108 brake piston freeze

[kpb]

OK all, hope this isn't unduly redundant, but...

Have fished through all available threads here in the hopes of finding the magic elixer for my ills. Inner piston on RF caliper is absolutely immobile. Air pressure, pumping pedal with other piston clamped, extreme lubrication, gingerly prying, and, of course, liberal expletives, have failed to persuade the &^%$#@! to allow itself to be removed soas to install the rebuild kit on that side. Even took caliper apart to have a better go at removal, but alas...

Am I just SOL and time to get a rebuilt caliper?? Cannot quite tell on ********.com which I need but will figure it out. Also just found a fellow nearby who has a couple 108s in his yard, should I see if he'll sell me one? Is it feasible to grab a boneyard caliper and think it will be A-OK with my rebuild kit?

What's funny is that I only discovered this because of replacing the front pads. Brakes felt 100% but from the looks of it, this piston has not moved much in decades. BTW, the heatshields which are in the rebuild kit were not on either front caliper. Are they essential to prolonging the life of the rubber seals? The seals are still pliable even without shields in place.

Also, I followed one of psfred's older posts (which I cannot now find) and it was a perfect step-by-step on this project which I have never done before. One item of chronology, when putting the new seal on the piston, I had backed the piston all the way in until it bottomed as Peter suggested. However, this made it very difficult to seat the seal lip in the ridge on the piston so I blew it back out a bit, seated the lip, then bottomed the piston.

Sorry so wordy, all responses gratefully appreciated.

kpb

[psfred]

If you cannot get it out, it's very likely so corroded you need a new caliper anyway.

It is stuck pretty far out? Can't be, if you had new pads in there, though.

As a last resort (understanding that it's likely far too corroded to use), try tapping it sideways back and forth in the bore, alternating this with prying up with a pair of small prybars.

I would definitely look for a new caliper, though (used is fine, just do the rebuild on it).

Heat sheilds do just that -- sheild the rubber parts from the heat generated by hard stops. Makes the rubber last a lot longer.

Peter

[kpb]

Thanx Peter. Surprisingly, the piston was not frozen all the way out, it was locked about 1/2 of the way, so when I redid the pads last week and discovered the problem, I just inserted one of the old worn pads at that spot so I could drive in the interim. Hey, 3 new pads, one old equals 75% of a brake job, right? AND, the brakes felt fine!!

I will again try your tapping/prying idea but, have already knocked off a little smidge of the piston lip by such prying Guess I'm resigned to a few more hours/days of down time whilst I procure a useable caliper. Keep studying ********.com and the caliper which should be proper does not look just like mine because mine has allen bolts holding the two halves together and the photo shows nuts on bolts...

kpb

[j9fd3s]

i think i bought 2 new calipers for my 67 for $80 each, come to think of it maybe they were nice rebuilds, thats really not that much imo

[WANT '71 280SEL]

I got rebuilt calipers from autozone.com for 40-45 a piece for my mom's 420SEL. Then there's a 40-45 core charge of course. They were MB calipers and seem to be well re-built. It was so nice to see such old things looking so nice.
Thanks
David

[yeldogt]

If I was you I would look at both of them - this is one of those things that can really make adifference in the long run.

The cost of replacements is not that graet and if the rotors are in good shape with two new calipers and pads (also cheap) yo can forget the brakes for a long time.

I would bleed the brakes also.

The problem with old cars is sometimes you must do a little more otherwise you are back fixing the otherside in 6 months.

[Oreo]

Hi

I had a piston seize too that a piston retracting clamp would not budge. In end I levered it out using 2 flathead screwdrivers at 180 degrees apart on the groove of the piston outer seal with the fulcrum on the caliper body. There was actually very little corrosion and its still in use today with new seals.

You have to use 2 levers at 180 apart otherwise it will cock to one side and stick even more.

Oreo

[kpb]

yeldogt -- I agree, thanx for the input.

Oreo -- it was whilst trying this prying bit (with two screwdrivers across from each other) that I knocked a chunk of metal off of the piston lip so I did not persist. Maybe I'll try again today because my 108 is looking quite forlorn while I try to locate a caliper locally.

kpb

[kpb]

Hullo-- Tried Oreo's prying technique and pulled out a second chunk of metal from the lip of the piston Oh well. did locate a nearby boneyard (sort-of) and grabbed a 108 caliper. Took lots of cleaning and finagling with it to get it to act right, but, REJOICE, caliper is in place and appears to work!!

NOW, issue is, howinahell to replace rubber front brake hoses. Tried soaking them in PB Blaster - heat - pressure - cussing - what now??

Thanx all, you're collective lifesavers...

kpb

[Oreo]

Hi kpb

HAHA! Now its beome MY technique? I thought you did it on your own too? Anyway, you were going to write it off so nothing to loose. That must have been a lot of force you were using to break the piston metal. I guess its welded in there.

Better be patient soaking that brake hose, you don't want to break that threaded portion.

Oreo

[300SDog]

Gotta get longer handle to add leverage. Get yerself a 2 foot iron pipe that fits over most of your box/open-end spanners. The same iron pipe can fit over vice-grip handle if the collars get stripped. But if you can keep the collars intact, it's a piece of cake for the hose shop to just replace the rubbers.

---

Last edited by 300SDog; 07-28-2004 at 11:25 PM.

[kpb]

Oreo, you caught that implication, didya??

Dog, thanx for the ideas and caveats. Think I'll let the brake lines sit for the moment while I replace the fuel hoses on the fuel ring and the injector seals as well. Then I can start it and see if the brakes actually work

kpb

[300SDog]

Here's a good story for the forum about how much braking power most cars actually need.....

Donald Healey designed the Austin Healey 3000, easily the best rag-top roadster of the early/mid 1960's - first designed in 1953, i think.

When some kinda girlie-man news reporter whined about the car not having discs on the front instead of huge 13" drums on all four wheels back in 1965 or '66, Don Healey became annoyed and replied: "Good brakes discourage good driving habbits."

Crybaby reporters went berserk with this remark!! And all of a sudden crybabies all over the place started questioning the safety of the Austin Healey 3 litre sports car.

Some automobile historians believe this remark ended Healey's career..... a controversial yet brilliant engineer was Donald Healey, yet apparently he was also tough to get along with.

But Healey was right!! Anybody who relies on panic stops to slow down cant be much of driver at all.

At the race track, manuevering curves on country roads or even city streets - the same rule applies...... you shouldnt have to be slamming on the brakes!!

[kpb]

Dog, nice story.

[psfred]

True, perhaps, but when a child comes zipping down a blind driveway out into the road in front of you.....

Good drum brakes work just fine, but they are ALWAYS fade under heavy use, there is no way to prevent the drum "belling" out of shape with the open end larger. This is why aircraft have had disk brakes since the 1930s.

Peter