JD 6420S head gasket advise please.

traineefarmer

Member
Mixed Farmer
Location
Mid Norfolk
Hi everyone.

Our 2007 6420S has blown its head gasket and we are in the process of repairing. The engine is stripped and there is a hairline crack from No1 cylinder into the water jacket. No3 and 4 are also looking like they would have failed if left much longer.

I've not yet checked the head for flatness or liner damage, but I'm hoping that we have caught it soon enough.

The engine has done around 7000hrs.

I have read plenty of threads on here and elsewhere about JD head gaskets, but I was hoping for some advise to clarify a couple of points. Obviously I need new head bolts, which I understand to have a different torque requirement, but I have also read that Claas offer a higher spec MLS gasket than JD do.

What is the collective knowledge of TFF's advise? JD bolts plus Claas gasket? Skim head as best practice?

Thanks in advance, I look forward to hearing which tractor I should have bought instead.....:ROFLMAO:
 
I'm sure someone will correct me if wrong but I think the Claas gasket is 6 cylinder only?
However, skim head a must and also check block for flatness. New bolts a good idea, but I'm sure you only needed to replace if flange headed and not if with separate washers. Any old gasket will do if the first one made 7000hrs then I'm sure the next one will too if done correctly
 

Timbo

Member
Location
Gods County
I'm sure someone will correct me if wrong but I think the Claas gasket is 6 cylinder only?
However, skim head a must and also check block for flatness. New bolts a good idea, but I'm sure you only needed to replace if flange headed and not if with separate washers. Any old gasket will do if the first one made 7000hrs then I'm sure the next one will too if done correctly

Check block for flatness and check none of the liners have sunk.
Have head checked & a skim as necessary, even if it's flat - a facing skim will clean it up.
Replace the headbolts - they aren't re-useable - current bolts are more "stretchy" n clamp the head better.
Clean out the block threads & make sure no oil or coolant remains in them.
Get a headset & gaskets. The MLS HG is only for the 6 cylinders I believe. The JD set comes with, bizarely, a sump gasket - vapormatic set you can mix n match.
Injectors will have to come out to skim head, keep them in order and do not be tempted to clean the tips., Replace the O rings, copper washers and the transfer tubes. Expensive yes, but they willl leak if you dont.
If you have removed the exhaust manifold with no broken bolts, well done, if not, get a new set as they are also stretch bolts. also 4 x gaskets.

Finally observe all the tightening torques to the letter -esp the head bolts . .
 

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