This morning was the second time the same ancillary coolant hose burst in my car. It's a 2005 model Opel/Vauxhall Astra turbo coupe (engine is Z20LET). Prior to this, I have had many problems with coolant leaking out of the joint where the pipe connects to the reservoir.

I know exactly how to replace the pipe (unscrew clamps and take off the old one, then attach the new pipe and fasten the clamps), but I was wondering what the cause was and if anyone has had similar problems. I would like to avoid this problem in the future.

My car doesn't run terribly hot, even in slow traffic in summer. The temperature hardly ever goes over 95 to 100 degrees celsius (203 to 212 Fahrenheit). I've also taken care to eliminate air bubbles in the coolant system by idling the car with the radiator cap off when I top up the coolant.

But even then, I suspect that the pressure may be too high in the coolant plumbing. Or else the pipes may have perished, being 8 or 9 years old. I don't think I have a blown gasket, but if you knew my history with the car, I wouldn't even be surprised. Although engine performance is very good and I don't have a rough idle or lumpy acceleration.

Extra info: I had my aircon on a lot the previous day and I have this feeling that I may have had it on a lot the previous time this happened.

UPDATE: some pics of the usual suspects showing no signs of a blown head gasket. enter image description here Oil cap Coolant Burst pipe

  • 1
    If it were perished hoses I'd expect a different one to burst the second time, not the same one again, as presumably you fitted a new one when it burst the first time... Have you replaced the pressure cap recently?
    – Nick C
    Jan 27, 2014 at 10:17
  • It may just be the angle of the photo but is the hose kinked where it goes under the upper (large) radiator hose.
    – mikes
    Jan 27, 2014 at 11:25
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    I'd have the engine checked for a blown head gasket. If combustion is forcing pressure into the cooling system, it could be causing your over pressure. It just might be, the pipe which has blown is just the weakest point in the system. Rerouting this pipe and thus causing the kink in the pipe might not be doing yourself any good either. The kink could be part of the problem, as the two rubber pipes allow fluid transfer into/out of the overflow tank. The kink definitely puts a greater strain on the pipe. Jan 29, 2014 at 12:38
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    Just because you don't have the classic "chocolate milk" in your engine oil, does not mean you don't have a blown head gasket. Especially considering you have a turbocharged engine. The force from combustion is far greater in a forced induction engine than it is in a naturally aspirated one, which means it can force its way past without letting any coolant go the other way. Have the coolant checked for combustion gasses, if for no other reason than to determine this is not your problem. Feb 1, 2014 at 14:56
  • 1
    Another thought ... You said in the comment above, you "Haven't replaced anything yet." Does this mean you cut off the bad part of this hose and reattached it, thus having to reroute the same OLD hose over the top of the battery so it would fit? If so, your problem is the old hose is old and needs to be replaced with a new one, which should thus be routed back the way it was from the factory. Feb 1, 2014 at 15:03

3 Answers 3


For the sake of any others with the same problem, I'll add an answer:

After eliminating the signs of a blown headgasket, i.e.

  1. Engine sputtering under load
  2. White smoke from the exhaust
  3. bubbling coolant
  4. milky coolant in the reservoir
  5. chocolate milk-like deposit on the dip stick and/or rocker cap(yellow cap pictured)

The only other thing to do is to have a Carbon Monoxide test performed on your engine's coolant. This has to be done at a workshop because it entails the use of special equipment for detecting this invisible gas.

If Carbon Monoxide is found in the coolant, it would mean that the gasket blew in such a way that a tiny amount of exhaust gas is leaking into the cooling system, thus heightening the pressure in the pipes and causing the weakest link to burst.

But if no Carbon Monoxide is found and all other symptoms have been eliminated, the only other thing that could possibly cause this amount of over-pressure would be an air pocket somewhere in the system. This can be remedied by removing the radiator cap or expansion bottle cap and letting the car idle until the fan comes on, at which point you can turn the aircon to HOT and let it blow on full until some bubbles start to come up out of the coolant and the level goes down, filling the space left by the bubbles.

If that is still not the answer, it could just be that the pipe had perished and was in need of replacement. In which case it is well worth the extra 30 minutes to 2 hours it would take to replace the others. Unless you like standing on the side of the road.


If Carbon Monoxide is found in the coolant, it would mean that the gasket blew in such a way that a tiny amount of exhaust gas is leaking into the cooling system, thus heightening the pressure in the pipes and causing the weakest link to burst. this statement is 100% correct I had the same problem with my z20let I took out the cylinder send it for cylinder head service refit the head my problem was solved


Just had this checked. Coolant surge tank replaced. Hose to turbo replaced. Went out and overheating again, with the cap being the problem. So check the cap.

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