New to this forum and to L322s, so please be gentle! I have acquired a 2006 4.2 Supercharged, which has covered approx 70K miles.

I have no classic symptoms of a blown head gasket problem, but do have a slight pressure remaining in the coolant expansion reservoir even after leaving to cool for 24 hours plus. I thought I could smell exhaust when I removed the cap. So, I asked my local independent mech to carry out a block test for exhaust gasses in the coolant, the Blue solution became Green (but not Yellow as expected for a petrol), indicating the presence of exhaust gases.

The car drives perfectly well at all speeds including motorway runs, no coolant loss, no oil in coolant, no coolant in oil, no mayo on dipstick or oil filler cap, no misfire, just a slight fume whiff and lowish pressure retention in the coolant reservoir.

My independent is convinced it is not head gaskets, I am not convinced it isn't, I was outvoted 3 to 1, so I am at a loss and now looking for kind help and advice. Thank you.

Voguevague

I am not sure what the results of that sniff test mean but I would tend to side with your mechanic that it is not a head gasket. I don't think a bit of residual pressure is that unusual and you are not showing any other symptoms of a head gasket so I would be inclined to just enjoy the car but keep an eye on the coolant level.

Not sure if this is much help to you but it's all I have. Maybe some of the other regulars might chime in with other suggestions.

Good luck mate. Current Cars:
MY11 5.0 SC Stornoway - sold
MY06 TD6 Zambezi - sold
1997 BMW E36 M3 Evolution Convertible Estoril

Thanks Mark for this reply, really helpful and somewhat reassuring that you agree with my trusted independent.

As you can imagine, I want to enjoy the vehicle but have this niggle that something is amiss, I'm not sure where else traces of hydrocarbons can derive from and end up in the coolant as gases, except the head gasket, but I am no expert on the Supercharged engine.

Could be if it ain't broke don't fix, but I am wondering if it is a head gasket breach in the early stages , then should I use one of the many liquid products to mitigate. I see these leak-stop type preparations which may have fantastic manufacturer claims, but often quite opposite user reviews, have you thoughts here.

Thanks and regards, Keith.

Does the 5.0 have an oil cooler? I never checked mine. If it has a small leak maybe that could be a possible source?

When I had suspected head gasket failure I had the sniff test done and like yours came back clear.

My symptoms were excessive pressure in the expansion tank leading to pressure blow off and soaking the underside of the bonnet. It turned out to be a blocked radiator and changing it out cleared all of the problems.

My reason for posting is that I was told by many mechanics that if you have residual pressure in the system after leaving it overnight etc, then you do not have a blown head gasket. If you did have a blown head gasket then all of that pressure that had built up would eventually bleed away through the faulty head gasket and leave you with no pressure in the system.

So I’m always happy when I leave the Range Rover for a couple of days and undo the expansion tank cap and hear a hiss of pressure escaping  ______________________________
Simon
______________________________

Range Rover Classic 3.5 efi - Gone
Range Rover Classic 3.9 efi - Gone
Range Rover Classic 4.2 LSE - Sadly gone
Land Rover 110 3.5 - Gone
Range Rover P38a 4.0 SE - Pleased it's gone
Range Rover P38a 2.5 DHSE - Just sold
Range Rover L322 4.4 v8 Petrol - Current

Don't be tempted by miracle cure additives - the myriad of tiny galleries that exist in modern engines (so I am told by grown ups ) are at risk of being blocked by them. Bish.

2005 110 TD5 CSW
2011 TDV8 Vogue SE (gone)

^^^^
+1

This is what I found in my radiator when I took it off.

yak,

[quote="axe"]Does the 5.0 have an oil cooler? I never checked mine. If it has a small leak maybe that could be a possible source?[/quote


Mine is a 4.2 which I believe on reading has the LR015152 Engine Oil Cooler, not sure what the 5.0 uses.

I have considered the possibility of cross contamination between the oil cooler and coolant but would expect to see some flecks of engine oil in the coolant reservoir, these are not there (yet?).

My knowledge of the 4.2 coolant system plumbing and interconnects is very limited, but I would be interested to know how the supercharger itself is cooled if at all.

I am looking for any possibility of mixing hydrocarbons with coolant existing, apart from the head gasket or any other points of close communication which gases could breach.

bishbosh10 wrote:

Don't be tempted by miracle cure additives - the myriad of tiny galleries that exist in modern engines (so I am told by grown ups ) are at risk of being blocked by them.

UK Marine wrote:

When I had suspected head gasket failure I had the sniff test done and like yours came back clear.

My symptoms were excessive pressure in the expansion tank leading to pressure blow off and soaking the underside of the bonnet. It turned out to be a blocked radiator and changing it out cleared all of the problems.

My reason for posting is that I was told by many mechanics that if you have residual pressure in the system after leaving it overnight etc, then you do not have a blown head gasket. If you did have a blown head gasket then all of that pressure that had built up would eventually bleed away through the faulty head gasket and leave you with no pressure in the system.

So I’m always happy when I leave the Range Rover for a couple of days and undo the expansion tank cap and hear a hiss of pressure escaping

[quote="UK Marine"]When I had suspected head gasket failure I had the sniff test done and like yours came back clear.



Simon,

My test actually came back 'positive' (?) in that the solution went GREEN.

If negative it should have stayed BLUE.

Ironically, GREEN is a positive for diesel engines. mine being a petrol should have gone to YELLOW, so all a bit inconclusive.

On smelling the unpressurised coolant cold yesterday it still smells gassy. I will drain and change out, then pluck up courage to retest.

Keith

Voguevague wrote:

Mine is a 4.2 which I believe on reading has the LR015152 Engine Oil Cooler, not sure what the 5.0 uses.

I have considered the possibility of cross contamination between the oil cooler and coolant but would expect to see some flecks of engine oil in the coolant reservoir, these are not there (yet?).

My knowledge of the 4.2 coolant system plumbing and interconnects is very limited, but I would be interested to know how the supercharger itself is cooled if at all.

I am looking for any possibility of mixing hydrocarbons with coolant existing, apart from the head gasket or any other points of close communication which gases could breach.