Head Gasket failure?

[mints53]

Hi all.

It's good to know that the new heads from Moss have been around a while, I'm impressed they have sold 700 of them. That is certainly an option for me then.

I have got my head home now, they detected a crack around no 4 spark plug, actually I could have told them that. There has always been a bit of coolant seapage there since I bought the car 12 years ago, never enough to result in any noticable coolant loss though. In a way I am encouraged that no other cracks were found. I've cleaned the area up now including inside the combustion chamber, no cracks are visible, but maybe they are too small or open up when hot. The dilemma I now have is, whether to put the head back on with a new gasket etc and hope that will fix the coolant pressurising problem and the crack issue was just a red herring, or get a new one from Moss.

Thanks again for all the advice

Mints53

[RogerH]

Hi Mints,

                  if the plug hole crack has been there for that length of time then it is not affecting the gasket blowing situation.

Have you spotted a possible cause for the blown head gasket.?

If all looks OK then I  would chance the existing head. Make sure it is torqued down correctly and re-torqued after 500 miles or so.

Put some Radweld or K-Seal in the coolant to stop the weep at the plug.

Good luck

 

Roger

[Motorsport Mickey]

Check the head for being flat before fitting, in case a skim is needed (remove the minimum - probably 10thou) at least you then know the gasket seal isn't compromised with that.

As Roger says a sealer in the water system stands a chance of sorting the crack (we've had several members running with the crack into a spark plug) and for a very fine crack K Seal works very well, it doesn't clog the other waterways in radiators or heaters.

Mick Richards 

[mints53]

Hi Roger:

That's my thinking as well, I can't see any obvious cause of a head gasket failure - only on one cylinder a less distinct ring where it sat on the liner. Interestingly the head has had inserts for the exhaust valve seats fitted so it has been off before. Not in my time and not by the previous owner, that would be no later than yr 2000.

Mints53

P.S the names Andy and I am located in north Bucks

[RogerH]

Hi Andy,

           not too many very local groups to you but Lee Valley is to the east and Nene valley to the north - nice runs in thew summer.

 

As well as a possible head skim have a look at the gasket face of the block for possible raised metal around the studs.

If the studs come out easily consider leveling the area around the holes

 

Roger

 

 

 

 

[mints53]

Hi all:

I've checked the head for flatness now, the worst case is a depression of 0.04mm between cyls 3 & 4. I can't get a 0.03mm feeler (my thinnest) in anywhere around the liner seal area. Is this OK or do I need it skimming?

Thanks for any info on this

 

Mints53

[TR 2100]

Have your head skimmed - it's a no-brainer.

I couldn't detect any deformity in my TR4 head with a straight edge and feeler gauge but,
2 blown head gaskets later, I had the head skimmed and it solved the problem.

True, I was using a race-style modified steel gasket and they are a lot less forgiving, but
I would still recommend skimming.

AlanR

[RogerH]

Hi Mints,

 the liners need 0.003 - 0.005" protrusion   (0.075 - 0.125mm) 

Any less and they may not clamp shut (water leak at the bottom)  any more and the head gasket may have problems.

 

Roger

[Motorsport Mickey]

I’m with Alan, no brainier, “ less distinct gasket impression” I don’t suppose it’s between 3 and 4 is it ? If so that’s why the head gasket blow.

Mick Richards

[mints53]

I've just got back from dropping the head off for a skim, I agree with all your comments, it is a no brainer really. And the less distinct gasket impression is indeed between 3 & 4 so hopefully it should be all good.

Cheers

[ianc]

In addition to Lea Valley and nen Valley, the Chiltern Group meets at The Peacock in a hamlet called Henton, near Chinnor, on the first Wednesday of every month i.e. this week.

A very friendly Group - now my local group since moving to Thame.  Excellent beer (served by Martin, a landlord who knows how to look after his beer) and very good food.

Ian Cornish

[mints53]

Hi All:

I've finished this head gasket change now and been out for a test run today, everything looks good.  The head was skimmed valves lapped in etc. The engine is running much sweeter, exhaust is clean. I'll get a few miles on it and recheck the head stud torques, but touch wood it's good.

Thanks for all the advice

[Ian Vincent]

On 3/4/2019 at 10:12 AM, RogerH said:

Hi Mints,

 the liners need 0.003 - 0.005" protrusion   (0.075 - 0.125mm) 

Any less and they may not clamp shut (water leak at the bottom)  any more and the head gasket may have problems.

 

Roger

Hi Roger,

Why would any more than 0.005" be a problem for the head gasket?  Yes, I can see where it might allow coolant (or oil) to leak out from the engine to the outside world but it would mean that the chance of leakage from the combustion chamber would be minimised.

Rgds Ian

[RogerH]

Hi Ian,

if the coolant/oil can escape to the outside world then it may also escape into each other - is that a good move.

TRiumph set the tolerance - I am simply a messenger.  

Roger

[Motorsport Mickey]

1 hour ago, Ian Vincent said:

Hi Roger,

Why would any more than 0.005" be a problem for the head gasket?  Yes, I can see where it might allow coolant (or oil) to leak out from the engine to the outside world but it would mean that the chance of leakage from the combustion chamber would be minimised.

Rgds Ian

Gasket clamping pressure on the surrounding non liner height area.

That Depends upon the head gasket composition, the liner height in the TR2 original workshop manual was 3 thou to 5.5 thou ( that’s a laugh, a TR owner measuring to half a thou with feeler gauges) but that’s with copper composite gaskets. Every thou up from there lessens the clamping pressure on non clamped areas.

On the steel “ double” compression ring gaskets we used in competition, with a couple of engines because I was trying some non standard “mods” I increased the liner heights to 6 thou. No problems with liner seal or on the oil and water at the other points, but they shared the steel compression ring around the holes, this counts for a lot.

If you used solid copper gaskets I would beware using more than the 5 unless you machined the gasket to take Mills ring, and/or a silver soldered  Copper wire around the liner and important seal points.

Mick Richards

[AlanG]

At the TRGB engine rebuild seminar anything between .003"/.010" was stated as being satisfactory. Not as critical as was commonly believed.

Alan.

[Motorsport Mickey]

I bow to their superior knowledge.

1987 TR Register Championship winner 4 cylinder. Engine builder and driver

1988 TR Register Championship winner 4 cylinder. Engine builder and driver.

1989 TR Register Championship winner 4 cylinder. Engine builder.

and builder of 20 plus road going engines.

Mick Richards.

[stuart]

12 hours ago, Motorsport Mickey said:

I bow to their superior knowledge.

1987 TR Register Championship winner 4 cylinder. Engine builder and driver

1988 TR Register Championship winner 4 cylinder. Engine builder and driver.

1989 TR Register Championship winner 4 cylinder. Engine builder.

and builder of 20 plus road going engines.

Mick Richards.

Stuart.