Low Brake Pedal

[teckwing]

I replaced the ABS module with a rebuilt one. Bled the brake system several times after several test drives. No warning lights or messages but I am getting a low soft brake pedal.

Any thoughts appreciated.
Tom

[mike020150]

The brake bleeding order for a standard XK8 is left front, right front, left rear, right rear. Whilst not normally a problem, bleeding in the wrong order could raise the possibility of trapping some air in the system which would be confirmed by a pedal which loses the softness when pumped rapidly in quick succession. Alternatively, two other possibilities are the use of silicon fluid which is slightly compressible and a faulty/incorrect ABS unit. Mike.

[teckwing]

Mike thanks. I did not know this and it appears to have been part of the problem. While working on it the check engine light came on and the red brake light. Since I am the third owner and suspect some shoddy work in the past I bite the bullet and took it to the dealer.
For the club members info this is what they found (for a price). They pulled the codes and found there are lean codes for both banks. They smoked the intake and found both the full load and part load breathers had been repaired with vacuum hose and were leaking. They also found the brake booster vacuum pipe was broken and had been repaired with a hose and it was leaking. These were replaced, although the vacuum pipe in on backorder so a temporary fix with a heat shrink hose was done.

Also I had installed a K&N air filter and this had wrecked the MAF sensor (so the technician said).

All this plus a new MAF and lose of my K&N added up, but we are on the road. Tom

[J44EAG]

Hello Tom,

I fail to understand the reasoning for the K&N being said to wreck the MAF sensor. Why?!

The K&N is just a high performance air filter which passes more air than a standard paper unit. That is all it does. It is unconnected to the MAF which only reads air temperature and mass.

I`d be most interested to hear the technicians explaination for making such a jockular statement. It is a non starter for me. Complete nonsense.

I find the statement quite illogical, in fact laughable and completely baffling! Still, I`ve had a good laugh about it. In my opinion, one of the daftest things I`ve heard in a long time.

I`ve run many EFI cars with K&N units and have never had a moments MAF trouble as a result. I`m loath to run any engine exept with such a filter on account of easier running characteristics, slightly improved economy and superior filtration.

Such units are not uncommon on light aircraft as the filter is unlikely to break up in service and be consumed by the engine perhaps causing an air emergency that could lead to loss of life. With a paper eliment, there is always a consumption risk, especially if the filter were to become damp. A K&N has a mesh support structure either side of the filter panel. A paper eliment does not. If there was a problem with a K&N type unit, then believe me when I say that the Civil Aviation Authority would have banned them years ago and I would not have been cleaning and servicing engines so fitted.

Go to Paramount Performance, Racing Green or any number of alternative tuning establishments and you will find they recommend a K&N type unit as the first stage of any tuning modification. Again if there was a problem, these guys would not be fitting them. By the same token nore would many other JEC Jaguar owners, many of whom (including myself) have run their cars using K&N or equivalent filters.

This is the first time I`ve heard such tosh. My suggestion would be to ignore the statement and put the K&N back in the filter box. Air filters do not wreck MAF sensors!

Rant over.

Kind regards,

Mike Kennedy. S-type Forum Co-ordinator.

[doug]

Hi

I have used a standard replacement K&N filter for years on a Classic Range Rover without problems and apparent positive result.

When I purchased my XK8 I intended to fit a K&N but read that there was a possibility that any excess oil (I assume only an issue if over oiled) could affect the breathing system parts of some cars.

Do you think this could be true or just someone jumping to the wrong conclusion?

Thanks

Doug

[J44EAG]

In my experience and opinion, one takes care not to over oil the filter at service intervals.

After cleaning, the correct K&N oil is aerosol sprayed onto the filter in just such a sufficient volume as to lightly colour the cleaned element a red/pink colour.

My article in the September 2009 magazine, page 37, details the proceedure.

I think the filter would have to be pretty heavily flooded to the point of saturation to have any effect upon component parts. The worst that could happen is to build excess oil up on the MAF sensor hot wires. As the oil is light desity, my view is that any excess would simply drip off under gravity onto the lower inside face of the induction pipe and be consumed by the engine as soon as it were started. As there is an induction depression (Partial vacuum) in the induction pipe, any oil/air mixture would be quickly burnt off by the combustion process when the engine runs. I consider it would be difficult for any oil mist to damage a MAF sensor.

MAF sensors do tend to accumulate crank case breather oil deposits over a period of time. This is the usual black sludge. Cleaning is easy with spray carburettor cleaner. The deposits just get washed away. Note that the hotwires should NOT be touched with tools.ie small screw drivers or other impliments for fear of damaging the hotwires. Spray cleaning is all that is necessary.

I wonder if Techwings sensor became damaged at some point and the blame then subsiquently became attached to the filter as the offending course. The MAF sensor wires are easily damaged if ham fisted techniques are applied.

Mike

[teckwing]

Mike and Doug

Great response and good information.
I also have used a K&N filter for many years in various cars without problems. So I must admit I was a bit off guard when told by the service advisor that the filter was responsible. I told the service advisor that the MAF could be cleaned with electrical contact cleaner but that apparently did not work out for his technician. It is also possible that the MAF had been previously damaged.

I do know that the K&N was new installed out of the box so maybe it had excess oil on it. Did not appear to and even so should not have been a problem.

I would like to inform the service advisor of our discussion and get his comment. They may also be a bit disgruntled (as they are the only game in town) that I and a local Jaguar collector replaced the ABS module ourselves.

I believe we will also replace the brake booster vacuum pipe when it comes in.

Thanks for you comments and expertise.
Tom