Leaking combustion caps

[Welderpaul]

Having some trouble here. 3 combustion caps on the side of a Perkins P3. New copper sealing washers on the original caps, leaked. Heated the washers to soften, leaked. Used Permatex copper gasket spray as suggested by @Pete. , leaked. New combustion caps, new copper washers, leaked.

Studs are as tight as I dare without snapping them.

Side of the head is machined perfectly flat so i'm at a loss. I've used Hylomar Blue on just about every other joint on the tractor and it is totally tight as a drum with no leaks on anything. Would Hylomar Blue be ok on this - it will get hot - so i have avoided using it.

There's another slight issue with combustion gas shoving the coolant out of the filler cap and diesel leaking out of the head gasket, but we'll come to that next

Thanks

 

[Ubique]

With those three issues it sounds like something is cracked or distorted and causing all of it.

 

[MattF]

Those plates don't look like they're tightened down properly?

 

[Ubique]

The plates have a boss in the middle, the ears that have the studs pass through never go flush to the mating face

 

[Welderpaul]

The plates have a boss in the middle, the ears that have the studs pass through never go flush to the mating face

Exactly that. The original ones are machined flat on the back so the entire surface sits against the block

 

[m_c]

Exactly that. The original ones are machined flat on the back so the entire surface sits against the block

And that's why it won't be reliably sealing.

 

[Welderpaul]

And that's why it won't be reliably sealing.

Why?

 

[MattF]

Exactly that. The original ones are machined flat on the back so the entire surface sits against the block

You know what the answer is there, then. If the originals worked fine & these don't, flatten the mating face so they're flat against the seal.

 

[Ubique]

Have you run a straight edge across the ports on the block? it's as very long time since I had owt to do with a P3, there's something in the back of my mind about the ports becoming distorted - can't remember why though.

 

[m_c]

Why?

If the gasket isn't being clamped between the cover and the head, then it's solely relying on the fit between the boss and the head to seal, which it won't.

Why didn't you re-use the original caps?

 

[Welderpaul]

You know what the answer is there, then. If the originals worked fine & these don't, flatten the mating face so they're flat against the seal.

The original caps leaked

 

[Ubique]

It's sort-of coming back to me - engineers blue on the block face and pass a straight edge over, if all ok, double gasket after cleaning, cleaning and cleaning.... then hand tight on each nut followed by 1/2 a turn on each one until 'F-tight'

 

[MattF]

The original caps leaked

You never mentioned that bit. The surface must be either distorted or corroded then, surely.

 

[Ubique]

If the gasket isn't being clamped between the cover and the head, then it's solely relying on the fit between the boss and the head to seal, which it won't.

Why didn't you re-use the original caps?

IIRC the copper gasket extends inwards to the mating surfaces, it's not just a peripheral gasket, despite appearances from the photos.

 

[Welderpaul]

You never mentioned that bit. The surface must be either distorted or corroded then, surely.

Nah, perfectly flat as far as the eye can tell

 

[8ob]

Had this with a p4 head I bodged fitted onto a 4203 perkins, there are two types of combustion caps,. One type the spigot of the combustion caps seats on a copper washer inside the head (no external gasket) the other type doesn't bottom out and uses an external gasket. Looks like you have the wrong caps/gasket combo, it also has a big effect on compression.

Bob

 

[Kram]

The visible part of gasket does look like its flapping about in the wind and not doing much, looks like it needs a soft spacer behind it.

Have a photo of the caps and bore disassembled?

 

[Welderpaul]

Any reason why two cylinders are sooty and one is clean?

 

[Ubique]

The clean one either has an injector weeping into it or a crack in the head or block letting coolant in / pressure out as per your first post regarding coolant system pressurisation.
The head looks pitted either side of the injector port on the 'clean' cylinder' and there looks to be something stuck to the head and gasket where the sealing ring is, close to the coolant port - is it possibly a corrosion mark from coolant passing through?

 

[Welderpaul]

The clean one either has an injector weeping into it or a crack in the head or block letting coolant in / pressure out as per your first post regarding coolant system pressurisation.
The head looks pitted either side of the injector port on the 'clean' cylinder' and there looks to be something stuck to the head and gasket where the sealing ring is, close to the coolant port - is it possibly a corrosion mark from coolant passing through?

The corresponding injector (top one here) is also clean on the end whereas the others are slightly sooty.