Super Major water leak between head and block.

[liam]

Hi All
During the summer I rebuilt the engine on my np super major .I had the head skimmed and fitted new pistons and liners.Lately I have noticed a slight leak between the head and block on the lh side .It is only afew drops ,it is not noticable in the radiator .The head is torqued properly and the liner protusion is correct.I had ran the engine for about 2 hours and retorqued the head to 95 pounds .The only thing ican think i can think is the engine is not bedded in yet ,it has not got hot and done no real work yet,Any advice .Thank in advance.

[BearCreek Majors]

Hey liam, I had the same problem with my Super Major when I rebuilt it. After I had everything together and dumped the antifreeze in it, it came oozing out between the head and the block. I pulled the head back off, the gasket was good so I checked the head and the block with a straight edge and found a low spot in the block. The liners to the head had a good seal and the area that was leaking was only for the coolant so I applied some RTV/silicone sealant to the head gasket just around the coolant passages, you don’t want it around the liner seal area, this fixed the problem.
If your leak is minor I would suggest trying some coolant system sealer first.

Pat

[henk]

Liam,

Make sure the bolts are running smoothly with clean outer and inner threats. If not you will have the wrong torque and the head will not be tightened flat and right.

[liam]

Thanks for the replies Pat and Henk .I cleaned all the threads on the head bolts and the holes in the block during the rebuild so i am pretty sure they are ok . I think I will get a new head gasket and use a little silicon sealer along the water channels during assembly as you say Pat.That is the only leak so hopefully it should be an easy fix.Thanks fellas for your help .Liam.

[August]

Antifreeze leaking is quite normal in major engine after rebuilding. I had same problem with my Super Major as well. I put 2 bottles FORTE radiator stop leak into the radiator, then retightening for the head bolts and valve adjusting. After those actions and a hour running everything was ok. Tightening torque for head bolts is 120 Nm.

Kind regards,
Paavo

[Brian]

Having reconditioned, overhauled and replaced cylinder heads on many hundreds of these engine in the past forty odd years, I have never known leakage from the cylinder head gasket as described.

It seems to becoming a problem area now so I would feel that something has changed.

In the dealerships at that time we used a copper/asbestos gasket, only the NP Super had a Klinger type composite gasket. Both these were thicker than replacement gaskets I have seen today.

The head rests on the step on the tops of the liners and the liners protrude above the block surface between 0.002" and 0.004". If a replacement gasket is marginally thinner than the original it might not be pressed hard enough to seal successfully, around the water jacket holes, although it may seal the cylinder/head interface. My fear would be that if it leaks antifreeze externally, it can also leak into the oil galleries between the head and block.

A sealant like "Hylomar" can be used but do not use instant gasket or something like Hermatite Red, which could prove to be too thick.

This is another reason why you do not use a gasket that has been fitted and torqued down previously. Every time you fit a head it should be with a new gasket.

Torque down the bolts cold first and then hot to 85-90 ft lbs, if the bolt is marked "100" and 75-80 ft lbs if the bolt is marked "Bees" or "Ribes".

Always check the bolts before re-using for any "thinning" between the threaded area and the plain shank. If "thinning" is seen then the bolt should be replaced.

Always make sure the holes in the block are clean and dry. I have seen the bolt holes on the outside of the block break because of trapped oil when the head is pulled down.

I replaced the head on Henrietta using a thin composite gasket and have had no problems with seepage or leaking, however she has the flat topped liners.

[August]

Thanks Brian for your advise!
Perhaps a problem in my case is replacement gasket (Sparex), it is too thin? On the other hand the dimension that you mentioned is maximum 0,004". It doesn't leak now, but maybe I have to replace the gasket by better one some day.

[Pavel]

Just to add a little more about Hylomar gasket cement which I've used on many makes of engine -- including the head of my SMD [no leaks after 2 years].
The Universal Blue is excellent stuff and marketed in squeeze tubes and spray cans [the latter recommended for head gaskets]. In fact Hylomar was the answer to notoriously regular oil and water leaks on early 1750 and 2L Alfa Romeo cylinder heads.
Whilst Hylomar make the cement themselves, there are others, such as Permatex, that make it under licence.
It can be used on all gaskets and is also a good substitute for Loctite Threadseal. Rolls Royce still use it on their jet engines -- amongst other Hylomar products.
Pavel

[Brian]

That is the stuff Pavel, we used it on the "X" and "Y" series which had a problem with oil leakage under the exhaust manifold.