoke coming from exhaust ,except when it does no.1 but that clears after a few seconds. Engine pulls like a train and my fuel economy is good all though saying that I seem to get 3-5 mpg less out of it on a long run than when I first had it but I put this down to a change of tyres and exhaust.

Anyone got any ideas where to go looking for the coolant leak ? and is the starting issue the temprature sensor problem I have seen mentioned a few times on this forum ?

Thanks for any help

[cazyp]

Coolant leak is no doubt the bottom corner of the radiator corroded. Very common. Never seems to leave 'leak' marks due to the undertray. The fix is a new rad.

Your other problems sound like coolant temperature sensor (rather than temp' sender which is a different part!) although you could have a fualty glow plug - best get a vagcom scan done really.

Oh and welcome to the forum! - don't forget to post updates if fixes worked etc..
HTH.

[TheMadhatter]

Which side ? I had a good look around the bottom edge with the inlet pipe which I could see, and did not see much. It's a bit wet out there to go taking the under tray off and looking for a water leak lol.

[cazyp]

Mine was leaking from the O/S or the left lower corner as you look at the car. Down near the turbo. Very hard to see the patch of corrosion/leak with the bumper on but it'll be there...!

[ando l]

check the pipe that runs from the back of the head small pipe runs underfuel pump /vacuum pump mine perished coolant leaks onto cat so get smell

[Col]

The radiator rots at both bottom corners where it squishes into a foam seal which is on the front panel (lock carrier).

Almost undectable until the rad is off, especially the volume of coolant you are loosing.

See piccies below taken when I changed mine on my old 2002 Passat, both corners had gone.

http://img.photobucket.com/albums/v602/colin__/Passat/P7180077.jpg

http://img.photobucket.com/albums/v602/colin__/Passat/P7180078.jpg

As for the glowplug symbol and erratic idling / revving, change the coolant temp sender. Very common problem. Note the sender is duel output so whilst the temp gauge may be fine, the data sent to the ecu could be duff causing the ecu to increase fuelling and or treat the engine as cold when it is hot.

[TheMadhatter]

I have been monitoring the coolant level for the last few days and it has not gone down by a perceptable amount. I can smell hot coolant just after I stop though. It's getting serviced soon will get the independent to investigate at the moment I can't see anything.

Can you get anysort of UV dye to put in the coolant to spot leaks like you do with the aircon ??

[martin1810]

If it only leaks a little the heat will evaporate the water so you won't see much. Shine a bright light onto the radiator at the bottom corners and they will almost certainly look wet.

[00mrmark00]

My temp guage has not worked for donkeys. Hence, I reg have to check the coolant level. That never moves buy the way form one service until the next.

I was told it was a replacement dash pod to fix my issue, but not at £600... I'll keep checking it manually.

Good luck with the rad...

[cazyp]

I have been monitoring the coolant level for the last few days and it has not gone down by a perceptable amount. I can smell hot coolant just after I stop though. It's getting serviced soon will get the independent to investigate at the moment I can't see anything.

Can you get anysort of UV dye to put in the coolant to spot leaks like you do with the aircon ??

Mine only lost about 5mm every 1000 or so miles to start with. No to the dye.. And no point really as it'll be those lower corners.