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Dart rear caliper pistons ??

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hum966
Posts: 4
Joined: Tue Jan 31, 2017 1:03 pm
Location: Warrington, Cheshire, UK

Dart rear caliper pistons ??

Post by hum966 » Thu Mar 28, 2019 9:05 am

Hi in the process of releasing the rear calipers after 12 month+ period of standing in the garage.
Released the rear caliper pistons to find small amount of rust pitting starting on the chrome diameter, I have stainless pistons on the front and would prefer to replace the rear pistons with stainless.
After searching the web I have not found a specific component for the Dart, (I have yet to call Manners and B Thorne). Spoke with MEV spares who only has the hard chrome item.
I have found other stainless possibles ( need 43mm O/D by 29mm high) below. Has anyone tried them ??
I have an old note in my spares book with Dart Rear pistons = Jag 420, A60, girling part 64325436 also ?E type Ser 2?

http://www.jagspares.co.uk/Manners/Pricelists/E42.htm Part 11372SS
https://www.sngbarratt.com/uk/#!/Englis ... R%20BRAKES
Also Part 11372SS
Any thoughts welcome
Rgds Brian.

Sydsmith
Posts: 768
Joined: Sun Feb 14, 2016 11:15 pm
Location: Aberystwyth Wales

Re: Dart rear caliper pistons ??

Post by Sydsmith » Thu Mar 28, 2019 9:22 am

Barry Thorne is your friend for these, he normally has them in stock and is usually cheaper than David Manners. Syd

hum966
Posts: 4
Joined: Tue Jan 31, 2017 1:03 pm
Location: Warrington, Cheshire, UK

Re: Dart rear caliper pistons ??

Post by hum966 » Thu Mar 28, 2019 11:21 am

Thanks Syd I'll give Barry a try. Rgds Brian

tjt77
Posts: 479
Joined: Wed Mar 23, 2016 7:01 pm

Re: Dart rear caliper pistons ??

Post by tjt77 » Fri Mar 29, 2019 10:40 am

I believe the SP 250 originally came with Dunlop brakes..( actual calipers held to housing with 4 bolts each.. same as V8 2 1/2 litre saloon) and if so, some light corrosion on the actual pistons once cleaned up will not effect operation.. what WILL effect them is corrosion inside the bore of the actual cylinders.. if pitted in the bore, they will leak. (seal is fitted on the piston.. its seals against bore of cylinder)
The posted link above shows 420/series 2 E type rear brakes..these are different design (also fitted to V8 '250') which interchange as an 'assembly' and are a totally different design (made by Girling.. the seal fits in a groove in the bore..and seals against the piston). in these any pitting on piston will cause a leak.. light pitting in the bore effects little .

Sydsmith
Posts: 768
Joined: Sun Feb 14, 2016 11:15 pm
Location: Aberystwyth Wales

Re: Dart rear caliper pistons ??

Post by Sydsmith » Fri Mar 29, 2019 1:27 pm

Quite right, the original SP250 calipers are Dunlop and as far as I am aware, what Brian has asked for are available from Barry.

They may well match other pistons from other makes of caliper, but original calipers are not too easy to find so it is a good idea to fit stainless to prevent any damage to them.

At the risk of starting something I would drain the system and use synthetic brake fluid at the same time. Syd

tjt77
Posts: 479
Joined: Wed Mar 23, 2016 7:01 pm

Re: Dart rear caliper pistons ??

Post by tjt77 » Sat Mar 30, 2019 4:47 pm

On the subject of brake fluid :- does anyone use 'DOT 5' or silicone brake fluid ? Standard brake fluid is hydroscopic ( holds water)and if not changed at the recommended intervals (most simply dont bother ) will cause the problems we commonly find ..internal corrosion leading to lack of function.. almost a given if the car is parked for an extended period with old brake fluid in its system. It is also a highly effective paint remover..(silicon fluid is inert and does not damage paint)
there is LOT of negativity surrounding silicone brake fluid ..and it seem to be dissapearing from the shelves of most parts suppliers whilst Ive rebuilt systems that failed after using it.. Iv'e never experienced a single problem myself related to using silicon brake fluid in my own cars..

BUT..due to past experience with other peoples cars, Ive never used it in an old brake system, only in one that has been fully rebuilt with cleaned lines, new cylinders. flex hoses and/or seals.
My experience (admittedly, in a very user friendly climate ..no extremes) has been that it preserves the life of the system and results in virtually NO internal corrosion when cars are left sitting for months at a time.
what I have found when dismantling failed systems that used silicon fluid along with the usual nasty gunk, is soft and swollen seals ( similar to age related issues with standard fluid) and blocked flex hoses ( the most common problem next to corroded hard lines in old neglected braking and other hydraulic systems) Ive never experienced the 'soft pedal' that others have reported with silicon fluid.. I'd also note that the restorer I use for rebuilding dunlop brake cylinders ( they re-sleeve them in brass) has a warning notice with all their rebuilt cylinders :- 'the use of silicon fluid will render any warranties null and void'.. interested to hear the experience of others.

smithgor
Posts: 43
Joined: Sat Mar 25, 2017 9:13 pm
Location: West Yorkshire, UK

Re: Dart rear caliper pistons ??

Post by smithgor » Sat Mar 30, 2019 5:12 pm

Winter before last I fitted new seals and stainless pistons, supplied by BT, along with aeroequip stainless braided hoses front and rear.
Also filled with silicone brake fluid.
I've been very pleased with the resulting brake performance - non servoed. Pedal travel reduced, no perceived downsides from the silicone fluid.
I'd thoroughly recommend going this route, although I appreciate I'm only a year in.

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JohnM
Posts: 83
Joined: Thu Feb 11, 2016 1:31 pm
Location: N W London

Re: Dart rear caliper pistons ??

Post by JohnM » Sat Mar 30, 2019 11:43 pm

Now 9 years in on silicon fluid with a servo and no probs so far . Like Smithgor I fillled with Dot5 after a complete rebuild of the hydraulics - I've no experience of adding it to a system that's been run on Dot4 or Do5.1 then drained.
My personal experience is that silicon is prone to microbubbles, so after fillling the system it needs to be bled slowly and deliberately so it isn't "frothed" in the master cylinder, then left for a day or so for any microbubbles to coalesce before bleeding again to get a "hard" pedal that will then remain.
As an aside - the silicon saved my newly painted engine bay on first bleed of the system - a joint wasn't quite done up properly and sprayed fluid over the bulkhead!

I've also seen servo suppliers with the same disclaimer as TJT77 (the one for my Gilbern had it). No idea why, as the US military spec the fluid was developed for says for use in all vehicles........

John
John M in Middlesex, NW London
1962 SP250 "B" Spec

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