What causes head gasket failure?.

[daverclasper]

Hi. Just a general interest thing for me (not an accident waiting to happen this time Pete! 😊)

On our commonly, cast iron engines is this ever likely to happen?, E.G.,  if the gasket not been replaced ever/for a long time, not prone to overheating, antifreeze maintained, etc.

Actually, I probably don't mind a bit of reassurance, if appropriate 🙂

Cheers 

 

ast 

[NonMember]

My Vitesse developed a habit of blowing the head gasket every 18 months. The first time may have been caused by overheating (stuck on the M25 for four hours on a day like we've been having recently) and the last may have been loss of coolant (I discovered a crack in the block after that one) but I'm also suspicious that the studs and nuts weren't up to scratch. This is a Mk1 with the 3/8" UNF studs, and the washers may have been changed for insufficiently hard ones at some point. I can't definitively point to the actual cause because the crack in the block led to the acquisition of a replacement bottom end and a head refurb, reassembled with new studs and Mini type flanged nuts.

The only other head gasket failure I've had was the Spitfire, after the engine had sat in a series of damp barns for 25 years and been recommissioned without any work done (just new oil, really).

[Josef]

My Herald blew the head gasket on the M1 in Dec 2007 shortly after I got it. That will have been on since 1992 ish and since being replaced it’s given no trouble. So I suspect it was age and lack of use.

I do appreciate now that I was probably really lucky to do no more damage, there was not much in the way of coolant left when the breakdown people inspected it…

[johny]

12 hours ago, daverclasper said:

Hi. Just a general interest thing for me (not an accident waiting to happen this time Pete! 😊)

On our commonly, cast iron engines is this ever likely to happen?, E.G.,  if the gasket not been replaced ever/for a long time, not prone to overheating, antifreeze maintained, etc.

I do think the retorque of the head after a few hundred miles (and maybe even later in the engines life) is essential. On some of our engines, because of the layout of the fixings, this isnt easy and I wonder if sometimes doesnt get done...

[NonMember]

8 minutes ago, johny said:

I do think the retorque of the head after a few hundred miles (and maybe even later in the engines life) is essential.

I certainly found it to be essential on my 1850 Dolomite, where it can be done fairly easily, fortunately. The push-rod engines don't seem so bothered about it.

[68vitesse]

1 hour ago, johny said:

I do think the retorque of the head after a few hundred miles (and maybe even later in the engines life) is essential. On some of our engines, because of the layout of the fixings, this isnt easy and I wonder if sometimes doesnt get done...

As in the narrow head six cylinder engines a row of long studs easily accessible and a row of short studs that need the inlet and exhaust manifold removing. When l had to replace the head gasket on my Vitesse Mk1 2L earlier this year used NOS gasket, mini flanged nuts without washers and retorqued the head after a thousand miles.

Had more trouble with the manifold gasket which l now retorgue and have lock nuts on the two end studs.

Regards

Paul.

[Pete Lewis]

head gaskets can last as long as the car lives   what we have on  triumphs cast iron heads is soft washers and on 4 cyl and 1600/mk1  is small 3/8" dia  head studs

where the torque on the 3/8 unf nuts is higher than a std bolt  at 42 46lbft  which needs a special quality nut ( std 3/8 would be 31 lbft ) so using a std nut will just strip 

hard/ heavy duty washers are available  as removing  a nut will most likely reveal the washer face has dished under the load of the nut ( and the panting the head does with compressions)

so a retorque should replace lost torque due to washer deformation(that you cant see)  as most gasket failures happen due to the loss of clamp load and the gasket then looses it grip

and odd coolant ports or fire rings can let go 

so  yes they can last for years and yes they can fail due to the limitations above

mk2 6 cyl upped the studs to 7/16"unf and  are a better design but washers can still be a problem 

does that help you sleep easy   Ha !!!

Pete

 

[Peter Truman]

I used mini head nuts which have a built in washer

[daverclasper]

Thanks guys. It is what is is then. Defiantly not something to mess with, unless problems, especially as there appears to sometimes be issues when folk replace.   

[Pete Lewis]

Dave   when it starts raining you could always do a re torque    keeps you out of mischief   ha !

if you do ever re torqure   back the nut 1/4 to 1/2 a turn and re apply the torque  this removes any sticking of the nuts 

just do one nut at a time in sequence of the bible 

 

Pete