Not sure if anything on this topic on the forum so far, but here it goes.

Problems identified:

1) Water pump kept making a noice and this was being "monitored". Otherwise engine runs smoothly.

2) During winter time here in Finland (bellow 0 C pretty much all the time) no problems with the cooling system. Car kept outdoors and rather long periods of no driving in between, up to 3 weeks. Sometimes rather cold temperatures -25 C.

3) First warmer days and heavier drive, water bypass tube bursted. No warm air in the car any more, engine temp up => car stopped and towed home.

4) Water pump, belts and bypass hose fixed. Engine runs smoothly and waterpump noice is gone. Car stress tested at the carage, engine runs smoothly, temperatures are ok, no leaks... Not able to drive the car as no insurance at that time.

5) After 20 km of drive in warm weather and speed max 110 km/h car is parked and I noticed steam coming under the bonnet. Opened up, and radiator inlet hose looked like a ball and coolant water was visible on the engine.

6) Inlet hose blew up with a nice steam effect.

Now the question is, "Is this for sure a cylinder head cover casket issue, or could it be something else?" Different theories have been provided: bad luck with two old hoses, thermostat is not working, cooling system is blocked somewhere and the coolant is not circulating properly... All the time the engine runs smoothly.

Next steps planned:
1) Replace the radiator inlet hose
2) replace thermostat
3) Take HC measurements from the exhaust pipe and radiator assy to see if the gases are mixed in a wrong place => if yes, cylinder head casket leaks
4) If HC measurements are ok and problem persists, empty the cooling system and blow air to see if anything blocking.

Any additional ideas what to do, sure things or any good links to show how to troubleshoot?

Thanks in advance,
jukka

I think your own answers cover everything already

The only thing I would add is check the radiator fan/switch is working

The symptoms soung like bad luck with old hoses to me if it doesn't overheat on boost but HC testsmwill prove everything

The radiator cap should release pressure into the overflow bottle before there is enough pressure to blow up a hose like a balloon - regardless of whether head gasket is pressurising the system.

Check the radiator cap spring isn't jammed - or replace anyway - and check the pipe to the overflow bottle isn't blocked by blowing through it.

I suspect old rubber hoses don't like getting so cold and standing still.

What model is it ? 165/185/205

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If at first you don't suck seed, try drier grain.

thank you for the tips,

It is ST185, All track version originally from US. Roughly 10 years in Finland.

And the fan kicks in when needed.

Hi,

please check also the radiator, it must be nearly clean inside

long time ago a friend of mine have the same "ball" upper radiator hose, but it was in front of a totally brown dirty radiator -> not enough flow any more

greetz

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KEEP COOL UNDER PRESSURE

street legal?.....perhaps in tschibuti

The culprint seems to be the radiator cap. Now it is changed and no more problems. The HC measurements were taken from the expansion tank, and it showed 0 for HC (went to 008 for ½ second, then back to 0).

Do you know if the radiator cleaning liquids are any good for? I'm thinking about using that stuff and replacing the thermostat as well.