Hello everybody,

Looking for some help and advice on the following:

I own a Skoda Superb MK2 2.0 TDI 140hp. So far it has done a little bit over flawless 213k kilometers. I've done nothing but regular services and I should mention that before 2k kilometers a regular service was done (new belt, water pump etc...). However, last weekend the coolant sensor started beeping and when I popped the hood I had something to see. The expansion (coolant) tank was EMPTY and boiling at the same time. I left the engine to cool down for a couple of hours and when I checked back, the coolant was back to normal again?

I drove down to the regular workshop and had mechanics check everything for leaks and all, and guess what? No leaks whatsoever. So they suggested CO2 test which showed positive, indicating a blown head gasket. Also, they checked EGR cooler as well and found no leaks. 

 

The complete repair which includes a list of things besides changing the gasket and repairing the head would cost me around 700 euros. 

My concern is what if it isn't head gasket?

 

Is CO2 test enough to tell?

 

Are there any other ways of validating the blown head gasket before removing the cylinder head? 

 

Last question: how reliable can the replacement of the head gasket be for the future? Will it have higher chances of occurring again? 

P.S.

No overheating whatsoever. The engine runs at optimal temperature. The loss of coolant occurred around 5 times so far in the last 10 days. 

 

 

Thank you very much for your time! 

If I had the indicator fluid turn from blue to yellow in my kit, I would be confident either the gasket has gone, the head is cracked or warped, a head bolt has broken or head to block sealing surface is warped, whichever it is, it is causing combustion gas to get into the cooling system.

I don't know in your case, but when the cooling system gets pressurised by the combustion gasses, the coolant hoses expand causing the level to drop in the expansion tank. When you let the pressure out, the hoses return to their normal diameter and the level goes back up. You will know when it is really bad as when starting the engine with the expansion cap off, the coolant will be blown out of the tank.

One other thing to bear in mind with overheating is something else could have caused the gasket to blow/head to warp and it is a result of something like a water pump impeller spinning on its shaft.

When idling or driving slowly at low revs it won't overheat, once the engine speed rises and demanding more flow, the impeller can no longer be driven by the spinning shaft and the engine will overheat, when the revs slow down, the impeller grips the shaft again and cooling is restored.  If this goes on for too long it can damage the gasket etc.  That is why I always change the water pump when I change my cars cambelt.

So you/the garage need to rule out other causes or the same could happen again. The head and block will need to be checked with a straight edge and machined if out of spec. Lots of garages get the heads machined anyway which is fine, but there is a limit to the amount of material that can be removed, so skimming it when it is dead flat anyway reduces the amount you can take off next time when it really needs it. 

If its too badly warped, it will need replacing, a different thickness gasket is usually needed to compensate for the change in compression.

 

Edited 2 July, 20197 yr by 3T51704x4

Thank you for your answer.

As I said, the water pump along with the belt is replaced 2 months ago and the car is currently not overheating at all. I literally tested it by driving at high speeds for 2-3 hours nonstop. Even at city driving, the temperature stays optimal. The only thing I had to do a couple of times is to add coolant when it goes below the minimum after the engine has cooled down of course.

 

I guess what you said about expanding hoses makes sense and explains why the coolant drops so significantly.

 

Now that you mentioned finding the cause, could it be that it happened due to bad engine mounts? (all 4 of them). I had them replaced almost a month ago after driving with bad ones for like half a year. Can unhandled engine vibrations cause a blown head gasket or something like that?

We will see how it goes, I will definitely post the result after everything is done.

 

 

 

 

 

 

@_superB__

 

So the problem started shortly after replacing engine mounts? Maybe something got damaged during this? 

@jafo

 

Now that I think about it, it did happen once before engine mounts were even replaced but because a long time passed before it started happening more frequently, I guess I just added a bit of coolant and forgot about it. 

Do you think that unhandled engine vibration (bad mounts) could have caused the head gasket to be blown at first place?

No.