Overflow from brake res. filler cap

[Jaguar5993]

Hi,
On my 6.0 1995 XJS,I noticed excess brake fluid around the brake res. filler cap(about an egg cup and the level was at the top of filler point.)The engine was cold and had been in my garage overnight.

I have not over-filled it.

It has always been on the Max. mark and I renewed the fluid 18 months ago.
This is the first time this has happened in 15 years.
The brake performance is as always, good.
I syringed an inch out of res. level.
I started and ran the car, with the fluid stable and normal.

Is this a common problem due to age, or something else developing?(72000 miles).
Sort of thinking 'back pressure' from hydraulic accumulator/control module??
Could just a drain and refill, possibly stop this from happening again?
If there is fault present...it sounds expensive, although, as always,I would try a DIY job.
Any ideas welcome, thanks.

[Jaguar5993]

Hi again,
Just to let some of you know, that I have not gone mad or sleep-walked and filled my brake res. in the night!
I am still puzzled how this overflow happened.

Looking at it again today, I have realised that for the last 18 months (after I renewed all the rubber brake hoses),that I had filled the brake res.up over the Max. mark,but only by 6mm.
It hasn't had anymore fluid added since and it has not been parked on a steep hill.

Since noticing this last week, I have had no adverse brake problems.
Could a surge/blow back actually happen and cause the level to be pressurised out of the res, through the bleed hole?(not good to have a plume of air in the system, if the case?)

Its a mystery....
All is working normal and stable.
I will put it down to one of those things.
Keeps you on your toes, though!
Regards

[Tintin]

Hi Nick

Do you have the Teves system or the traditional servo system? I am no expert, but either way I have never heard of this before. If the system is properly filled and bled there is a fixed amount of fluid in a system of fixed capacity. If it was due to air present you would I'm sure have felt it in braking performance (or lack of it!). The only reason I can think of causing an overflow is that the system capacity reduced as when replacing worn pads or discs with new, or if for some reason the pads retracted beyond their normal "at rest" position (but I can't think why).

Unless any more experienced members have a view I would, as you say, adjust the level to correct and keep a very close eye on it.

Robbie

[Jaguar5993]

Hi Robbie,
My car is a 1995 one, but from MY Nov.1994,so no servo. I think from spring 1995 it was Teves (also rear vented discs).
I do have a possible rear piston problem, that I will get around to soon. I will definitely monitor it and report back.
I kind of thought it couldn't be air in the system problem....I was just clutching at straws.
Thanks for your reply
Regards

[Tintin]

The more traditional servo system came in to replace the earlier Teves system from model year 1995.25. So if your car was built in 1994 it must have the Teves system incorporating the nitrogen gas pressurised accumulator. The Teves set up is a specialist system and a bit of a dark art! Specialist troubleshooting required!!

Robbie

[Jaguar5993]

Thanks...Your dead right...I got it the wrong way round.
I have looked in the factory manual and agree,its beyond me(bit like the auto box as well).
I am hoping it will be fine?
All the best

[poprivet]

I'm not well up on the later cars, but if it's the same as the earlier Teeves, the reservoir has two sections with min and max levels at both front and back.

I guess it is possible that it was overfilled with the sphere pressurised (which would contain fluid). As the pressure was lost from standing a while, fluid would flow back into the reservoir causing it to overfill.

I would suggest you set the fluid level to max after ignition off, key out and pumping the brake pedal until the pedal goes hard.

[Jaguar5993]

Hi,
That could be the most logical reason so far,thanks.
I was really hoping it was a minor error on my part,versus major hassle and expense.
Its going to get very interesting with this sort of thing, in another 20 years, if I still have the car...(hopefully)?

[PaulGover]

According to my copy of the 1993 Appendix to the workshop manual (which runs up to the 1995 Appendix, and covers cars with the nitrogen-filled accumulator):

CHECKING THE FLUID LEVEL
Correct brake fluid level is essential for the efficient operation of the brake system.
There are two 'MAX' marks on the reservoir. The brake fluid level must be at the highest 'MAX' level on the reservoir (Fig. 1).
In some cases the fluid may be above the 'MAX' mark, this is dependent upon the charged state
of the hydraulic unit. Therefore the following procedure for checking or topping up the hydraulic
brake fluid level must be followed.
1. Ensure the vehicle is on a level surface
2.With the ignition switched 'OFF' pump the brake pedal at least 20 times, or until pedal travel becomes hard.
3. Switch the ignition 'ON'.
4. Wait for the pump to stop running.
5. Check brake fluid level. Fluid level must be be at the highest 'MAX level on the reservoir (Fig. 1).
Top up using the recommended brake fluid.
The efficiency of the brakes may be impaired if fluid is used which does not meet JAGUAR specifications.
Use ONLY Jaguar Brake and Clutch Fluid or Castrol Girling Universal to/or exceeding DOT4 specification.
Also do not use brake fluid that has been exposed to atmosphere for any length of time. Moisture absorbed from the atmosphere dilutes the fluid and impairs its efficiency.

This process will cause the level to increase if the car stands idle (say overnight) as the accumulator leaks fluid back, though not so much as to cause the reservoir to overflow. When you next turn the ignition on, the pump runs until the reservoir is recharged, at which point the fluid level should be back at or below 'MAX' depending on how much the pads and disks have worn since you last topped up the system.

[Jaguar5993]

Thanks Paul,good info.
I must read my manual more,rather than guessing.
My car had not been used for a week and the level being over the max mark,might of added to the problem.
Regards

[ptjs1]

Nick,

I'm still not sure which type of braking system you have. As mentioned the cars from 1995.25 Model Year use quite a different system, BUT 1995.25 MY started production from November 1994 at VIN 198335. So, if your car is after this VIN, you have the later servo ABS system

Paul

[Jaguar5993]

Hi Paul,
Ok here it is....My car was registered on 01.08.95(N),vin.195734.
It is the June 94> model(piped ruche leather,20 spoke wheels).
I think I saw some Nov 94 stamps on some engine components/pipes?
It def. does not have the 1995.25 vacume booster(vented rears).
So my car has the older 1993.25 ABS,with the hydraulic Accumulator,which might be the same for the MY 1992 5.3 facelift?
I am now confident that there is no fault with my system,just driver error..possibly?
Good learning exercise.
If I wasn't so tight,I would pay the £30 and get all my production details for my car,from the JDHT...
As always,thank you to all,for your interest and comments.
Kind regards.

[poprivet]

A happy conclusion to the problem, and knowledge gained by others who read these forums in both the technical aspects of brakes and the design build changes.

Thanks for the updates as things went along Nick.

[ptjs1]

Nick,

Your car is what is known as the 1994.75 Model Year. My estimate is that the car was built somewhere in about the 3rd week of June 1994, so I suspect unlikely that it would have Nov 94 stamps on any parts.

The braking system is quite complex on the car, so well worth a good read through that section of the Service Manual. Correct diagnosis of faults is quite critical rather than guessing at problems and changing parts (many of which are expensive or NLA!).

Enjoy the summer driving the car!

Paul

[Jaguar5993]

Paul,
That's brilliant information! It makes sense now.
Just had a look again at the label wrapped around one of the air-con pipes and it indicates 18.03.94(not Nov.94),so that fits in.
It's amazing that my car was built in June 94 and not registered until Aug 1995..
I know it's another topic,but I thought there was a final up-serge in XJS purchases in the mid 90's?
I am surprised mine was hanging about so long.
I wonder if the upcoming XK8,played a bigger part than I had thought, in shifting the last couple of years of XJS's?
After owning this car for 15 years,I still enjoy it and the sence of occasion.It turns more heads now,than when I first bought it in 2001.
Thanks again.