Astra J 1.7 Diesel EcoFlex major coolant loss

[Pumaracing]

crossy67 said:

I'm sorry but I can't see how an engine can suck coolant into its self.

You may not be able to see how but they do. On the intake stroke coolant can be drawn into the cylinder and on the compression, exhaust or power strokes gas can be forced into the cooling system. Head gaskets are tricky buggers. Sometimes when they fail they seal in one direction but not the other and vice versa.

[andyiley]

Pumaracing said:

But the coolant doesn't get hot until it's lost so much that it boils. A water pump can't do that.

No, the water gets hot because it is spending too much time in the hot part of the engine and absorbing too much heat.

[crossy67]

Pumaracing said:

You may not be able to see how but they do. On the intake stroke coolant can be drawn into the cylinder and on the compression, exhaust or power strokes gas can be forced into the cooling system. Head gaskets are tricky buggers. Sometimes when they fail they seal in one direction but not the other and vice versa.

If it's got a leak bad enough to allow water, a viscous liquid to be drawn in under the tiny vacuum of an induction stroke it would expel water like old faithful under the 100? bar power stroke no? Combustion gasses forcing their way through a tiny fault and pushing out coolant through a pressure relief system (cap).

Far more likely to be a cracked head.

[Pumaracing]

How does the issue of water getting drawn into a cylinder or gases getting forced out of it differ between a cracked cylinder head and a similar leak in a blown gasket?

[Pumaracing]

andyiley said:

No, the water gets hot because it is spending too much time in the hot part of the engine and absorbing too much heat.

Of course the coolant gets hot if the water pump fails but the OP tells us this is not happening. So it can't be the water pump.

[andyiley]

OK, so am obviously imagining the bits where the OP says the temperature is up from normal, and the water boils out when he opened the cap off the expansion tank.

I am probably also imagining the bit where he says if he leaves the water to cool & opens the cap the level suddenly drops (which can only be caused by a vacuum being created due to the cooling of the coolant after it has expanded, expelled hot coolant, and then cooled)am I?

Classic symptoms of water pump FAILING TO OPERATE AT 100%, not failed, just not pumping as it should, seen it before.

[Pumaracing]

You appear to be missing the bit in his first post where he says "Temperature was rock solid as normal at 90°C on the gauge."

[crossy67]

Pumaracing said:

How does the issue of water getting drawn into a cylinder or gases getting forced out of it differ between a cracked cylinder head and a similar leak in a blown gasket?

I have given my opinion, it's backed up with reason and corroborated by other posters who say a cracked head is not uncommon these engines. I don't think I need to justify the logic any further really.

[andyiley]

Pumaracing said:

You appear to be missing the bit in his first post where he says "Temperature was rock solid as normal at 90°C on the gauge."

Followed a few lines down by the description of it being up a bit "maybe from 90 to 95"

Obviously I imagined that though!

[Pumaracing]

To the OP. I'm not going to bicker on here with individual posters but it's a shame when the signal to noise ratio drops so you get bad and confusing advice.

There are two basic types of cooling system fault.

1) The engine overheats first and then perhaps boils over and loses coolant.

2) The engine loses coolant and then eventually overheats.

The first is a thermostat, water pump or radiator fault. The second is a leak. That much ought to be obvious. From your description you have a leak. It could be an external leak or it could be a head gasket or cracked head. Rule out those which it isn't and you'll get to what it is.

[andyiley]

From the op's description he has no leak at all. He has an overheating engine that is expelling boiled water through the relief on the top of his expansion tank, or weren't you listening to that bit either?

[stevieturbo]

andyiley said:

From the op's description he has no leak at all. He has an overheating engine that is expelling boiled water through the relief on the top of his expansion tank, or weren't you listening to that bit either?

IMO that would still show very obvious signs of external leak via the expansion bottle.

The OP states there were no signs of loss externally, hence ruling out overheating on that basis.

[Pumaracing]

andyiley said:

From the op's description he has no leak at all. He has an overheating engine that is expelling boiled water through the relief on the top of his expansion tank, or weren't you listening to that bit either?

OK, I said I wouldn't bicker with individual posters but you are like a little dog with a bone it just won't drop even when it knows it isn't its bone.

The OP has made it abundantly clear the engine DOES NOT overheat. It's always rock steady at its normal 90C apart from ONE solitary motorway journey when it went up a bit to 95C. Still not enough to make it boil even if there was no antifreeze in the water AND no pressurisation above atmospheric from the filler cap. But it still loses water.

Gosh, how can that be? Because it's got a bloody leak.

The leak is into a combustion chamber. How do we know that? Because even with a new expansion tank and cap it still vents a bit from the expansion tank outlet and that can only happen when the system pressurises above the 20 psi blow off value from combustion gases. Most of that vent off will be gas but it will have some moisture in it and that condenses out as drops of water.

Most of the water loss is internal into the cylinder. Some will exit as moisture from the vent.

When the engine cools down the leak seals and a vacuum is created in the cooling system. That's why the water level doesn't drop until the OP takes the cap off and unseals the system. The coolant then finds its own level again.

It's about the most obvious description of the exact symptoms of a blown head gasket or cracked head there has ever been in the history of internal combustion engines. It's pointless worrying about which of those two things it is because the head has to come off in either case but it's 95% likely to just be the gasket and a small chance of it being a crack in the head. The symptoms of both are however identical.

If the problem was not to do with a leak the temperature would have to go off scale every time before any water was lost and then steam would start coming out of the blow-off vent on a regular basis.

There's nothing more to add to this topic until the OP reports back so that's me done. Bicker amongst yourselves.

Edited by Pumaracing on Sunday 9th August 12:12

[crossy67]

I bet there is a lot more water coming out the vent that he thinks. If it's leaking combustion gasses into the coolant via a tiny hole it (and from the OP's description it is) it would only be leaking under high load. Like when you're doing 80 on the DC or accelerating. Unless you have your head under the bonnet at this time you'd never know the true extent of the leak.

A piece of hose from the overflow to a catch can would expose the extent of the leak.

[andyiley]

Well said, you beat me to it, the water evaporates off before he has a chance to see it. It is after all boiling as it escapes the tank.

[stevieturbo]

andyiley said:

Well said, you beat me to it, the water evaporates off before he has a chance to see it. It is after all boiling as it escapes the tank.

If there is antifreeze in it, you'd need to be blind not to notice any traces of anything that is escaping.
It will leave residue that is very visible.

[bearman68]

Having read the previous many posts, could I suggest it might possibly be, maybe be a faulty EGR valve. They are water cooled, exposed to combustion gases, and would give identical symptoms to HG failure including on the sniff test. Before stripping the head, if it were mine, I would be tempted to bypass the EGR water cooling and see if it makes any difference. What's the worst thing that can happen? Water cooled EGR valves do not have the best reputation, at least with me.
Another possibility would be to chuck some steel seal into it - would prob sort a cracked head, porous gasket, or leaking EGR, (not really a main dealer ticket this though).

Interesting case though

[chriscross123]

Thank you everyone for your responses.

Good points about the fluid venting from the header tank - there is no anti freeze residue evident - good idea about setting up a catch pot to see what / how much is coming out of the vent, though awkward to do as the vent is effectively part of the tank moulding.

I have run the system up at idle (for longer than the previous time), and this time the radiator hose temperatures seemed ok - I managed to scrounge a thermal camera from work and the inlet was about 80°C with the outlet about 60°C cooler. No other obvious hot spots around the cooling system (at idle at least)

Having dug into the cooling system design, the EGR valve cooler is fed by an electric auxiliary water pump which draws water from the inlet to the radiator and returns it to the radiator outlet (I would have expected the flow direction to be the opposite way round, but apparently not). Hence the diagnosis from the garage that it is either a head gasket or EGR valve cooler. If I could rule at least one of them out I would be happy.

What I am not clear on is (assuming a failure of the EGR valve cooler) whether there will be exhaust gas present in the cooler if the EGR valve is closed (ie is the EGR valve on the exhaust side of the cooler or the engine inlet side). This means I'm not sure if disconnecting the EGR valve would be a valid way of checking where the problem is? As per bearman68's post I could bypass the EGR cooler temporarily, but figure I don't want to risk causing damage.

The other thing I'm not sure of is the one long (200+ mile) trip I did when the problem disappeared. I'm thinking there must have been something different about that trip, but can't think what.

I'm also a bit concerned that pressure tests have (reportedly) not shown up a leak, and bottle tests prior to the last one have also been negative? Is the volume of coolant I am losing just so minor that the tests can be expected to be inconclusive?

Cheers

Chris

[bearman68]

Continuing on the EGR theme for a moment - presumably you would only get combustion gases in the coolant if the EGR was open at that time. While I'm sure it depends on engine speed and load, the systems I have seen have the highest EGR opening on engine overrun at normal operating temperature - these tend not to be the conditions experienced during sniff leaks when it's mainly running on idle.
I really don't think there will be a big issue disconnecting the EGR water supply. (Could even use a hose clamp and clamp it off maybe). If you worried that it will overheat, I suppose it would be possible to disconnect the electrical connection to the EGR solenoid. That will stop the hot exhaust gasses passing through the cooler, and prevent any overheating. (prepare for EML light on, and possible limp mode)
I read the comments about the heaters working OK, and I tend to agree that this is indicative that the water pump is more likely good than bad.
Bookmarked for interest

[andyiley]

stevieturbo said:

andyiley said:

Well said, you beat me to it, the water evaporates off before he has a chance to see it. It is after all boiling as it escapes the tank.

If there is antifreeze in it, you'd need to be blind not to notice any traces of anything that is escaping.
It will leave residue that is very visible.

As can be seen in the video, there isn't any.