Anyone come across a top-hatted block failing?

[Pupp]

As in coolant either ending up in the chamber or the sump?

[QBee]

Pupp said:

As in coolant either ending up in the chamber or the sump?

Ask Phased - I think he had an issue like this last year. I seem to remember much angst and trips to Chesmans

[Engineer1949]

yes not specifically in tvrs but plenty in rangys etc. it seems to stop the liners moving but thats about it.


john

[Pupp]

Interesting John... I'm getting coolant over- pressurisation but no sign of HGF... gasket clamps onto liner flanges, which are all level and true to deck etc yet combustion gases still getting to water jacket. Blowed if I can suss the leak path

[phazed]

Gary. When I had a crack in the block behind a liner, lost coolant through the crack and then from the gap in between the base of the liner and the block.
Obviously something that you cannot see until the liner is removed.

My very obvious symptom was huge amounts of mayo in the rocker covers.

You haven't got this so the likelihood of water escaping into the block/sump is unlikely/impossible otherwise you would have a major mayo problem as well!

A leaking head gasket from a waterway into one of the bores seems to be a very likely cause. Anywhere else and you would see it externally.

[Pupp]

Thanks Peter.... I'd expect to see some evidence like a cleaner combustion chamber or an obvious failure tell tale on the gasket face... there's zip. No obvious hydrocarbons in coolant either...

[Classic Chim]

Excuse my ignorance if this is a numpty question but would a sticky thermostat that causes the engine to get very hot before eventually the stat opens possibly cause over pressurisation and then blow water out.

[phazed]

Or even a failed expansion tank, they are known to leak occasionally. I would've thought that you may have seen evidence of water staining on the aluminium tank if this happened.

[Boosted LS1]

Pupp said:

Interesting John... I'm getting coolant over- pressurisation but no sign of HGF... gasket clamps onto liner flanges, which are all level and true to deck etc yet combustion gases still getting to water jacket. Blowed if I can suss the leak path

Maybe a crack next to a valve?

Oops misread the post. I'd second the expansion tank cap. I've had this problem before.

[phazed 11.83]

I did mean expansion tank Which if I remember correctly was a citroen item .

[N7GTX]

phazed 11.83 said:

I did mean expansion tank Which if I remember correctly was a citroen VW/Audi item. part number 443121321

[Steve_D]

I'm confused.
OP you are saying in one post 'gasket clamps onto liner flanges, which are all level and true to deck etc yet combustion gases still getting to water jacket' then later say ' No obvious hydrocarbons in coolant '.

Those two cannot work together.

Without the hydrocarbons I would suspect you are not maintaining pressure which brings on boiling then too much pressure.
Am I right in thinking you did some changes to coolant pipes and flow paths a while back? Could these be causing hot spots and localised boiling somewhere?

Steve

[Engineer1949]

just a little more info some of the failures where down to a hairline crack just below the top hat flange i think probably down to poor machining and something not being just snug.


john

[Pupp]

Steve_D said:

I'm confused.
OP you are saying in one post 'gasket clamps onto liner flanges, which are all level and true to deck etc yet combustion gases still getting to water jacket' then later say ' No obvious hydrocarbons in coolant '.

Those two cannot work together.

Without the hydrocarbons I would suspect you are not maintaining pressure which brings on boiling then too much pressure.
Am I right in thinking you did some changes to coolant pipes and flow paths a while back? Could these be causing hot spots and localised boiling somewhere?

Steve

Not arguing with the logic and confess to being confused; 2 sniff tests have not ID'd combustion gases in coolant but it is ejecting coolant (at some rate). Yes, the plumbing has been revised (there's a thread as to how and why but it's a common enough mod and others have reported no problems so think that was just a coincidence (other changes were made including to boost pressure so I'm thinking that's a red herring).

I really don't understand the localised boiling theory (it gets mentioned a lot) - pressure will equalise throughout the system and allow boiling wherever at a specific temperature that depends on that pressure. If it boils, then yes steam volume will increase pressure (rapidly) and maybe something is allowing that (a pressure leak would do but there is no obvious sign of that and cod pressure tests are in a decent enough range).... the OEM system allows for an engineered in airlock by the way - look at the top hose angle on a serp.

Best thing I ca come up with is a very marginal and perhaps directional gasket leak across the head joint, or maybe across the inlet manifold and sensitive to positive boost (maybe when hot)... or a cracked liner like described by John (will inspect when the pistons are out).

I realy want to 'find' something as this has been a pisser of a problem that has written off the whole of this season. I don't want to rebuild and have a recurrence but, equally, I don't want to needlessly replace what otherwise looks like a serviceable bottom end.

[QBee]

I am new to turbo ownership. I have an Emerald ECU controlling mine, so a choice of maps and boost settings, and the higher the boost, added to the kind of driving that requires the extra boost (track day, so on boost for 80% of the time), caused seriously high temperatures in my engine bay as indicated by the water temperature gauge. Could the increased boost you mention perhaps not be so much of a kipper rouge (as the French don't call it)?

[Steve_D]

Pupp said:

......I really don't understand the localised boiling theory (it gets mentioned a lot) - pressure will equalise throughout the system and allow boiling wherever at a specific temperature that depends on that pressure. If it boils, then yes steam volume will increase pressure (rapidly)............

Yes, if the system is up to pressure then the boiling point will be the same anywhere in the system.

What I am thinking is that your new coolant system layout is causing poor coolant flow in one or more areas of the heads. If there is reduced flow then a hot spot could form and it goes down hill from there.

Steve