Hi,
I usually post on the X308 forum, but my father bought himself an XJ40 Sovereign 3.6. It's a 1988 with the self-levelling rear suspension, and it appears the accumulator is broken.

The original accumulators (JLM11659) are getting a bit hard to find. As I understand it, there's alternatives available, since it's more or less just a standard bulb, but what are the alternatives actually?

 

Do yourself a favor and ditch that system. Loop the hose and install conventional springs and shocks. That's how Jaguar Cars fixed it. Hydronumatic suspension was was all the rage in 1988. BMW had it too on their 7 series and they punted on it too. If you want to fix it, you've been warned, a standard GM accumulator their hydroboost style brakes has been known to work. An application is 1987 Buick grand national p/n 18038507.

 

Unfortunately 'ditching' that system is NOT an option on the 1988/89 3.6 as the BRAKE system uses the hydraulics for BOOST.

You can retrofit the non-leveling dampers and a vacuum brake booster system from a different car to eliminate the system hydraulics.

You can also fit the 1990-1994 electric/hydraulic system but I would discourage that.

The hydraulic accumulator (GREEN) for the 3.6 was only used for those 2 years.

The GM accumulator (BLACK) is for the 1990-1994 XJ40.

bob gauff

 

Ok, thanks for the replies.

I had a spare 'brake bomb' for a BMW lying about and it could have fit (bigger capacity but lower pressure) - _except_ you can't get an adapter for the thread. The ATE accumulator from the BMW is threaded on with M18x1.5, while the Girling valve block on the Jag uses M16x1.5. We went to three different hydraulic supply shops and got nothing but shaking of heads...

But never mind, there's a local guy who has a used XJ40 accumulator, so it looks like it'll end well.

 

The way to test the accumulator when fitting second hand is to poke a small blunt screwdriver into the hole at threaded end. If it goes all the way in it means the rubber diaphragm inside has collapsed' if it just goes in a little bit it is normanly ok be cearfull not to puncture it. if the original one is ok the problem might be one of the valves attatched to the accumulator one is high pressure and the other is low pressure.They also give the same simptoms of brake failiure
Cheers Ray

 

Ok, so the used accumulator turned out to be a dead end (the guy couldn't find it). But there's a guy who sells replacements on eBay Australia, and dad gave in and ordered one. He got the package today, we assembled it, and now it seems to be working as it should. No more low brake pressure, and you get a huge amount of pumps before the pedal goes hard after shutdown.

If all goes well the car will be deemed roadworthy tomorrow.

 

Hello everyone,

This seems to be quite a common problem with many of the 1988/1989 XJ40 hydraulic accumulator setups? I have an '89 Daimler and have the extremely annoying issue of "Low Brake Pressure" appearing on my dash after a cold start in the morning.

I have a feeling the "brake bomb" you are referring too is the Nitrogen orb? But you are right in your method of testing them. However if your removing it from your car to test it make sure you 'exhaust' the brakes first - with the engine off!. A reasonably good orb should give your 30 - 40 pumps of the brake pedal before it should give you a firm pedal.

My car had the self leveling suspension removed long ago, but I'm now working through the annoying issues of the hydraulic system. so far:
-every seal has leaked and been replaced, hoses replaces for good measure (LBP warning still on.)
-Nitrogen orb. replaced. (LBP warning off Yay...... two days later LBP warning on)
-Now suspect low pressure switch is faulty. warning only activates when car is first started in the morning or stopped in rush hour traffic. If you have this problem here are the part numbers for the switches
High pressure: 74661549
Low pressure: 74661548

Those numbers apply to the switches fitted to the accumulators fitted to the 1988/1989 3.6L XJ40's only. I'm not sure if the 2.9's had the same system. The newer ones were totally different again.

Anywho. Good luck to your dad with his new car Roy!!

Cheers all,

Alex.