Actually, the pressure Evans has is very near zero, or otherwise 'ambient'. At full operating temperature you really can remove the coolant cap with no bad things happening. I do that on my P/S Mustang to freak people out.

 

This is the mess of coolant residue inside the bellhousing. The torque converter side is exactly the same. It must the concentrate from litres of evaporated coolant.



The gearbox was extremely difficult to separate from the engine as Jaguar decided to use "external" locating dowels high on either side in an inaccessible place rather than the "internal" dowels I've found on every other gearbox I've ever removed. Steel dowels open to the atmosphere in an aluminium casting was never going to be a good idea!

The biggest problem is that removing the gearbox turned out to be a waste of time, apart from the fact that I've been able to snip the end off the duckbill with a pair of scissors.

When I looked into those three open holes in the casting at the very top above the core plugs and oil gallery bung with a torch, it's obvious that the coolant is leaking into the bottom of the V between the cylinder banks and the running out of the lowest point of the two holes on either side and then running down over the core plugs before accumulating in the bottom of the bellhousing and then being splashed around the entire space by the starter ring gear. When I first saw the pink core plugs I thought that the issue was as I believed, but cleaning them up before I took the photo showed no sign of any leakage.

My new theory is that a coolant line in the valley must be leaking. I know these are a likely leak spot on these car but everything I have read and seen suggests that coolant leaks in the valley run down over the outside of the bellhousing and are easily visible at the back / front of the engine when you look down inside the engine bay. My car has no coolant leaks visible from above. The only way to observe the leak is the remove the rubber bungs in the bottom of the bellhousing and witness the lake of coolant in there.

Until I remove the intake manifold, I won't be able to understand why my XK leaks its coolant into the bellhousing rather than down the outside. Presumable there is a lower plate across the valley which is supposed to be sealed but in my car is allowing coolant to pass through and down into the very bottom of the valley. I can't understand why this is not a lot more common but I seem to have fallen victim to being the first to record this particular fault. ☹

Any thoughts on this turn of events would be most welcome. I'll report back once I have the inlet manifold off.

Richard

 

Hi Richard,

I am following your progress with great interest!

Regarding the locating dowels, the 6HP gearboxes used on BMWs are set up the same way, so I think we have to blame ZF rather than Jaguar. I clean them up and wipe a little aluminum-based anti-seize compound on them before reassembly to help myself or the next tech who has to pull the transmission.

Regarding your coolant leak, looking at the parts diagram it must be the "Engine Cover" (Part 1 in the diagram), the molded plastic plug that fits into the top of the block:





I couldn't remember having seen this plug until I pulled up a photo of the block from an ebay listing, and there it is:





I'll be very curious to know what you find when you get the intake manifold off. Aside from a few fiddly fasteners, its really not a difficult job on the normally-aspirated engines. Just a lot of brittle plastic parts to deal with. I recommend replacing every seal and O-ring you can to reduce unmetered air leaks that commonly develop with age.

Cheers,

Don

 

Thanks very much Don. I assumed that the dowel design was a Jaguar feature as it seems so unusual but if BMW's are the same then I think you are correct about it being a ZF thing. If only Jaguar had used a little anti-seize on the dowels. It must have taken me two days to persuade the flange to separate and when it finally went it was like a gun going off. It's not the kind of sound that you want to hear from expensive metal parts!

Your rubber bung theory is fascinating. I wonder why Jaguar did not simply make that plate a solid part of the casting of the block? The rubber bung seems to serve no useful purpose unless there is something underneath it that needs to be accessed but I've no idea what that might be. Anyway, the fact that there is a bung there does mean that there is a way for leaking coolant to find it's way directly into the bellhousing without making any appearance on the outside of the block or bellhousing. It's just my bad fortune that it doesn't seem to have happened to anyone else. ☹

I'll update this thread with my findings. Hopefully, it could prevent someone else in future wasting a lot of time or money.

A small point to help anyone else is that the Jaguar workshop manual states that you need to remove the two securing clips holding the main loom cable which runs down the back of the engine to the gearbox port once you have started to drop the gearbox but before the cable starts to become stretched. My car had three clips so I removed the two I could actually see from underneath but missed the third one until it was almost too late!

Richard

 

My assumption is that either the recess that is covered by the rubber bung was required so the sand/clay core could extend inside the recess to form some important shape in that part of the block during casting, or the recess is there as a mass-saving measure, since these days every gram matters.

 

The results are in! The photos shown the coolant line which feeds the throttle body and the EGR valve is leaking adjacent to the plastic blanking plate. It appears to be the only coolant hose which runs in the valley so it's a pity that Jaguar did not design it so it runs outside. I haven't removed the blanking plate yet as I need to vacuum out all the crud first but that is clearly where the the coolant has entered the bellhousing.

I don't understand why the coolant has not run down to the low valleys on either side and then spilled out over the outside of the bellhousing. It seems to have followed the higher route which is not what liquids normally do but it is what it is. I'm going to try and clean everything up as much as possible and then seal the blanking plate with RTV sealant to try and prevent the bellhousing filling with coolant ever again.



I hope this thread helps someone in the future.

Richard

 

New genuine Jaguar hose is now fitted and everything cleaned up. The hose only cost £15 / $20. It's a pity that such a cheap part can cause so much trouble.

Richard

 

Just a thought, maybe the hole was for smugglers to carry their contraband? Not an easy place to search!

 

Dude, you are SO luck you don't have an /R to do that on. Just the intercooler removal takes a few painful hours. Probably down to two with some practice.

 

Just a final thought on this thread which points out something I had never thought about before.

Firstly, although I've removed many manual gearboxes and have drained and filled many autoboxes, I have never removed an auto box before.

According to the manual, the ZF box fitted to the 4.2 XK holds 9.5 litres of fluid in total and holds 6.0 litres if you exclude the torque converter. Even though I had removed the gearbox, I decided not to remove the torque converter as that would usually involve changing the oil seal and I already had to do the diff main seal so was trying to keep the work to a minimum.

Anyway, as I already had the gearbox in an engine crane, it was easy for me to remove the drain plug and run out the old fluid. However, I then decided to tip the box slightly towards the drain plug just to make sure that I had fully drained the pan and, guess what, another couple of litres came flooding out. I didn't really think about it at the time but this was the torque converter draining out into the sump. If I tipped it a few more degrees I reckon I could have virtually drained the torque converter without ever removing it.

The refill kit I bought included 7 litres of LifeGuard 6, just to be on the safe side, but once I realised what I had done, I bought another couple of litres and used another whole litre to refill the box to the correct level with the engine running. This is a much better exchange rate of old fluid for new than I have ever achieved before.

What is the lesson to be drawn? Well, in future, when I'm draining the fluid with the gearbox in the car, I will drop the back end of the car with the front wheels on stands and get a load more old fluid out.

Richard

 

Hi Richard,

It sounds like you're close to getting the car back on the road. Good work!

Did you set your transmission fluid level with the fluid at 40 degrees Centigrade? If the fluid gets too hot with the fill plug removed, the final fluid level will be too low. If the fluid does not reach 40°C, the level may be overfull.

Also, ZF advises that before the fluid reaches the correct temperature, with the engine running, the gearshift lever should be moved to Reverse and Drive, pausing at least three seconds in each gear position to help ensure the valve body is full of fluid when the final fluid level is set.

Cheers,

Don

 

Yep, I just have to re-fit the sump heat shield this morning, now the exhaust will have cooled down, and she will finally be back on the road. The large rubber bung under the intake manifold has now been fully sealed with RTV so if that small coolant hose ever leaks again the coolant will spill out over the top of the bellhousing and it will be obvious where it is coming from. I doubt whether having the flex plate and torque converter sloshing around in engine coolant was ever a great idea!

The manual states that the fluid temp must be between 30°C and 50°C but it was so hot here yesterday that the fluid temp as read by my OBD scanner showed 29°C even before I started the engine. By the time I had run through the gears a couple of times, it was at 34°C so that's when I started filling. I only needed to add the extra litre of fluid as I had already added the full 7 litres which came with the kit whilst the box was still out of the car. It only took a minute to add one more litre so the temp was still below 40°C.

In the past, I have occasionally drained the fluid again after a couple of weeks to further dilute the old fluid left in the torque converter but this is obviously not a cheap procedure if you use the genuine LifeGuard fluid. However, on this occasion, I had only 1.5 litres of old fluid from the torque converter remaining in the system and 8 litres of new fluid so I definitely won't be draining it again this time. I have another ZF fluid change lined up, this time an 8 speed which will still be attached to the car, and I will definitely be dropping the rear wheels to get out that additional fluid. I'm a little surprised that I've never read about anyone else using this drain technique.

I've spent a lot more time on this job than I intended but a couple of unintended benefits were that I was able to cleanly snip the end off the duckbill with scissors and, whilst the prop shaft was out, I was able to change the diff oil seal which had been dripping oil for some time.

Richard

 

You should be good on the fluid level.

For the benefit of others who will read this thread in the future, all the ZF manuals state that the fluid check procedure begins at 30°C or 35°C, but that the optimum temperature for setting the fluid level is 40°C. If the temperature exceeds 50°C, the transmission must be allowed to cool and the procedure repeated. Here is one of the ZF/Jaguar documents:




If you are using SDD or a scan tool with Live Data, you can monitor the transmission fluid temperature via the temperature sensor. If you are using an infrared thermometer to monitor fluid temperature, aim the thermometer at the fluid emerging from the transmission and not the pan, since the plastic is a poor conductor of heat and the pan temperature can be several degrees lower than the actual fluid temperature, leading to underfilling of the gearbox.

Cheers,

Don