The Triumph Dolomite Club - Discussion Forum

Since I've had the Sprint I've never been that happy with the feel of the brakes, over the past 3 years I have been slowly fixing/updating/fiddling with bits but its air in the braking system that's driving me bonkers!!

Its a single line early 79 Sprint, I have done the TJ upgrade and has no "load sensing valve" as it was thrown in box when I got the car, I have replaced all the pipe work to the rear, and the rear cylinders look ok.



Rear pipe work is slightly different as suggested by Steve B (Carledo)


I've inspected all the unions and can't see any weeping or feel any moisture, the level in the master cylinder never seems to reduce, but after the car has been standing for a while the peddle feels spongy and has to my mind far to much travel, so I bleed the brakes again!, at this point I must mention when I bleed the front callipers I never see any air coming out so they seem fine, but the back is a different story, first few pumps seem ok, then I get masses of air bubbles for about 8 pumps then it seems ok, but I reckon if I keep going I would see another bout of air coming through.

So how is the air getting in? I would expect a leak somewhere but I can't see anything.
My thoughts have turned to the Master cylinder, I have never touched it..but its old, should I suspect that? When pumping am I pushing air into the system from the master cylinder and it takes a few pumps to get to the back?



Any thoughts?

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Steve M

68 Triumph Vitesse convertible
79 Dolly Sprint

Did you change the rear flexi pipe, might be porous. If you haven't use a Goodridge stainless one.

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1979 Dolomite SE (Black Obviously)
2000 Saab 'Viggen' Convertible in 'Lightening Blue'

Dave

Yep, I changed that a while ago

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Steve M

68 Triumph Vitesse convertible
79 Dolly Sprint

What rear brake cylinders are you using ?

Apparently, smaller bore master cylinders balance the front / rear brakes.

I’m sure somebody will confirm the recommended size. I believe it’s not the Sprint part !

Thanks, Richard

I'd be inclined to suspect the master cylinder too.


But go round once more and check every union and fitting aft of the 4 way on the bulkhead, just to be extra certain. But if you are bleeding a single circuit system correctly, ie rear first, then you may be getting all the air out the back, hence none from the front!

The wheel cylinders to use are the 5/8" bore variety (GWC1502) from the Dolomite 1500HL. These will help with a low pedal associated with the TJ conversion (though for some reason it doesn't affect ALL TJ converted cars) caused by using bigger bore calipers.

But if you are losing pressure and getting air into the system and no loss of fluid, the usual and main suspect is the master cylinder.

The club can supply a stainless sleeved single circuit master cylinder if you need one, though personally, i'd use the opportunity to convert to dual circuit for extra safety. The price differential isn't huge, though you will need a few extra pipes and fittings.

HTH, Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 50 years. PM for more info or quotes.

I'm not sure what wheel Cylinders are fitted, I always assumed they where the correct Sprint ones as I didn't fit them, so I will definitely be looking into changing them to 5/8" bore variety (GWC1502)

The upgrade to the a dual circuit has got me very interested, but looking at the club spares options it states that its an exchange item and obviously I don't have one so that might scupper that.
reading back on old forum posts I wouldn't be fitting the PDWA just making up the new pipes and acquiring the 3 way adaptor, it also seems that you can supply this Steve?

So I'm going to have a think about which way to go, but my initial thoughts about the master cylinder being the culprit to my air in the system issue seems valid at the moment

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Steve M

68 Triumph Vitesse convertible
79 Dolly Sprint

5/8th bore cylinders are hard to come by. There are a lot advertised on eBay etc but they are actually 3/4 bore which I found out when I rebuilt my brakes. I eventually got OE Girling ones from David Kingerly 07977 914088 / 01332 873685

My car had one 11/16" and one 3/4" fitted before I replaced them. I also used Carledos PWDA bypass kit and fitted a SAAB 9-3 (pre 2003 brake fluid level sender) and wired that to the existing brake warning light as documented here on the forum.

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1979 Dolomite SE (Black Obviously)
2000 Saab 'Viggen' Convertible in 'Lightening Blue'

Dave

Just looking at the Wheel cylinder options and I think I might need confirmation
Robsport has the "GWC1121" as the 5/8" bore and in the PM it shows that as the Sprint version, "GWC1502" 1500 and 1850

https://robsport.co.uk/online-shop/shop ... 126-brakes

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Steve M

68 Triumph Vitesse convertible
79 Dolly Sprint

The Parts list has GWC1121 listed as for all Sprints, regardless of year or circuit config (which SHOULD make it the 3/4" one) and all 1500s and 1850s as well, after a certain chassis number (1850, WF68200) GWC 1502 is for all 1500 and 1850 models PRIOR to WF68200 so should be the 5/8" one. I know an 11/16" cylinder EXISTS cos i've seen a couple, but have so far been unable to trace exactly what the factory fit for it was, or it's BL part number.

Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 50 years. PM for more info or quotes.

You have a PM!


Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 50 years. PM for more info or quotes.

It's a Ford fitting Steve at 11/16"

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1979 Dolomite SE (Black Obviously)
2000 Saab 'Viggen' Convertible in 'Lightening Blue'

Dave

So I had a trip the NEC Restoration show yesterday and wandered along to our stand where lucky for me Alun (xvivalve) was doing his thing
He had read my post and knew that I was possibly looking to change the master Cylinder to dual.

Alun had a Dual Master on the stand, plus the pipe work and PDWA, I now have them and will attempt to make up my own pipe work.
I also got the end fittings from the Automec stand, If my attempts fail then I will then revert back to getting a set from Carledo

Having the PDWA I will take it apart clean and see if it will do the job, I'm not 100% sure I will use it yet but I do want to investigate the possibility
As for the rear wheel cylinders that's still a mystery, but I am going to measure the piston diameter (suggestion from Tony (Mig Wielder))

Of course it might still be the air is getting somewhere other than the Master Cylinder but I have to start somewhere, so why not start on a tricky bit and work back not my normal way of fault finding but it feels like an interesting task

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Steve M

68 Triumph Vitesse convertible
79 Dolly Sprint