XJ81 Hydraulic Front Engine Mountings
 

I need to change these on my car as the engine dips down under braking.
I assume they are not repairable??
It became apparent as alternator belt tension bracket hits the anti-roll bar under braking.
Also the fan catches the the shroud/air duct.

Has anyone changed these?
There appear to be two studs at the top which may mean lowering the subframe to allow removal.
There also seems to be a Torx bolt accessible from below the subframe.

Any tips welcome including the cheapest source of new ones in the UK.

Thanks

Charlie

I know very little (next to nothing) about the two 12 cylinder front engine mounts but the single rear one I believe is the same on the 6 cylinder.

If that one (the 'transmission' mount) is broken or has worn out springs/bushes it will allow the engine to move excessively.

I have heard that if it does move that much, the fan CAN contact the shroud ..maybe it's worth a check?

Larry

XJ81 motor mounts
 

The last time I replaced the motor mounts on my 1994 XJ12 a few years ago I was told by the US Jaguar wholesale place that I might have gotten the last two available mounts as they were no longer being produced.

The front mounts on the V12 are very special and have a hydraulic element to them and they collapse. Looking at another posting on here by HarpersMuse who has done a wonderful job resurrecting an XJ81 the photos on his post show a new mount with an old one and there is at least 1.25" difference in height!
I have been offered a second hand pair but all the challenges involved in changing them and the fact the failure is probably age rather than mileage related new ones is probably the only option. Cost hurts badly though!

I will check the rear transmission mount too as I changed that on my V12 X300/305 as it caused a rattle. I have now sold that one.
Regards
Charlie

I’m dealing with rear engine/transmission mount rebuild now on my 1996 XJ12. The front mounts IIRC are the same for the XJ81, but last time I checked Jaguar Heritage Parts, they were listing for something like $600+ each.

Nick

That's crazy :)

.... I wonder if one could make a new mount out of poured/cured rubber and studs/sockets like a standard motor mount versus the complex hydraulic OEM solution? Or perhaps one could modify another XJ40 mount to fit?


It may not be as uber-isolating as the OEM mount, but it could work.

So I’ll correct the record with current information.

Jaguar part MMD7500AA covers the XJ81 and X305. Currently 355 Euros or about $400 USD each at current exchange rates. Still available.

I’d imagine the hydraulic/rubber elements could possibly be rebuild by a competent shop?

-Nick

I know people who have poured their own motor mounts from polyurethane, took a while to set up but worked well.(and was certainly more affordable!!)

Larry

Thanks for all the replies. I have changed the front mounts today. It took 7 hours. Even with a two post lift and a proper engine support beam they are a real fiddle to change but it can be done without dropping the subframe. The drivers side on a UK car is much more difficult as you have the alternator, steering column and the power steering pipes to contend with. Getting the old mounts out was relatively easy as they were both in two pieces so needed changing anyway. Getting the new ones in was very tricky. Much altering of the lifting beam needed. Oh and before you start you have to remove the heat shields which are on two 5 mm studs. They have been refitted fully polished to help reflect the heat away. The difficult side I managed to refit without removing the alternator but detached the power steering pipe bracket held on my two of the 8 mm sump retaining bolts. As I say very tricky and lots of skin abrasions to show for it. No room for long sleeves or gloves!

Ok so engine mounts replaced. Gearbox rear mount parts on order to be with me tomorrow as the yellow sponge bit had disintegrated. As of now there is still a clonk under braking and I think changing the gearbox mount may help but I suspect there is another problem still yet to be found. I will update when I have the final solution.

Final solution
It was the sub frame mounts the clonk only occurred under forward braking and not in reverse.
Mounts changed.

Undo nuts on top of front shock absorbers such that nut still has full engagement on thread (Make sure you prevent stud turning as you remove nyloc nut as sometimes the rod can unscrew inside the shock absorber and then you need a new one!)
Lift car up on two post lift
Fit engine lift beam across inner wings
Using 50mm ratchet straps fed carefully up each side of the front of the engine hooked to anti-roll bar avoiding crushing any wiring or pipes.
Tighten ratchet straps to support sub frame and engine
Fit spring compressors to each side to prevent suspension opening up and damaging shock absorber. (You really need two Jaguar tools for this but I used two hooked spring compressors which were ok but difficult to fit and they only compress on one side but it worked)
I made an X300 spring compressor out of M16 threaded bar when I changed the front springs on my XJ Sport but I lent it someone and it never was returned.
Place trolley jack under front sub frame and take the weight just enough to be able to release the tension on the ratchet straps (Remember the car is still in the air on the two post lift so you can only jack enough to release the tension on the straps)
Remove front wheels
Undo two top bolts and four M8 x 20mm bolts attaching mount to body and sub frame each side. The eight lower bolts can be removed working through the wheel arch but it is very fiddly.
Luckily on an XJ40/XJ81 these are hex head bolts. On the X300 they are torx drive which would probably necessitate dropping the sub frame to change the mounts as access to the engine side bolts is very limited
Release ratchet straps but make sure they still will hold if jack was to fail or lower unexpectedly (have a couple of turns around the ratchet tensioner)
Lower jack enough to remove sub frame mounts
Fit new mounts to sub frame
Using trolley jack raise sub frame to engage upper cones into chassis rails ensuring shock absorber top studs go through the holes in the inner wing if they have come out
You may need to pull sub frame back using ratchet straps attached to eyes adjacent to rear sub frame mount (I did)
With careful manipulation of the jack and pinch bars you can line up the cones to get the upper bolts in
Leave sub frame supporting ratchet straps in place
Remove the other two ratchet straps if you needed to pull sub frame back
Re fit front wheels
Lower & REMOVE trolley jack
Lower lift carefully checking top shock absorber stud goes back through inner wing and stepped washer seats correctly and lower lift enough to refit top washer assembly & nyloc nut. Then fully tighten both top nuts.
Lift car on two post lift and remove spring compressors
Lower car to ground and remove ratchet straps supporting sub frame and engine
Remove engine lift beam

Only change to this method would be to remove front shock absorbers first.

Hi Atco,

Thank you for reporting back with the solution to your clunk. From your description, I gather it was the "Vee mountings" that you replaced. To give other members a visual aid, the Vee mountings are part 3 in the diagram below. The rear fulcrum mounting bushes are part 2.

https://cimg6.ibsrv.net/gimg/www.jag...d981520aca.png


Cheers,

Don