Cylinder head leak

(Bram Meewisse) #1

Hi Jag-lovers,

I’m having a strange problem with my recently rebuild engine. It’s the original cylinder-head of my S2 1969 cabrio. The car has driven around 200 miles since restoration. There were no problems in the first miles but right now a very small leak has been seen in the casting of the aluminium cylinder-head. Quit typical is that the leak is right beside a coolant core bolt, but it is not coming from the bolt or copper washer. The coolant is coming really from the aluminium casting. See photo’s below:

So my biggest worry is that my cylinder-head is cracked. Is this likely or would it be a corrosion problem? Or maybe something else? All suggestions are welcome!

(Ian) #2

Look’s like a pin hole to me in the casting , but what to do ?

If you know a good welder that can work with alloy , should be able to clean the hole out a little , and weld it up !

Save taking the head off !

Looking at the blow up pic , it looks a bit crusty to me , may be rotten alloy !

The hole could be going sideways in to the thread , worth taking the bolt out and having a look !

Look’s like a nice rebuild , lots of time spent on it , last thing you want is to strip it all down , there is some good Epoxy resins on the market now , worth a try , clean out with a drill bit , dry and apply resin , a little silver paint , you would never know , at least you could enjoy the car , may be a long term fix , not a great deal of pressure in the water system

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(Bram Meewisse) #3

Thanks Residentalien,

First i will try to take the bolt out. Might it be an idea to drill the pinhole out and drill a hole for threat tapping. Then screw an aluminium rod in the hole and hammer it down with a punch?

(Paul Wigton) #4

Before all other methods, I would try a heavy duty block sealer, like NAPA’s Heavy Duty Block Sealant.

I don’t trust, nor have I seen them work for long, the ones that advertise, “Just put in the coolant, and drive.”

(Rob Reilly) #5

Is that hex head core plug steel? The plugs in my 120 are brass.
Many of us have dealt with corrosion in the head around the holes leading to the block. TIG welding with argon or helium shielding gas (aka heliarc) is the only way to go with this problem.
You want to find a welder that is familiar with welding cast aluminum and has a portable rig to come to your place to do the job.
Drain the radiator.
Remove the core plug and maybe you can get a mirror or bore scope camera in there to see how much corrosion is on the back side.
Leave the spark plugs or some dummy 14mm plugs in to prevent anything dropping down the holes. Get the plug wires and lifting strap out of the way.
Remove the bonnet so the welder has plenty of elbow room to work and can get in a comfortable position.
Clean the area with a wire brush attachment in a drill.
Use a die grinder to grind away all corroded aluminum. You want to get down to good clean newly exposed metal.
Vacuum it all out.
It is best if the welder can begin work within an hour of this grinding.
If the sealing surface of the core plug gets distorted, you can use a hand file on it to get it flat and smooth again. Use a new copper washer on the plug.

(Ian) #6

Worth a try Meewisse , you can get very small copper grub screws , if it was me , I would try the easy way first ,

Take the nut out first and have a look , you can get very small cam’s , like 5-8mm that fit on your phone , to see whats what in the hole first !

If you can’t see much , drill a small hole make sure it’s dry then resin it up , if that don’t work tap it and screw in a grub screw ,

If that don’t work , like said get a welder in ,

You should be ok if it is just a pin hole , you just don’t know until you start , good luck

J-B is what I use on jobs like this !

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(Ian) #7

Or , worth a try !!

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(69 FHC ) #8

I love JB weld and buy it in industrial quantities, packages of 2 - 5 oz. tubes.

They also make this stuff which is for higher heat environments. I’d try it.

(Bram Meewisse) #9

Thanks, This is plan A for now! Plan B is tig-welding.

I will keep you guys up to date

((Paul)) #10

Yes, please do.
I absolutely hate botch jobs, as we all here do, but jb weld is definitely something i’d entertain without reservation nor would it offend my perfectionist sensibilities…fwiw.

Personally, I’d suggest not allowing yourself to be come paranoid or unnecessarily concerned.
Frankly, i don’t see anything here.

From the photo at slight distance reveals apparent staining from past leakage, that is all.

If it were me, #1 i would properly clean up that entire valley prior to doing anything with a brass wire wheel brush.

With these cars in particular, cleanliness is indeed godliness, and it is a prescription which no doubt has saved me many headaches and unnecessary work over the years with all of my old jaguars having never let me down.

As a final bit of reassurance, my S1 XJ6 had the most extreme corrosion from sitting than i have ever witnessed.

The internals of block and water pump looked as if they were left aboard a sinken ship 100yrs.

Despite of course need to replace everything, the block cleaned up perfectly, and despite some inlet port corrosion, the head was perfectly fine.

I supose my point is, from my experience all these years with all these old jaguars i’ve brought back from dead, they’ve never ceased to amaze me.

So try and stay optimistic! :slight_smile:

(Bram Meewisse) #11

Soooo. Plan A and B are both not not applicable…

Things went a bit different than expected. Started with taking the bonnet off, and than the hex bolt. So far so good. But then i started poking with a screwdriver en than this happened.

So I think this head is gone? What are your opinion?

(Ian) #12

Ouch , look for another head , the rest of it may be going the same way !!

(69 FHC ) #13

I’d agree with Ian. Find a sound used head, polish the old one and hang it on the wall as art.

(Paul M. Novak) #14

I agree with the others. You will have to remove the head anyway to inspect for other damage but I don’t believe that this is can be economically repaired or trusted.

Just in case you are not aware, you can use the cylinder head from a Series III 4.2L XJ6 to replace the one you have. I replaced the original head on my 1969 E-Type Series 2 FHC several years ago with one from a Series III 1985 XJ6 as a temporary measure until I got the original head rebuilt. The original 4.2L engine continues to run fine with the Series III XJ6 head and cam shaft covers.


(Bram Meewisse) #15

Thanks, that might be an option.

I think you have to adjust the XJ6 cilinderhead a bit to make it work? Does the XJ6 SIII not have bigger exhaust valves? Maybe blocking some coolant holes?

Another option i have is using the Big Valve Military head?.
I know somebody that still have these new in the crate. But I don’t like the fact that it’s not an E-type head.

(Paul M. Novak) #16

It was about 10 years ago when I removed the original cylinder head from my 1969 E-Type FHC and replaced it temporarily with one I removed from the engine of my 1985 XJ6 Vanden Plas parts car. I was having an intermittent misfire problem at the time and did the cylinder head swap primarily as a trouble shooting technique to determine conclusively the reason for the misfire. I suspected weak valve springs and confirmed that when the misfires disappeared completely with the replacement head.

The details of the cylinder head swap escape me but there wasn’t much to it and I got my E-Type back on the road again in a few days. This much shorter than a rebuild would taken because my inspection showed that the original head was going to need a lot of work on the valve guides and valve seats.

I had to use the XJ6 cam covers instead of the E-Type ones, and there were a few other little things to do, but nothing major. I am sure that the Jag-Lovers archives would have a lot of posts about this type of cylinder head swap and others will likely chime in about the details.

If you have a good replacement cylinder head handy, like I did, you might try this as a temporary fix until you can source a proper replacement head. However, sometimes temporary solutions migrate to semi-permanent ones over time. :wink:

I still have the original head and plan to get it professionally rebuilt at sometime in the future. But for now it sits on a shelf in my garage awaiting it’s turn in a never ending queue of projects on my five Jaguars. Just in case you are wondering, the original head is not for sale. Sorry.


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(David Jauch) #17

It, just as the military head, has bigger inlet valves (that should provide more top end power). The coolant passages in the rear of the head must be blocked, the later design has two extra ones. Look into a stakedown kit for the tappet guides to prevent them from coming out. The rest should fit mechanically.
The air injection porting on federal heads must be blocked, or look for a proper one (european heads have no air injection).
Must have been quite a shock.

(Ian) #18

You can fit the early cam covers to the later engines , I did this to a 1975 3.4 XJ6 Engine , I fittead in to my MK2 , as well as adding a tach drive on the back , to make it look like a 340 engine

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(Paul M. Novak) #19

You are jogging my memory a bit about my cylinder head swap. I did have to plug up the air rail ports, but I brought the air rail with me to a local mom and pop hardware store and they found a common brass household plumbing pipe plug that matched the threads perfectly. I probably spent less than $5 US on the six brass plugs.

Now regarding the coolant passages, I think that all I did (but I could be wrong about this since it was about 10 years ago) was use the correct head gasket for the 4.2L E-Type block, not the gasket for the 4.2 L Series III XJ6 head. The older block and head gasket did not have those coolant passages so the correct gasket for the block did the trick. I hope someone else can confirm that one way or the other. But that is what I recall anyway. I hope that I am right about that.

I recall that at the time how amazing it was that I could so easily and affordability swap out a 1969 E-Type 4.2L cylinder head with one from a 1985 XJ6 4.2L engine. I got the cylinder head from the parts car I had in my barn, and I had a cylinder head gasket kit on hand.


(Graham Knight) #20

That’s unfortunate. But what would cause that problem, is that dissimilar metal corrosion or is it mechanical damage from overtightening or both?