Passat Coolant Issue

[ozrcboy]

Hi all,

Hoping someone might have some insight to offer.

For about a month now my Passat Wagon (B7 MY12 125TDI) has been running at an unusually low temp - the oil temp gauage typically showing 70-80 degrees, versus the more typical range I am used to of 90-100. I put it down to the lower external temperatures (can't say I remember what it normally runs in the cold sub-alpine Canberra/Braidwood areas) and didn't give it much more thought. Most driving is highway cruising at 100-110km/hr.

Last week as I went to leave work I got a low coolant warning. Stopped in at Autopro and bought a G12 equivalent pre-mix to top up. Put about 500mls in to bring it to the top of the mark in reservoir.

For that drive the temperature was 85 or higher IIRC.

I checked it a few days later, and it was down below the min mark again, so I topped up again. Most of the surfaces I measure on aren't perfectly flat. Took another 500mls almost.

Last night leaving a local shindig got the low coolant warning again - vehicle was not parked on an even close to flat surface, drove to a flatish surface and tipped in the remaining dribble of coolant.

This morning coolant is below the min level, but not drastically so (not low coolant warning for example).

Got the torch and tried to have a good look in the engine bay for a leak. The covers on the bottom make it hard for me to get under and look there. However, as best I can see no obvious external leaks, no signs of pink, white or othe residue.

Checked oil - it's about half way through the service cycle so is certainly blackish but this 5w-30 always seems so light and watery to me I can't tell if it is getting anything in it. Oil seemed a little fuller than it should be but could just be a generous top up at last service to allow for slight burn.

Anyway, took the car out onto the road and gave it some hard work to do (lots of accelerating/braking etc) - couldn't get the temp much above 80.

Headed back to home, pulled the dipstick. Slight steam coming from dipstick holder (very slight, possibly just condensation as hot air from dipstick tube hits cold air (8 degrees outside at the time).

So, before I head in to have someone look at this I would like to know if anyone can tell me if this obviously points to one problem or another. Is there an easy test I can do at home on the oil to see if the coolant is getting in there? Are there some easy to reach inspection points I should be checking for?

Any advice appreciated.

Regards,
Oz.

[brad]

It sounds like your thermostat is stuck open & you also have a leak.

[ozrcboy]

I'm sure I could be that *lucky* but it would be an odd coincidence wouldn't it - two cooling related issues occurring at roughly the same time.

[slipshot]

The major issue would appear to be the loss of coolant which is what I would focus on. Assuming you are measuring the levels correctly (sorry, just checking) then I would say that you need to drove the car, park on a flat spot and check the level, then leave it - and then return later check the level before you drive away. If it's the same, check it again when you get home. If it's not look for the leak under the car to get an idea of where the leak is in relation to everything...

You do need to narrow down when it is leaking (over time or when under pressure while driving) and then ascertain where the leak is coming from so you know where to look...

[brad]

I'm sure I could be that *lucky* but it would be an odd coincidence wouldn't it - two cooling related issues occurring at roughly the same time.

I'm thinking the thermostat has been an issue for a while but you only started noticed when your attention was drawn to the coolant loss.

FWIW, My car is taking twice as many km to get the coolant to the magic mark in the current 10c weather than it was 6 weeks back on 15c mornings. Mountains would be worse - you'd be hovering around zero wouldn't you?

As slipshot said, coolant loss is more important. Get a pressure tester onto it, get it up in the air & take the belly pan off. Much easier to find the culprit.

[ozrcboy]

Thanks for your thoughts folks.

Typical temps at driving time are between 0 and 10 (and between -3 and 5 this last week in a cold snap)

Would you take it to a VW dealer, or go straight to a radiator and cooling specialist?

[Hillbilly]

Radiator place Cheaper quicker and more efficient

[brad]

Dealer will want $150 to diagnose. Radiator dude will probably charge nothing.

Recommend you try Canberra VW Centre

[3C4M Guy]

Best not to get distracted by engine oil examinations and theories about stuck thermostats. Main priority is to find the source of the coolant leak.

One way would be to remove the plastic undertray, take the car for a drive to get it warm and the cooling system pressurised then look underneath to find the source of the coolant leak (assuming it's dripping). On the balance of probabilities it may even be a leaking water pump.

[brad]

Have any of you guys ever tried to remove the under-tray & get under & have a look without the aid of (at least) a trolley jack, inspection pit or similar? LOL