jcb 3c 2

[MrF]

For the cab oil leak, there are multiple hydraulic hoses that go up to the steering orbital valve. It might not be the valve itself, but one of those hoses chaffed or damaged in some way. To get a really good look at the area to diagnose it properly you can take the steering wheel/dash off, but you can lie on your back and look upwards. To facilitate this I just take the seat off where it bolts the top of the gearbox, same as I do for any major interior work, every job is so much easier without it getting in the way.

[Neil king]

no good I'm gonna take the head off now as its just pressurising (can of worms) hopefully not

[MrF]

My first 4/98 I could never get to seal up properly, and after replacing a liner hydrolocked it a few times but that could be liner or injector sleeve related although there was a loose oversize seat in the head and all sorts. Currently I'm running my spare engine because of various reasons, but I will get back and rebuild myself that engine properly one day as my replacement engine runs lumpy & feels out of balance...

If you do take the head off, run a flat straight edge across the block to assess it for warpage, and measure the protrusion of the liners above the block, same for flatness of head. You may be chasing someone elses un-cured issue otherwise and it doesn't cost anything to check once you have the head off. Cylinder liners come in different lip thicknesses and the replacements have to be selected according to the actual block casting, so if its been relinered badly the height might be wrong and the gasket will never seal long term.

There is a 4/98 engine manual in the download section with info, you can get by with a straight edge and feeler gauges, or a depth mic if you have one. For block flatness, if you put a light source behind a good quality steel rule, you can see by eye light if the surface deviates by a thousandth of a inch. Liner protrusion can be done with a straight edge spanning the liner lip and measure the gap to the block but its a lot easier with a depth mic.

[MrF]

If you haven't found the download section already, its a mine of great info on jcb's and many other machines. The engine service manual :- JCB 3C Leyland 38TD and 4/98NT engine service manual

I'm making the assumption you have a 4/98, but there's very little difference externally to a 38DT which was fitted to earlier mk2's. But it will matter when ordering parts. If you have a 4/98 the engine number should be prefixed 4/98 and be on the top of the block casting at the rear left as you are looking at the engine from the front. Just outside the head clamping area.
Here's the one from my mk2 engine (though the number itself is not a valid factory number, you get the idea, it should start 4.98 or 4/98 )


If you have the earlier inline injection pump in place of the dpa, be careful about which banjo bolt goes where if you strip the injection lines off. The filter head and injectors take the same size banjo bolt, but the one in the filter head has a really tiny cross hole, and if you get them mixed up, it can cause uneven fuelling and smoke and all sorts.

One last gotcha, the head gaskets have a correct way up according to the slip that came with mine. They wouldn't bother writing a slip and putting it in the packet if it didnt matter...

[dixie-normous]

Might be worth getting the head skimmed and pressure tested if the liner protrusions look ok. There are a number of things that can cause your problem as MrF says, at least once the head is tested and skimmed you can rule it out (assuming its ok) and start looking at the block/liners. The head is the easiest/cheapest place to start and you may find a skim will sort the problem

[Neil king]

so the head looks ok gonna put a straight edge on it but the gasket looks worse for wear
have order new gasket hopefully the right one
linners are all the same height

[MrF]

Yep that is a 38TD, not a 4/98, but Charnleys state the headgasket is the same after a certain model number which yours seems to be one of :-
https://www.charnleys.com/part/leyland_ ... ead-gasket
It is different when it comes to some other parts as the two engines have a different bore and stroke. Both have the liners protrude the same amount (0.08-0.15mm) though so your measurements there should be valid still.

[Neil king]

So new head gasket didn’t do the job ,ffs still pressurising system although no where near as bad , ran for an hour and retightened head bolts down but still getting pressure gonna work it this weekend and see how it performs, didn’t get head faced because all looked good with a straight edge, am I just wasting my time

[Jeremy Rowland]

So new head gasket didn’t do the job ,ffs still pressurising system although no where near as bad , ran for an hour and retightened head bolts down but still getting pressure gonna work it this weekend and see how it performs, didn’t get head faced because all looked good with a straight edge, am I just wasting my time

Have you also checked that the radiator isn't blocked as suggested by Pete?

Jeremy

[Neil king]

Will check that tomorrow but I’m pretty sure it’s not as when I drain the block and pour water in rad it flows out drain, also looks to be circulating with cap off