B230FK Cooling System Pressure... or not!

[Simmo940]

Advice needed re b230fk cooling system pressure: since I've owned my 940 i have heard gurgling noises from heater matrix hoses when driving and pressure popped the rad bung twice. This has now been tied in 🙈 but I'm still hearing the watery noises and top rad hose feels hard, not rock hard but considerably harder than cold.

Have I got a problem or should I just turn boost up and send it?!

I thought it was heater control valve dragging air in as that was weeping, replaced but no difference. Ive replaced thermostat and flushed, opened out expansion tank return hole. Water pump is nearly new. I have done compression test and all circa 150psi, and sniff test for exh gases is also clear. Could it still be head gasket? It is using water and I get white smoke for first few minutes on startup.

I'm wondering if it could be the turbo?

[Chooch84]

If the turbo water cooling pipes are higher or level to the coolant tank then you’ll get funny noises...

Other than that, someone on here will probably be able to point you in the right direction.

[Laird Scooby]

I'd try a new expansion tank cap for starters, only about £6 give or take on fleabay or even your local parats factors.

Might pay to double check which you should have, there are two, one is 16.5psi (1.1bar, 110kPa) and the other is 22.5psi (1.5bar, 150kPa) not that either pressure should pop the rad bung if they are working correctly.

Don't forget, if you've tied the rad bung in, then whatever pressure is being created needs somewhere to escape, if it defeats whatever you've tied it in with, that rad bung could be lethal! Failing that, if it pushes a core plug out, Sods Law states it will be the hardest ro replace and/or the most costly. Some cars have one in the back of the blcok which necessitates the gearbox to be removed and the flywheel/driveplate & torque converter depending whether manual or auto.

It could simply be you've got an airlock in the system and it won't self-bleed because the expansion tank cap has failed and won't let the excess pressure escape.
As i said, try a new cap, top up with coolant and monitor the level for a few days, listening for the gurgling sound as you go.

[Simmo940]

Thanks for your replies.

I forgot to mention I have brought a new cap as well and it was no different, can't remember the pressure off the top of my head but it matches the cap that was on it.

I was going to remove water feed and return from turbo to take that out of the equation but noticed it has a third fitting so not easy at all!

[Laird Scooby]

A few questions in the light of knowing you've already replaced the expansion cap.

1. How long have you owned the car?

2. Did you renew the water pump and if so, what make is it?

3. Have you done a cooling system pressure test and/or a cylinder leakage test?

4. How soon after starting from cold does this excess pressure appear?

5. When you say there are three pipes on the turbo, are two of them coolant and the third the oil return? Don't forget there will also be an oil feed pipe.

6. Is it white smoke or steam from the exhaust on a cold start? If it's steam, are there clouds of it accompanied by a misfire or is it just a small amount that quickly disperses in the air?

[Simmo940]

Many thanks for your input so far. See below.

Originally Posted by Laird Scooby

A few questions in the light of knowing you've already replaced the expansion cap.

1. How long have you owned the car?

3mths

2. Did you renew the water pump and if so, what make is it?

It was done by previous owner just before I got it, knowing the other work it was most likely the most cheapest, nastiest one he could find!

3. Have you done a cooling system pressure test and/or a cylinder leakage test?

I have only done a 'dry' compression test, and a combustion gases leak test using fluid above expansion tank

4. How soon after starting from cold does this excess pressure appear?

Idling and warming up the pressure doesn't seem to increase, but drive it and it does. Although I'd like to retest this theory.

5. When you say there are three pipes on the turbo, are two of them coolant and the third the oil return? Don't forget there will also be an oil feed pipe.

Two are the coolant feed and return for sure, each side of the central turbo core, the third is in the centre of it. I don't recall noticing the oil lines as I was expecting them to be braided... like Cossie's of that era that I'm used to!

6. Is it white smoke or steam from the exhaust on a cold start? If it's steam, are there clouds of it accompanied by a misfire or is it just a small amount that quickly disperses in the air?

On cold startup only and quickly disperses yes. Possibly condensation steam but hard to tell as it's very rich when cold.

I did forget to mention that it is VERY rough when starting for first 30s, like it's running on 3, but clears itself within the minute and you don't need to raise revs to keep running.... this could be a separate issue though.

[Laird Scooby]

"6. Is it white smoke or steam from the exhaust on a cold start? If it's steam, are there clouds of it accompanied by a misfire or is it just a small amount that quickly disperses in the air?

On cold startup only and quickly disperses yes. Possibly condensation steam but hard to tell as it's very rich when cold.

I did forget to mention that it is VERY rough when starting for first 30s, like it's running on 3, but clears itself within the minute and you don't need to raise revs to keep running.... this could be a separate issue though."



I think it's all related. Sometime soon, when you know you don't need the car first thing, take it for a drive in the evening. Not far, just enough to get it warm. When you return, let the engine cool a while (30-60 minutes) so you can safely open the expansion tank cap and top up the coolant. Leave the cap off and run the engine for a few minutes until the bubbles stop in the tank or it starts throwing coolant out of the tank and then replace the cap.

Next morning, don't start the car, remove the plugs one by one and i'm fairly sure you'll find one that is wet with coolant.

Do you happen to know if the previous owner changed the head gasket at all? I have a couple of ideas around this, one of which was something that caused me a similar problem with my last 740 and all in all, sounds very similar to your symptoms.

As for the cheapest, nastiest water pump, probably a safer bet than a genuine Volvo one these days!

[Simmo940]

Ok will try that.

I did also forget to mention that I've not once witnessed bubbling within the expansion tank.

Headgasket has not been changed to my knowledge

[Laird Scooby]

Maybe no bubbling in the expansion tank because it's already lost coolant?

Handy to know about the head gasket, could influence the suggested course of action depending on the plug wetness test.

[Simmo940]

Ok will do when I get chance at end of week.

I have ordered headgasket set anyway in preparation!