BX Head Gasket Failure - The Culprit

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Post by madasafish »

Jags had alloy heads from the first XK120 in 1949 or 1951 or whenever. Minis had aluminium alloy gearcases from 1959.
I had a 1981 XJ6 where the aluminium thermostat housing had welded iteslf to the holding bolts thru alloy corrosion. Lots of vinegar and 48 hour slater they separated.
The Lotus dohc engine in the 1960s Elan had an aluminium head. I had one: a great car.
IIRC the Rover P4 had an alloy head: I had a 75 and 110: great cars.. heads never went - because they were so thick!
Problems with Citroen heads are 99% due to lack of maintenance: chane antifreeze every 2-3 years, use the right type and use a 50% mixture and you should be OK.
Funnily enough BMWs use alloy heads and engines with no problems.
The Rover V8 was aluminium - a long life engine provided it was maintained.
The Triumph Stag had aluminium heads and was appallingly unreliable because of its design.
Rover K series engines have aluminium heads and suffer head gasket failure frequently due to design problems and the complexity of bleeding the cooling system (and the incompetence of many Rover dealers).
RR V8s were 100% alloy.
Generalisations about use of materials mean nowt: design and maintenance are key...imo

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Post by NiSk »

I made the mistake of pressure testing the radiator from a Volvo 740 I was repairing for a friend- the normal water pressure from the tap blew both the nasty plastic end tanks off the fragile pressed aluminium matrix in less time than I had to turn the tap off! talk about almost-good-enough design (I think its called "lean design" these days).

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Post by f00lzz »

I believe the main cause of a 'restricted flow' in the radiator has been overlooked.... modern cars (ok post mid 70's) generally use a 'crossflow' radiator wher the tubes run horizontally as opposed to vertically in older cars. The effect is similar to that in a river.... if the river stops flowing... as in switching off your engine.... then the sediment drops to the bed of the river, so after years of switching of your engine your 'river bed' gets silted up and blocks!! Oh and the reason for the change to crossflow radiators was to facilitate lower bonnet lines.

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Post by lexi »

Lots of good banter on this thread guys :lol: I feel that with the power outputs of modern diesel engines that have Cast iron block and alloy head the need for spot on maintenance is greater than ever. Does the difference in thermal transfer put greater strain on HG with the dissimilar metals? Landrover 300TDI is another engine with high failure. That engine has 115 bhp DI out of a small 2.5 cc.
and has a turbo which all adds to HEAT!. A tiny leak from a hose which is out of sight....a blocked rad or inefficient viscous fan and Bang....too late.

In contrast the Patrol I have just sold had 4.2cc with about the same hp no turbo and cast iron block and head. No prizes for guessing which engine regularly does 500k between rebuilds. Similarly the petrol version of this engine has head issues........and it is alloy

The demand for higher power from smaller engines with improved emissions is something the manufacturers must pursue due to The Requirements Of The Marketplace. Thank goodness we can still choose old school technology with an older car. Takes me back to my youth trudging round these scrapyards :lol:

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Re: BX Head Gasket Failure - The Culprit

Post by Gregg1100 »

Another reason is a blocked bypass pipe--goes from rad to thermostat housing

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Re: BX Head Gasket Failure - The Culprit

Post by colin324 »

As said before, it's the antifreeze mix that is often to blame. Antifreeze doesn't just stop the water freezing, it also is a corrosion inhibitor. I worked on a XK150 engine rebuild once - the thermostat housing was paper thin because the owner kept it in a warm garage and only used it in the summer. The aluminium had corroded so badly we had to get another one made - expensive and time consuming. A lot of people will just top up the cooling system with water if the level drops, gradually dilluting the mix further so it doesn't inhibit corrosion any more.

A lot of the changes made are to reduce weight and improve fuel efficiency. The old brass/copper cored rads weighed a ton, admittedly they rarely failed. Now most rads are aluminium core and plastic side tanks. Cheaper and lighter, but different expansion coefficients - just a leak waiting to happen.

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Re: BX Head Gasket Failure - The Culprit

Post by Citroen c4 vt »

How do you know when the head gasket has gone I have no trouble starting my car and it never over heats, yet I have mechanic telling me it needs to be replaced is there any other reasons why he would say that’s and if it does need replacing how much does it cost to replace pets and labour? Thanks

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Re: BX Head Gasket Failure - The Culprit

Post by Gibbo2286 »

If it doesn't overheat or need frequent top ups then I'd guess you have a scammer after your cash.

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Re: BX Head Gasket Failure - The Culprit

Post by white exec »

Would suggest starting a new thread for this one, if needed - this BX thread is now 8+ years old.