Too much coolant pressure

[ZsZ]

It seems like I have some coolant problems.
On longer high RPM trips (like 1-1.5 hr highway above 4000rpm) pressure builds up in the coolant system.
I have lost a few hoses in the past years and now the rear heater matrix.

A bad coolant cap (relatively new Blau one) can cause this, or it is sign of a starting head gasket problem?
I had no such problems before the cap as I remember.

The engine is an 1Z mtdi with all JX stuff other than the diesel pump.

Any suggestion?

[metallikart]

Good morning,
first thing you could try is, as you also suggested, to exchange the blue cap.
(You should not buy the cheapest one you can get)

Did you vent yous system properly? Thats always very important?
The container with the blue cap is necessary to be filled up to the top.

Kind regards, Christian

[Atlantik90]

It seems like I have some coolant problems.
On longer high RPM trips (like 1-1.5 hr highway above 4000rpm) pressure builds up in the coolant system.
...

I think you will drive above the limits of your cooling system with long time above 4000 rpm.
If the blue cap will be the reason for your defects you can check according the procedure in the workshop manuals using a tester. The preassure valve should open at least at 1,3 bar. Up to this preassure it is normal at normal opperation due to increase of volume during warmup.

[ZsZ]

Thanks for the infos.
The cap was the most expensive Blau branded one - made in Germany. I disassembled it and it seems the tabs that holding the spring-valve assembly together deformed and let the spring plate open.
Not sure if this was due to overheating.
Will post pics later.
I had no such problems with my old cheapo two valve cap. Unfortunately I did not take with me as a spare.
The system was full and without air - a few years ago I washed all the system and gave the front radiator an acid bath when I installed the new motor for the cooler fan.
Coolant was 1:1 G12+ mix.
I will do a proper cooling system check by the book when I get home from vacation. Until that I will keep the RPMs down.

[ZsZ]

I have problems posting the pics.
Here are they:
https://imgur.io/ATtpgo5
https://imgur.io/hLqPZmc

[ZsZ]

After the SOS repair (VanWesel branded chinese radiator, Japanparts branded EU+ coolant cap with the crappy two valve design) we made ~700kms to croatia (no highways)
The bottle behind the licence plate still has the clear distilled water I put in after the bleed.
I am not sure if this is good or not.

[metallikart]

Good morning,
you should always take care of the correct mixing ratio between water and antifreeze.
Its important to protect the whole system (e.g. corrosion) and the water pump needs the anti freeze as a lubricant.

kind regards, Christian

[ZsZ]

Thanks Christian,
I have G12+ coolant from local manufacturers (eg. MOL) in around 1:1 or 1:1.5 ratio (~25C mix)