V6 pressurising coolant massively

FrazzleTC · 27th August 2015, 12:11

My father's ZT180 2.5 has been losing coolant for a few weeks now. It had a new thermostat housing six months ago as there are no leaks there. It has had four new expansion tank caps, every water hose has been checked, the lower coolant pipes are perfect, having been replaced a couple of years ago. However, whenever it gets warm, the coolant pressurises massively, and comes out around the cap. The car can be left sitting overnight and there is still a lot of pressure when the cap is removed. Some small amount of Mayo under the oil cap. Car does at least 500 miles a week.
I have owned five KV6 75s/ZTs and have not had this before. I'm usually very keen to defend these engines, but in this instance, I can't help thinking that It is a case of head gasket failure, given the symptoms!

Any advice gratefully received.

FrazzleTC · 27th August 2015, 12:14

I should add that the car is meticulously maintained. In October last year while on holiday, the original fan died, and the temperature went into the red. The car was turned off but I do wonder if this has led to the issue I describe...

T-Cut · 27th August 2015, 12:17

Quote:

Originally Posted by FrazzleTC

The car can be left sitting overnight and there is still a lot of pressure when the cap is removed.

I'm afraid there's only one explanation. Residual cold pressure is due to combustion gases pumped into the cooling system. If the cooling system is sound, it will remain in there at up to about 20psi (header cap relief pressure). There are one or two causes, all bad. A failed head gasket, a cracked head, a cracked liner.

TC

FrazzleTC · 27th August 2015, 12:26

Those were my conclusions too! I was keen to ask other interested owners to hear their views before I pull the engine out of my 2.5 75 to keep my father's ZT alive.

murphyv310 · 27th August 2015, 16:37

Get a sniff test done or buy a kit.
Does though sound like it could be one of the above that TC says.
Mind the 180 ZT is a Detuned 190 and your 75 will have the 160 unit upped to 177bhp. That'll slow down your Dad

Different torque curves and possibly a different response after a swap with differing tunes with a different MAP

Ooops Too many Different's !!!!

FrazzleTC · 27th August 2015, 16:38

The 75 it's coming from is a 177 2.5 auto, which has been doing sterling work driving me about over the last few weeks, so he shouldn't notice a massive difference, hopefully!

murphyv310 · 27th August 2015, 16:42

Quote:

Originally Posted by FrazzleTC

The 75 it's coming from is a 177 2.5 auto, which has been doing sterling work driving me about over the last few weeks, so he shouldn't notice a massive difference, hopefully!

Its only the camshaft profiles that are different to my knowledge anyway.

marinabrian · 27th August 2015, 17:10

Colin 2diesels has a good 2.5 KV6 engine Frazer, and I bet it won't cost the earth either

Brian

Jules · 14th October 2015, 00:40

Thread revival !

Frazzle you got to the bottom of this yet?
I've had 4 cases of this with 2.5 KV6's this year alone.
2 are here & the other 2 got scrapped by their owners due to cost.

Brian has Colin still got that engine if Frazzle doesn't want it?

Suspected cracked heads seem to be rearing their ugly heads although I've not seen one in the flesh yet.
Also is it even or odd bank head which fail the most I wonder?!

The front head is going to be subjected to wider temp ranges than the rear head for obvious reasons ie blasted with cooler air on the move and when stationary the fan cutting in and out will extend the temp range wider than the rear head.

On the other hand the rear head could run hotter because of it's position although in theory it shouldn't if water circulation is operating correctly.

There doesn't seem to be much evidence at present as to which head is more likely to crack.
It may not be due to cracks but aluminium may be going porous?

The more cases we can document of KV6 pressurising, the more we can understand the causes and cures

Jules

directstep · 14th October 2015, 08:30

Solely based on my own experiences - I'd plump for dropped/leaking Liners.....

27th August 2015, 12:11	#1
FrazzleTC This is my second home Rover 75 Tourer Join Date: Sep 2011 Location: Staffordshire Moorlands Posts: 7,924 Thanks: 533 Thanked 1,178 Times in 920 Posts	V6 pressurising coolant massively My father's ZT180 2.5 has been losing coolant for a few weeks now. It had a new thermostat housing six months ago as there are no leaks there. It has had four new expansion tank caps, every water hose has been checked, the lower coolant pipes are perfect, having been replaced a couple of years ago. However, whenever it gets warm, the coolant pressurises massively, and comes out around the cap. The car can be left sitting overnight and there is still a lot of pressure when the cap is removed. Some small amount of Mayo under the oil cap. Car does at least 500 miles a week. I have owned five KV6 75s/ZTs and have not had this before. I'm usually very keen to defend these engines, but in this instance, I can't help thinking that It is a case of head gasket failure, given the symptoms! Any advice gratefully received. __________________ 1967 Rover 2000 Automatic 1969 Rover 3500 Series One 1979 Scimitar GTE 2013 Mercedes SLK250 CDI

27th August 2015, 12:14	#2
FrazzleTC This is my second home Rover 75 Tourer Join Date: Sep 2011 Location: Staffordshire Moorlands Posts: 7,924 Thanks: 533 Thanked 1,178 Times in 920 Posts	I should add that the car is meticulously maintained. In October last year while on holiday, the original fan died, and the temperature went into the red. The car was turned off but I do wonder if this has led to the issue I describe... __________________ 1967 Rover 2000 Automatic 1969 Rover 3500 Series One 1979 Scimitar GTE 2013 Mercedes SLK250 CDI

27th August 2015, 12:26	#4
FrazzleTC This is my second home Rover 75 Tourer Join Date: Sep 2011 Location: Staffordshire Moorlands Posts: 7,924 Thanks: 533 Thanked 1,178 Times in 920 Posts	Those were my conclusions too! I was keen to ask other interested owners to hear their views before I pull the engine out of my 2.5 75 to keep my father's ZT alive. __________________ 1967 Rover 2000 Automatic 1969 Rover 3500 Series One 1979 Scimitar GTE 2013 Mercedes SLK250 CDI

27th August 2015, 16:37	#5
murphyv310 This is my second home Hyundai i10 998cc Join Date: Mar 2012 Location: Kilmarnock Posts: 6,602 Thanks: 2,088 Thanked 2,298 Times in 1,349 Posts	Get a sniff test done or buy a kit. Does though sound like it could be one of the above that TC says. Mind the 180 ZT is a Detuned 190 and your 75 will have the 160 unit upped to 177bhp. That'll slow down your Dad Different torque curves and possibly a different response after a swap with differing tunes with a different MAP Ooops Too many Different's !!!! __________________ Cheers from Trevor MM0KJJ Last edited by murphyv310; 27th August 2015 at 16:40..

27th August 2015, 16:38	#6
FrazzleTC This is my second home Rover 75 Tourer Join Date: Sep 2011 Location: Staffordshire Moorlands Posts: 7,924 Thanks: 533 Thanked 1,178 Times in 920 Posts	The 75 it's coming from is a 177 2.5 auto, which has been doing sterling work driving me about over the last few weeks, so he shouldn't notice a massive difference, hopefully! __________________ 1967 Rover 2000 Automatic 1969 Rover 3500 Series One 1979 Scimitar GTE 2013 Mercedes SLK250 CDI

27th August 2015, 17:10	#8
marinabrian MG ZT Join Date: Jan 2011 Location: Newcastle Upon Tyne Posts: 20,151 Thanks: 3,565 Thanked 10,837 Times in 5,718 Posts	Colin 2diesels has a good 2.5 KV6 engine Frazer, and I bet it won't cost the earth either Brian

14th October 2015, 00:40	#9
Jules This is my second home ZT 260 SE Twilight and 10 other 75 ZT's :O Join Date: Jan 2007 Location: Conwy NORTH WALES Posts: 11,094 Thanks: 512 Thanked 1,116 Times in 763 Posts	Coolant header tank still pressurised the next day. Thread revival ! Frazzle you got to the bottom of this yet? I've had 4 cases of this with 2.5 KV6's this year alone. 2 are here & the other 2 got scrapped by their owners due to cost. Brian has Colin still got that engine if Frazzle doesn't want it? Suspected cracked heads seem to be rearing their ugly heads although I've not seen one in the flesh yet. Also is it even or odd bank head which fail the most I wonder?! The front head is going to be subjected to wider temp ranges than the rear head for obvious reasons ie blasted with cooler air on the move and when stationary the fan cutting in and out will extend the temp range wider than the rear head. On the other hand the rear head could run hotter because of it's position although in theory it shouldn't if water circulation is operating correctly. There doesn't seem to be much evidence at present as to which head is more likely to crack. It may not be due to cracks but aluminium may be going porous? The more cases we can document of KV6 pressurising, the more we can understand the causes and cures Jules __________________ [SIGPIC][/SIGPIC] Newbies do now!! 1. Plenum drains..all 3 or 4 year dependent 2. Cooling fan..All speeds functioning 3. Bonnet cable divider block

14th October 2015, 08:30	#10
directstep Loves to post MG ZT 190+ Join Date: Aug 2009 Location: Bristol Posts: 398 Thanks: 109 Thanked 51 Times in 45 Posts	Solely based on my own experiences - I'd plump for dropped/leaking Liners.....