High Pressure in Coolant Tank

[hibbsy21]

As most of you will know I have just upgraded the turbo on my 1.9tdi. All is well and just doing a few MOT repairs. But I am not happy about the coolant. The main pipe that goes from the head to the radiator is really hot and hard after a run. And when I undo the tank cap it releases a hiss of pressure and the little pipe that goes into the tank shoots water through it into the tank. Just a bit confused as to why and i am not happy with it.

The only things i can think of are; the tank cap is blocked (already cleaned and blasted with an air gun), a blockage elsewhere in the system (going to drain and flush out thoroughly), the turbo is creating a high pressure inside the head....? (actuator not set up properly yet and running a massive boost!)

Any other thoughts?

Rich

[mumutley]

What temp is being displayed?

[hibbsy21]

The temp is normal, 90C, but does take ages to get there. Left it running on idle today and the pressure still builds up. It's rather concerning.

Rich

[hibbsy21]

Well this hasn't become a problem, no hoses have burst so I guess its just a slight pressure block somewhere in the system. As soon as I get a few days free I will be doing a major flush out and the tank is going in the dish washer a few times.

Rich

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[mumutley]

Any joy?

Have you replaced the thermostat?

[zollaf]

my 80 did this, but the gauge was going a bit high, just above 90. loads of pressure. turns out the rad was blocked with sludge. i cut it open and could see through like 4 of the tubes, the other million were blocked.

[hibbsy21]

Meh, its fine tbh. The pipes are still quite firm after driving so I need to flush it all out soon. Oil needs changing next week. So I will do new coolant at the same time.

Rich

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[hibbsy21]

Right then. This is still a problem and becoming quite annoying. It started out with a leak, turns out the plastic flange that goes into the side of the head had a huge crack in it. Changed that, no more leaks.

Changed thermostat and water pump.

Used a 2 part coolant system flush.

So, you'd expect it to be fine and sorted. But its not. The hose that goes into the head is like a rock after driving and the coolant tank cap releases massive pressure when removed. I have blown into the pipe that goes into the head and it doesn't seem to move the water anywhere, is it possible that the channels in the head are blocked?

The issue is when I go over 60mph for more than 5mins the water starts to go up to 100-110C and boils over. So you can see I am running out of ideas. I might just get a new radiator just to make 100% certain that it isn't blocked, before I rip the head off.

Rich

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[mikeybutch]

It could be the Rad.Can you feel over the bottom area ?if so and its cold or cooler than the rest thats a sign of sludge build up and its very hard to shift

[hibbsy21]

Yeah, only a small amount of the rad ever gets hot on idle. Then its only warm on the far side. The water that comes out of the bottom pipe is really cold.

Thanks for that, needed a second opinion before I got a new rad. Will get that sorted this Sunday/Monday and report back.

Rich

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[turpal]

Looks like w/pump impeller gone from what you saying.Get it inspected before you bow head gasket.

[Dan J]

I had this similar problem over a period of 8 to10 months,high pressure in the tank which eventually turned into the level sitting at minimum,
while I was having the cambelt changed we checked the water pump and all was good, new thermostat was put in, rad flushed out properly and all was good there,

Still had the same problem, it turned out to be the oil cooler in the end, it spat oil (lots of) into the coolant, after much flushing and a new oil cooler all is well and the level sits where it should and no more build up of excessive pressure.

Not saying this is your cause but it's worth investigating!

[hibbsy21]

Looks like w/pump impeller gone from what you saying.Get it inspected before you bow head gasket.

I changed the water pump a week ago.

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[hibbsy21]

I had this similar problem over a period of 8 to10 months,high pressure in the tank which eventually turned into the level sitting at minimum,
while I was having the cambelt changed we checked the water pump and all was good, new thermostat was put in, rad flushed out properly and all was good there,

Still had the same problem, it turned out to be the oil cooler in the end, it spat oil (lots of) into the coolant, after much flushing and a new oil cooler all is well and the level sits where it should and no more build up of excessive pressure.

Not saying this is your cause but it's worth investigating!

Yeah, the oil cooler popped in to my mind the other day.

Going to change the rad tomorrow and see how it is. If its still over heating and building pressure then the head is coming off and the oil cooler replaced and the whole system cleaned out part by part. And I'll be replacing the piston rings and shell bearings while I'm at it.

Rich

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[turpal]

If the oil cooler went pop you know it went pop and it will pressurise.

[hibbsy21]

Got a new rad from ECP today £36! Seems to be good quality too. Fitting tomorrow along with a list of other things I have been putting off. Such as the suspension arm that is knackered.

Rich

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[adamss24]

You have a blown head gasket, stop messing about it and buy new head bolts and a quality head gasket ! No point in replacing rings and bearings shells unless the engine has done 600k or more ! Trust me, been repairing this on a regular basis...

[turpal]

The cheapest and most sensible thing is to sniffer test to c if the head gasket gione and go from there.

[adamss24]

The cheapest and most sensible thing is to sniffer test to c if the head gasket gione and go from there.
Not working on diesel engines...

[turpal]

Not working on diesel engines...
I suppose,after doing so many on petrols I`m still in a petrol world lol

[zollaf]

i have tested many diesels with this kit, and only once had it change colour a tiny bit. mind you, i am not convinced it changed colour because of gas in the cooling system or a contaminated filter on the tester.

[adamss24]

The sniffer tests only work on petrol engines and even then you need to take them with a pinch of salt ! I had a 2.0 petrol passat with a cracked head a few weeks ago, owner had a backstreet garage do a timing belt job + water pump and did not bleed the system. Subsequently the owner put cold water in the hot engine as it was pressurizing the coolant tank and water went trough the relief valve. It never overheated and temp. stood bang on 90 C on the gauge. Took the head off, sent it for skimming and pressure test and then refitted with a new head gasket and head bolts. It did the same after 3-4 days, water dropping from the header tank, told the chap his block is cracked so he needs a 2nd hand engine, he did not take it nicely !

[ShaneA4]

As most of you will know I have just upgraded the turbo on my 1.9tdi. All is well and just doing a few MOT repairs. But I am not happy about the coolant. The main pipe that goes from the head to the radiator is really hot and hard after a run. And when I undo the tank cap it releases a hiss of pressure and the little pipe that goes into the tank shoots water through it into the tank. Just a bit confused as to why and i am not happy with it.

The only things i can think of are; the tank cap is blocked (already cleaned and blasted with an air gun), a blockage elsewhere in the system (going to drain and flush out thoroughly), the turbo is creating a high pressure inside the head....? (actuator not set up properly yet and running a massive boost!)

Any other thoughts?

Rich

Did you ever get this sorted having the same problem cheers

[Victordugg]

Did you ever get this sorted having the same problem cheers

I also have the same problem has anyone resolved the issue?

[FrenchAudi]

I also have the same problem has anyone resolved the issue?

It is normal for the pipe to get quite hot and for the tank to be under pressure once the engine is at working temperature. The cap should not be removed when it is hot.

Is your temperature gauge reading higher than normal, i.e. more than 90º?

Are you removing the cap before the engine has cooled down?

[Victordugg]

My question was with regards to the original post 'high pressure in coolant tank' i'm having the same problems, pressure got so high it popped the radiator (which was the first thing the mechanic changed about a year ago). Ive also changed the water pump and thermostat still no joy. Thinking of buying a second hand engine but i think i'm going to have one last go with changing the oil cooler. But I the oil isn't mixing with the coolant, can it still be the oil cooler? Also does anyone know how I can tell if it's got an egr cooler, where would it be located? I've read in another thread, someone with similar problems changed this and problem as fixed.

[alowsa91]

Hi guys, after chasing a similar problem on my b5 with a 115bhp ajm engine code it turned out to be the headgasket. I was having similar issue; rock hard top hose, pressurised bottle etc. I sniff tested it and it passed sniff test, changed expansion bottle and cap with genuine parts and a genuine stat. Nothing resolved it till I pulled the head. Hope this helps.