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V8 250 brakes

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Sydsmith
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Location: Aberystwyth Wales

V8 250 brakes

Post by Sydsmith »

I am reasonable switched on with these problems normally but my V8 250 is suffering an odd problem with the brakes.

Once in a blue moon the brake pedal drops to the floor, a quick couple of pumps and things are back to normal, brakes 100% and it might be months and many miles before it happens again usually within a few yards of starting off. It is complete brake failure nothing, their at all, I have checked the obvious many times with no fault found.

Today, out on a pre Drive it Day check out run, it happened again, I also have a problem with the front near side calliper binding, so its time to sort both problems.

The binding pads problem should be straight forward but I am unsure about the foot to the floor issue.

I am thinking a possible servo problem, or master cylinder seals, has anyone any experience of this or could shed some light on it.

classiclife
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Re: V8 250 brakes

Post by classiclife »

Hello Syd,

I believe your problem is master cylinder related; the fact the pedal drops to the floor means there is no hydraulic pressure occurring in the system when the pedal is depressed. The servo cannot assist when there is no hydraulics to act on. As you know, servos do not improve braking, it just makes braking easier with less pressure being applied to the pedal.

The fact hydraulics is restored on pumping the pedal, implies that the hydraulic pressure is being built up again to a useable situation.

It is likely, that this is a sign of internal seals starting to degrade which over a period of time will degrade further with the symptoms you describe becoming more regular. If the seals are failing it is also possible that there may be bore wear in the cylinder which is allowing fluid to get past.

As for the caliper, most likely a sticking piston or the sign of a collapsing hose; albeit I would say the former.

Hope that is a useful "starter-for-ten".

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

Sydsmith
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Posts: 1369
Joined: Sun Feb 14, 2016 11:15 pm
Location: Aberystwyth Wales

Re: V8 250 brakes

Post by Sydsmith »

Thanks for the input, that's is logical Richard, can't think why that escaped me, of course the servo cannot be the problem.

Had a look at it today and have decided long over due new seals and hoses all round and an overhaul or replacement of the master cylinder would be a wise thing.

I have had the car 9 years, the chap before me had it for 8 years, he did nothing himself and kept every little receipt for parts and garage bills. There are no receipts for brake seals, so they have done very well and are long overdue for replacement.

Might well change to silicone fluid at the same time.

Thanks again Richard for jogging my old grey matter. Syd

classiclife
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Re: V8 250 brakes

Post by classiclife »

With 17yrs already achieved by the MC, it is likely that there will be some bore / piston wear along with the weakening of the spring. The 3x seals within the MC will certainly be looking to elect early retirement by now !!

I'd certainly consider a replacement unit, but that's just my personal preference, Syd.

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

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