Mysterious coolant loss on Roomster 1.6 16V Petrol

[CEG1987]

I have owned my '57 Roomster since new and have now covered 121k without problems.

In the last two months however, the car has been losing coolant after infrequent journeys and I can't pinpoint why.

When the problems began in October, I could cover 300 miles before the coolant in the reservoir dipped below minimum. Then I would have to top it up. In November, this dropped to around 130 miles in-between top-ups. Towards the end of the month, this dropped again to 52 miles after two journeys. During this time, there were intermittent puddles of water gathering on the catch plate beneath the radiator. 

Thankfully, while the radiator felt hot during these times, the car never overheated nor boiled its remaining coolant. 

I checked this out at a VW Group garage, thinking the radiator fan was not working. I was told that the radiator needed replacing and was quoted £300+ for the work. My local garage, who are quite good for a non-Skoda specialist, quoted me less. They took the car in, told me the radiator seemed fine but was leaking due to the Coolant Relay Switch on the side of the radiator coming loose. Having tightened this up and ran the car at 2000rpm for an hour, no loss was reported. However, I was advised to keep an eye on it. 

Having taken the car back and covered a further 25 miles across three journeys, I am still experiencing coolant loss but the puddles on the catch plate are no longer there. 

The oil, which was changed 1200 miles ago, is not milky white but very dark brown. The oil filler cap has no signs of condensation, but also has very dark brown oil residue. Either way, this doesn't seem out of the ordinary. 

There is no sign of oil in the coolant, nor any obvious change in behaviour with the engine or power. 

There are no obvious signs of leaking hoses. 

 

The car is going back to the garage in three days for further inspection.
At worst, I fear head gasket failure. In which case, I feel it wise to ask for a compression test. Otherwise, I am stumped. 

 

I realise this isn't much to go by, but would anyone have any ideas what this could be? And how pricey it could be to fix?
 

[Breezy_Pete]

Check for residual pressure in the expansion tank by opening the cap first thing in the morning (before starting the engine), and listening for a hiss of escaping gas.  Let us know whether or not you hear this.

[CEG1987]

Check for residual pressure in the expansion tank by opening the cap first thing in the morning (before starting the engine), and listening for a hiss of escaping gas.  Let us know whether or not you hear this.

 

Thanks.

I did in fact check this today without running the engine at all. There was no hissing, or change in level, though the cap was tougher to remove and replace than when the engine has run (my guess is expansion of the material under any heat?).

 

There has been hissing in previous cap removals, right after I have had to stop the engine to top up with coolant. But not when the engine was cold. 

Edited 3 January, 2017 by CEG1987

[CEG1987]

UPDATE: Things are very confusing now… 

I have since had a sniff test (December 2016) and confirmed this was okay. I had hoped the head gasket was fine and that my troubles were now over. 
However, I still ended up having to top it up by about a third of a litre every 200 miles. 

Having had a pressure test on the cooling system, there are no leaks. My third garage in three months has told me the following:
-All a sniff test does is tell you weather you have compression in the cylinders. It doesn't tell you if you if water is coming in. 
-There's no way of confirming if the head gasket has gone unless the head is removed. By which time, the gasket is ruined and needs replacing anyway. 

 

BUT, here's the really weird thing…
Yesterday morning when the car was cold, the expansion tank was reading halfway between minimum and maximum (this time, there WAS a small hiss when removing the cap when the engine was cold).
Today when the car was cold, having covered six miles since the coolant pressure test, the expansion tank is now reading half an inch ABOVE maximum. I have since covered 10 miles and left the engine to cool down, it is still reading above maximum. 

My question now is, does a pressure test clear out any air bubbles that might be in the system? If so, could that have been the problem?
It's either that, or £450 to skim the head and replace the head gasket. 

[KenONeill]

Wrong!! The pressure in the cylinders tends to be above the cooling system (particularly at the top of the power stroke). Assuming a spark ignition engine with a 9:1 CR, and not allowing for the expansion of the burning fuel, you have 9*15 = 135PSI relative in the combustion chambers, and only 15PSI or so in the cooling jacket so that's a fair old pressure forcing gas from cylinder(s) into the coolant (which is why a sniff test works).

[Breezy_Pete]

4 hours ago, CEG1987 said:

...-There's no way of confirming if the head gasket has gone unless the head is removed.

 

Not true at all.  One of the most compelling demonstrations of coolant getting into cylinders is to remove a spark plug, shine a bright little torch down the hole and see if it looks wet on top of any of the pistons.

If it does, sample the fluid with a rag on a stick, if it smells/looks/tastes (least favoured option) like coolant, your headgasket is leaking past the fire-ring of that cylinder. Easy.

[CEG1987]

Latest:

Turns out, after a thorough inspection from someone whose taken chain-driven VW group engines apart, it's just a leaking water pump. 

It would explain why it's only been losing so little across so many miles. I kept thinking if the head gasket had gone a while ago, then it would be losing a lot more in fewer miles. 

 

[Robshaw]

Does the car have any other symptoms? Trouble starting? Rough Idle? Puddle under the car? Or Smoke?

 

I had the same random issue but had none of the above 'common issues' with my MK7 Golf GTD. VW have done the following to try and correct the issue:

- Replaced the waterpump & cambelt

- Pressure Test the car

- Drained and refilled the coolant

 

It's going back in for a new EGR next..... They are 100% certain the head is fine.

 

Edit: Would of helped if I read the last post. Glad you've got it sorted.

 

Edited 8 February, 2017 by Robshaw