An interesting problem that leaves me slightly puzzled. None of this is rocket science, but a concern.



I was under the car to remove the undercover for cleaning and noticed some sort of oily substance on my tire and wheel on the driver’s side. Did not take long to see that the banjo bolt was leaking. So I got a new one and 2 new copper washers. That went on fine and no more leak. I had a friend help with the brake pedal to bleed that caliper. That took a short time and the brakes firmed up. The fluid was a touch above max, but only by a very small amount and so I buttoned every up and called it a day. The test drive, although short, did not show any issue.

I have had zero problems with any of the brakes and have used top quality pads and rotors from Pagid. I have about 70% left on the front and 80% left on the rears. No problem with the system and no noises. The calipers I replaced about 3 years ago and maybe have 12-15k on them (not very much). I have used quality fluid the last time they were bled some 3 years ago (super Dot 4 byPentosin).



Yesterday I started to notice a slight problem. The brake pedal has really firmed up and it does not take much to stop and if I come to a smooth stop- no problem. However if I sit on them or stop and push the brake pedal harder the driver’s side caliper is not releasing as quickly as it should until I start rolling and you hear that standard pad to the rotor slight “groan” as it releases. The brake rotors are not overheating and the rotor appears to move freely when driving. I could live with the noise and the very slight drag until I start to roll, but it should not me this way. It is almost as if there is too much pressure in the system.



Yesterday I took off the he wheel and removed the caliper and re-greased the sliding bolts, although they did not appear to be a problem. Cleaned around the caliper pistons but they seemed to have zero problem sliding back and forth. Cleaned the area with brake cleaner. The rotor and pads are fine. Put everything back together and still have the same problem. I noticed when I slightly depressed the pistons to slip the caliper back on and had moved them in and out smoothly that some of my fluid in the reservoir had gone near the top. So I removed enough to get down to max line. Does not make any difference that the fluid is hot or cold as it was this morning- still the same problem. I should mention that it brakes straight and does not pull to one side or the other.



Does anyone have any suggestions or solutions or explanations.



Thanks in advance!



Tom in Dallas/Plano 2005 S-type 3.0 118K

 

This could be a faulty flexi brake hose.
I have known these to fail internally creating a sort of non-return valve in the hose.

Mellow

 

I've experienced this. An easy way to check is to duplicate the fault, and then crack open the bleeder screw at the suspect caliper. If any fluid shoots out, you know something was holding pressure there. An internally collapsed brake hose would be a likely culprit.

 

Thanks for your response.

I had considered that. However there seems to be a cause and effect here. All I did was to replace the copper washers that on the banjo bolt and then did a quick bleed on that caliper and all seemed good. There is a however. When I got a pack of mixed cooper washers at the auto part's store in my haste I put on the correct washer size from the banjo to the caliper, but now I notice that the bottom washer from the bolt to the brake line/banjo is thicker than those on the other 3 wheels. The caliper seems to work back and forth fine, but seems slow on the return.

My logic might be telling me that that the extra thickness of the bottom washer is not placing the 2 outlets from the bolt to the brake line to be in the exact position they need to be so a minor restriction occurs on the release of fluid.

We will find out today and if that fails I will just get a new caliper and see what happens then. However the caliper pistons did not seem to have any difficulty moving back and forth when I checked the caliper.

Any thoughts?

Thanks

Tom

 

Thanks for the response. Check my response to MELLOW and see what you think.

Tom

 

This sounds very reasonable to me. Fluid enters the caliper under high pressure, but exits under very low pressure. A partial restriction would be more noticeable on the retract cycle. I have no problem with you getting messy to replace the washer and see what happens.

 

Thanks.

I assume washers are a certain size for a certain reason. When I looked up the part number in my EPC and found the dimensions were 2cm x 2cm x 0.001cm, I know for a fact that at least one washer is too large.

I will let you know.

Thanks

TBB

 

Actually did not get too messy. I called the dealership in Grapevine, ordered the 2 washers to be sent out on Monday and found out the part's guy, unknown to me when I had called, lived 3/4 of a mile from me and he had to pass by my home within about 100 yards and so while I was at the gym, he dropped them off at my home on Sat.

Put them on today and the problem is gone. So apparently it made enough of a restriction to cause the problem.

What can I say?
Thanks to all

TBB