Wilwood Calipers and uprated rear brakes

[Curtis Bay]

I have a 1965 Series one FHC (4.2) which has had the front calipers upgraded with Wilwood Dynapro 4 pot units from Classic Jaguar. In addition I have had new, larger (front caliper) pistons fitted to the rear calipers to maintain a similar balance between the front and rear brakes.

The problem I have is that the we cannot get both the front and back brakes to fully pressurise. We are certain there is no air in the system and have tried two new master cylinders and three new servo / slave cylinders.

Had I not seen several posts on this forum (and other information on the general internet that implies this is a 'standard' upgrade) I would be concerned that my slave cylinder on the servo cannot deliver enough fluid to the larger brakes and is bottoming out before full pressure is reached.

Before I return to standard size rear pistons has anyone got any advice or experience of this problem?

[1954Etype]

I have this setup and have no problem. Have you tried bleeding with an easibleed or similar?

[Curtis Bay]

Hello Angus

Can you confirm that you have Wilwood Dynapro calipers on the front because the size of the front pistons would appear critical.

Also, do you have the brakes plumbed in with the front brakes served by the front outlet in the slave cylinder (one furthest from servo) like the early 4.2's or does the rear outlet (nearest the servo) supply fluid to the front brakes like the later 4.2's.

[oldak]

I have wilwood front brakes and resleeved rear brakes and couldn't get any fluid out the back. When I pulled the rear cage to fix the rear brakes I noticed that after 30 years my rotors were in perfect condition, also known as no rear brakes for 30 years. I sent the master to be resleeved and rebuilt, it came back and still no fluid to the rear brakes. Sent it back for another rebuild and it came back with the same problem. They sent me back another one off the shelf and it worked. The original was not the original but a replacement that had some kind of factory defect that wasn't fixable with a kit.

To test the master cylinder remove the line to the rear at the master and put your finger over the outlet as someone pumps the brake. The bad master cylinder pushed fluid but then sucked it back in without ever moving additional fluid to the rear brakes. The good one pushed fluid and then pushed out more.

[Curtis Bay]

Thanks for the suggestion and believe it or not we tried three 'new' and two 'reconditioned' master cylinders when trying to diagnose the problem.

Eventaully I found out (by looking at photos of the rebuild process) that the crossover brake lines between the pistons on each of the rear calipers were installed incorrectly. The brake lines must enter the inboard piston at the bottom and then the crossover pipes must flow from the top of the inboard piston to the bottom of the outboard piston or a natural air lock will exist. When these were corrected we could bleed the brakes properly and I now have full brakes.

[e_fourtwo]

By the way; I have mounted the bigger and stronger later Servo (series II or III). Fits perfectly and pushes even stronger. Same setup from classicjaguar with Willwood in front and the ex-front calipers in the back fitted with drilled and slotted discs...

best regards,
Thomas

[Francis]

Angus,

Wilwood brakes kits does improve braking distances. However they can't be used with original rotors.
I kept the rear disc system and just did a full renew job on the calipers and changes discs. I also changed the fluid lines and reworked the lever mechanism. The read discs cable was also replaced.

While installing the Wilwood kit up front, I was confronted with a puzzling issue. It took me 2 days to figure out.

Every time I build pressure up in the braking system, it would not stay up very long. I had to pump the pedal once before getting real pressure.
It turned out that one of the caliper seals was ripped from the inside! Nothing that could be seen with the naked eye until you removed the rubber seal.

A brand new part that came with a 5 pence defective seal! Two days of frustrating work to find that one.

Willwood would not supply me with a new one... I had to go to a brake shop to get this seal measured up and matched with one available on the open market.

Once replaced, I got full pressure and real braking power.

I always say, a small Peugeot 103 has better braking power than an E-type. So if one brakes in front of you, you better have a 4 pots braking system up front if you don't want to end up with more damage on your bonnet then the whole value of the Peugeot!

Francis