My Cooling system - Still not right - what now?

[Ps3000]

Thanks all. For now, I have ordered one of those kits that has a chemical that changes colour in the presence of combustion gases. I'll use that when it arrives (likely on Thursday).

If that suggests there are combustion gasses, I'll decide whether to make a leakdown tester - I already have a compression tester I can dismantle and various air fittings (and a compressor) so I can probably mackle one up already - the only thing stopping me from doing that at present is the amount of dismantling required to get to the rear bank plugholes and the faff of finding TDC for each of the six pots.

If the chemical tester says there are no combustion gases, I will probably bypass the oil cooler - I have long suspected this personally, but I don't have a good logical or analytical reason, so I've tried to be rational about it instead.

As for bleeding the system - thank Simon, for the advice and link to the procedure which I printed and followed when I did the radiator, and again when I recently did the inlet manifold gaskets.

I'm not going to be so bold as to claim I cannot have done anything wrong and can't have missed anything, but so far as I can tell, I have followed the bleeding sequence properly.

One thing that has struck me each time, is that the part of the process where one waits for the level to rise, then screw on the cap, takes very little time - in other words the level rises almost immediately. The procedure doesn't say anything about how long this should take, but I suspect mine happens a bit qucikly.

[andy willi]

i think a cracked piston liner i have seen it once and it took me weeks to find it eventually found by stripping engine down did all the tests and no faults were found , only when the engine was pulled down did i find the fault , hope this helps .


andy

[RodgerD]

You can make a simple cylinder leak down tester using a cylinder pressure tester and an electric tyre inflator.

Even without the two gauge set up, much can be determined, air in the coolant, air in the inlet manifold, air leaking passed the rings and pressurising the sump. Leaking exhaust valves, with a 'stethoscope', long screwdriver, etc.

The problem is if you have a cracked liner, it might no show with a cylinder leak down tester as piston is at TDC and a leak down test cannot produce the pressures seen when engine is running.

You need a cheap compression tester, about a tenner, an good quality electric pump and a Schrader valve to whatever size thread is on the compression tester.

It would be worth you also doing a coolant pressure test, an electric tyre pump is ideal for this purpose. I use a spare header tank with a tyre valve inserted in the body of the tank, with a cap rigged not to blow above 140Kp.

I made my adapter out of a V6 fuel test point pipe (fitted at the end of the fuel rail), brazed into a suitable threaded fitting that screws into the compression tester.

Yes its basic and the tyre pump only produces a low volume of air, but it does pump to a reasonably high pressure and at TDC there is minimal volume to pressurise. The rate pressure falls will determine if you have a problem with a cylinder, ideally they all should lose pressure at the same slow rate which can be interpreted as a sound cylinder.

[Ps3000]

Originally Posted by andy willi

i think a cracked piston liner i have seen it once and it took me weeks to find it eventually found by stripping engine down did all the tests and no faults were found , only when the engine was pulled down did i find the fault , hope this helps .


andy

Andy - I assume the engine had to come out for this?

[Ps3000]

So my block tester arrived yesterday and today I got a chance to use it, but before that, I made a couple of videos that I'd welcome the views of the panel on.

First of all, just to show my initial coolant level. Oddly, it hasn't lost any in the last couple of days, but anyhow -

https://youtu.be/pPnYQQS-gDY

In order to use the block tester, one needs to start the engine and insert the kit in the filler neck, but my problem was that the coolant level rises way too fast -

https://youtu.be/caZp4j3V-cM

Is it just me, or do those flecks in the top look like K Seal?

Anyhoo, I got this sort of thing for a while -

https://youtu.be/h-8mspxDUe4

But after it had spat a good load of coolant out, it calmed down enough for me to use the gas tester. After several minutes, the liquid resolutely refused to turn any other colour than the original blue, which in theory means there are no combustion gases in the cooling system.

[SD1too]

Originally Posted by Ps3000

First of all, just to show my initial coolant level.
https://youtu.be/pPnYQQS-gDY

I found it difficult to see the level in your first video John due to the camera's exposure. Try zooming in to the neck of the tank so that the coolant area almost fills the frame. But you know where the level should be: no higher than the 'max' marker.

... my problem was that the coolant level rises way too fast -
https://youtu.be/caZp4j3V-cM

The initial level is much too high. I see that the surface is smooth, with no bubbling. I've never had a failed gasket, but in that event wouldn't you expect to see combustion gases escaping as bubbles? The steady rise in level looks to me like air or, as you suggest, a blockage caused by a sealant additive (if it's possible that that has happened).

Simon

[SD1too]

I've just reviewed the thread history, so here are some more observations.

Originally Posted by Ps3000

Temp monitored today during a 15 mile trip on OBD ranged between 87-96 once warmed up. It drops into the 80s when setting off from rest, climbs and sits at 90-93 on cruising at 50-60, ranges from 90-96 sitting in traffic.

John; your temperature is very unstable. Mine sits in the low nineties all the time except when I'm stationary in traffic. Dropping to the eighties isn't correct. Behaviour like this usually means that there's a pressure loss somewhere in the cooling system.

Originally Posted by Ps3000

... after I did the inlet manifolds.

Did you bleed the syetem when refilling after this repair work? Note that in MGR's instructions the expansion tank cap should be refitted when the level begins to rise.

Simon

[Ps3000]

Originally Posted by SD1too

I found it difficult to see the level in your first video John due to the camera's exposure. Try zooming in to the neck of the tank so that the coolant area almost fills the frame. But you know where the level should be: no higher than the 'max' marker.

Sorry about the poor quality, when I zoomed in the autofocus didn't work as it was too dark - the level was just below the full marker.

Originally Posted by SD1too

The initial level is much too high. I see that the surface is smooth, with no bubbling. I've never had a failed gasket, but in that event wouldn't you expect to see combustion gases escaping as bubbles? The steady rise in level looks to me like air or, as you suggest, a blockage caused by a sealant additive (if it's possible that that has happened).
Simon

That "initial level" is what happens as soon as I start the engine - with the correct level at the outset - it rises really fast.

[Ps3000]

Originally Posted by SD1too

Did you bleed the syetem when refilling after this repair work? Note that in MGR's instructions the expansion tank cap should be refitted when the level begins to rise.

Simon

Yes I bled it using that 6 point process (I printed it out and followed it to the letter). One of the questions I had earlier in the thread was about that step - in order to follow that part "put the cap on when the level starts to rise", I have to start the engine, and run around to put the cap on, cos it starts to rise immediately. It's buried in the thread, but a question I had was "is this normal"? because it seemed odd to me.

As I said before, I'm not daft enough to feel I can't have made an error in the bleeding process, or something else.

As for my temp instability - it's been like that ever since I've been able to monitor it using the OBD. It always drops to the high 80s when setting off from traffic lights etc.

[SD1too]

Originally Posted by Ps3000

I have to start the engine, and run around to put the cap on, cos it starts to rise immediately ... "is this normal"

No.

As for my temp instability ... It always drops to the high 80s when setting off from traffic lights etc.

That's not normal either. John, I think you may be right about the K-seal. We've had these situations before, where nothing makes sense. So what can you do? To try to identify the cause, it would be interesting to know the temperature of the bottom hose (that which contains the bleed screw). As the engine warms up the top hose should increase in temperature but the bottom should stay cool until the thermostat opens. Does it do that, or does it roughly follow the top hose's temperature?

Another approach would be to drain the cooling system completely, not forgetting the cylinder block drain plug, and use a low pressure garden hose to flush as much as you can. The oil cooler is a favourite place for K-seal to form a dam, so if you detach its outlet hose as well you can test it for obstructions (someone earlier in your thread suggested by-passing the cooler).

You certainly have a cooling system problem John, but your videos and chemical test suggest that it's nothing to do with combustion gases.

Simon