the flyin' scotsman

Now I'm real pissed.

I had thought the reason why I had little heat in the rear rotors was because of the regulator so I changed to the 33 reg. valve.

wow..........does the car now squat equally when hard on the binders but my LH rear is barely getting warm. All other rotors are ~50C.

Pads, caliper?

AO

Try bleeding, but if that doesn't do it, then I think it's proabbly caliper. You can try rebuildin, but it's probably cheaper in the long run to just get a used one.

Lizard928

I think what you should test first is how much pressure is getting to each caliper using a tool such as


http://www.wilwood.com/Products/006-...4-PG/index.asp

Also inspect the pads to make sure they are wearing evenly, side to side. Should be obvious if a caliper isnt clamping.

Yoakim Larson

You should always rebuild in pairs, however it may be a brake line, if the lines are old change them, good maintaince anyway, if this doesn't improve a caliper rebuild kit for both sides should only be $100. Good opportunity to give them a paint too.

the flyin' scotsman

The full scoop is new PBR Ceramic pads up front, new Goodridge brakes lines, new super blue brake fluid and new 33 bar regulator.

The rear calipers are, as far as I know, original and the only time I had them off was when I R&R the suspension. The pads, both sides, have hardly worn in 60k kms.

I'm thinkin' new calipers, rotors and pads.

JHowell37

I'm thinking you should figure out what the problem is before throwing money at it. I just put S4 calipers on my '85 a few weeks ago and it took three attempts before I got it bled properly. You just changed your proportioning valve which means a thorough bleeding is required. Why not exhaust that option before pouring in money?

the flyin' scotsman

Should have mentioned that the valve was changed at the same time the lines were swapped out and all 9 bleed points were bled with Super Blue.

PorKen

Malcom,

Do you have the part number for the 33, handy?

the flyin' scotsman

sure Ken:

928 355 305 02

Mrmerlin

you might want to trace the hard line to the rear caliper, there might be a chance it has been smashed flat, the other place to look is the T fitting take this apart and see if its clean inside.
The T fitting should be somewhere near the rear axles also check the hard tubing to the master that runs along the bottom of the car, If all of this checks good then I would do a pressure test to see what kinds of pressures are being generated to the rear wheels.
Check the pressures to the front wheels and also check the rear pads for binding in the calipers since they have not been worn in a while its possible the caliper may have corroded the pads in place. If you find nothing then a caliper rebuild might fix this problem, rebuild both since if one is doo doo the other side wont be far behind

the flyin' scotsman

thx MrMerlin................didn't realise that rebuild kits are available for the rear calipers, would you have a part #?

Mrmerlin

check with Jim Bailey at 928 INT, some changes for differnt vins if i remember correctly, he will know

BrianG

I thought the S4 rear calipers were NOT rebuildable....
I couldn't find a kit listed....

Garth S

Firstly, super blue or super-duper sky blue pink will give undectably different braking in a street car that achieved from a fresh, dry bottle of Canadian Tire/ NAPA/etc. cheapo DOT 3. Fluid choice is a fashionable red herring - OK, blue herring in this case.

If the good thinking above proves that the caliper in question is getting both adequate pressure .... and FLOW**, then check the pads and rotor for glazing: the caliper may provide the correct clamping force, but will not generate the retardation if glazed ( braking = friction = heat .... of which you have too little).

** the pressure test is a good idea - but only tells half the story: the correct pressure will be achieved even if the line is only open by the diameter of a pinhole .... it is after all, a hydraulic system, non-compressible fluid and all that neat stuff. The lines must be unrestricted ( bends/cripms/etc) to allow equivalent flow side to side.

the flyin' scotsman

Valid points Garth.

The LR caliper is working to a degree...........it erases a test mark on the rotor and does get to ~25c indicating that one or all the pistons are moving. No weird scoring on the rotor and as mentioned the pads have been in their since my ownership. The RR rotor is almost the same temp as the fronts ~45C.

..........and for a good de-glaze you recommend? Shiraz, Pinot Noir or a strong Cab.

Today 'maybe' the hang up the keys for the season............then we'll really get into to it.