Brake fluid for Triumph TR7

[busheytrader]

Hi,

When was the car last driven and when was the single rubber brake hose at the back changed?

Adam

TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes, Anti- Dive, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 5 Spokes and Cruise Lights. No Door Stickers. Mine since July 1986, V8 from 1991

[Underdog]

Agree with what Spyder said. Only time I had a problem with the 2 person method was when the GF was pumping the wrong pedal.[:0]

Had a RB MGB once that wouldn't bleed the rears. Turned out the master was junk. Similar unit as a TR7/8.

Jim Underwood
72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.

[Middle7]

In response to busheytrader, the car is driven daily, winter and summer. I don't know when the rear flexi was last replaced. I was thinking of going for a braided set at some point, so now might be a good time to splash out.

I have tested the brakes with the car jacked up at the rear and both sides bite well when the predal is depressed, and release immediately once the pedal is released. The car also passed the MOT recently without problems. If the rear flexi had colapsed would the rear brakes either not work at all or if they did would they not release fully due to fluid not being able to flow back to the master cylinder? Or perhaps the operating pressure is so much higher than that used in the bleeding process that the collapsed hose wouldn't show up during normal driving?

[Jolyon39]

I can understand the rear brakes working with foot pedal but not with vacuum.

On an old flexible hose I think that when you suck brake fluid through it the pipe would be drawn in by the vacuum effect. The converse applies when you push the brake pedal and force brake fluid into it the flexible hose would expand.

Lovely job replacing that hose. I suggest you get new nuts for the new hose as well. This allows you to grind off the old hose with rusted threads and nuts, the only way to go if it is aged with rust from salt etc..

Jolyon

[Hasbeen]

Middle, I am inclined to agree with you, about the brake hose. My experience is that it is the return of pressure where these hoses start to give problems, first.

Usually the first indication of a problem is that the brake starts to drag, & get hot, due to poor return of pressure. This is reasonable, as the pressure applied by the master cylinder is much higher, than that applied to the wheel cylinder, by the shoes return spring. This may still not work with vacume bleeding.

I have not had a problem with no fluid comming from the rear, but I have always found a 7 requires bleeding at least 2, & usually 3 times, over a couple of runs, & a few days, before a nice firm peddle is achieved.

This is strangely, still the case with my 8. Strangely, since the only bits of it't original brake system are the pipe & the reducing valve.

This car has Volvo booster, master cylinder & front callipers, with Nissan rear discs, & calipers. Although the brakes worked well, from the start, it still took 3 bleeds to get a fully firm peddle.

This tends to suggest that the blame for the any idiosyncrasies in the 7s system, can be aimed at the pressure reducing valve.

Can you get any fluid at the cylinders, by loosening the union nuts a couple of turns, at each cylinder?

Hasbeen

[Stuart Wilson]

What brake fluid are people using? DOT 3 or DOT 4 or DOT 5

Car has standard braking system but may be upgrading pad material.

[PeterTR7V8]

DOT 4 or 5.1 for competition. DOT 5 (different to 5.1!) is silicone based & the reaction with other DOTs which are glycol-based will damage the seals in a system that has any other DOT fluid present so unless you want to go crazy with a pipe cleaner don't use it.

[sst]

Dot 4 here..

[Stuart Wilson]

thanks for that, DOT 4 was the way I was thinking

[FI Spyder]

I use DOT 3. I know of people who have used DOT 5 for years with success. Only switch over if you've overhauled the the cylinders and calipers and flushed the lines. I thought of using DOT 5 after I did that but chickened out after hearing of difficulty some have had of bleeding. (I didn't have any problems.)

I would only use DOT 5 on the Spitfires as the master cylinder sits over a horizontal bulkhead just waiting to destroy the paint job when it leaks.

[Underdog]

Only problem I ever had bleeding it was when my GF was pumping the clutch instead of the brake.

Jim Underwood
72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.

[windy one]

LOL!!! I hear ya, had the same problem a few years ago :p

Johnny

[allzway]

I have bled many many brakes over the years and I think I know the answer to my problem. I am just looking for some validation.

I can't get any fluid to the brake calipers. I checked and had fluid at the master cylinder, the medal line before the rubber hose, but none after the rubber hose and none at the calipers.

I am assuming the rubber hoses have gone bad. I personally haven't ever seen a hose collapse that didn't allow some fluid pass, but it seems none is passing through the rubber hoses.

Do they go bad like I have described? Anyone seen this before? This car has sat for many years.

[dursleyman]

Not seen that personally but I have heard of it with really old hoses. If you suspect them then the only choice must be to replace with new. You could fit stainless and make a nice job of it.

[Hasbeen]

I have had a couple of instances where about 15 year old brake hoses were filled with a near solid "gunk", which pushed out like a worm, when a brazing rod was pushed through the hose. Those hoses were well cracked radially on the outside, & way beyond their use by date.

However they would allow the high pressure from the master cylinder to actuate the brake shoes on drum brake vehicles. What they wouldn't do was allow the full pressure to be returned to the master cylinder by the much less pressure applied by the shoe return springs.

Both were on drum brakes, & caused overheating with the drag of the partially applied brakes. One of these was on a long trip on little trafficked roads,
where I could drive up to 100 Kilometres between brake applications. After each use I would then crack the bleed nipple to ease the pressure. It was brake fluid that came out, so some must have been getting through.

Try running the engine to activate the booster, & see if the higher pressure will force something through. I suggest this only for interest, I would not use the hoses on the road. That I did once only shows how young & silly I must have been.

It is an interesting problem. Please let us know the answer.

Hasbeen