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1980 TR7 Brake Problem.

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Lagodude Avatar
Lagodude Garry Bayer
Lago Vista, Texas, USA   USA
Hey Peter,

No firm pedal.

Pedal bottoms out with some rear brake.

Thanks,

GarryB

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Lagodude Avatar
Lagodude Garry Bayer
Lago Vista, Texas, USA   USA
Vance,

I am going to check the vacuum hose and get a vacuum gauge and check it.

Thanks for the suggestion.

GarryB

carltr7 Avatar
carltr7 carl g
halifax, ns, Canada   CAN
Hey Garry
Ive been through everything you've been through.
I ended up frankensteining my brake system with various bits from other cars (see my pages) but leaving that aside I think my main observations when trying to get the brakes bled were:

a. it takes AGES and you go through a TON of fluid no matter what
b. getting a syringe and sucking fluid through seemed to help
c. bench-bleeding the MC and brake pressure splitter valve seemed to help
d. being anally retentive about every joint and MC level seemed to help
e. ignoring the manual at the back and going to a T in the middle feeding each rear cylinder at the bottom certainly helped.
f. new rotors and pads helped
g. having clear bleeder tubes and the jam jar above the caliper/cylinder I was bleeding helped.

You probably already know all of this but Im trying to be systematic.
Not sure if I can put my finger on one foolproof thing that I did.
I do now have a rock hard brake pedal, though.

For the record I run without a servo but with a Taurus SHO M/C, V6 Accord front calipers and OEM rear cylinders.
So it's certainly possible to have the brakes work well even minus the servo.
In my case the improvements were slow and incremental.


Good luck!

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Lagodude Avatar
Lagodude Garry Bayer
Lago Vista, Texas, USA   USA
HI Vance,

Sorry for my slow reply.

Yes, lots of money and time. Grasping straws.

I've followed your suggestions on testing servo (it's new, but) the servo works properly.

Purchased a Vacuum Test Gauge and tested vacuum from manifold, a steady 17 inch. No leaks.

Pedal has full travel, no restrictions.

I have purchased new DOT4 brake fluid and will continue to bleed.

Thanks for your help,

GarryB

Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1495307 by Lagodude HI Vance,

Sorry for my slow reply.

Yes, lots of money and time. Grasping straws.

I've followed your suggestions on testing servo (it's new, but) the servo works properly.

Purchased a Vacuum Test Gauge and tested vacuum from manifold, a steady 17 inch. No leaks.

Pedal has full travel, no restrictions.

I have purchased new DOT4 brake fluid and will continue to bleed.

Thanks for your help,

GarryB

Garry:

Wow. Everything sure SOUNDS like it ought to work.

I don't recall... did you replace the rear hose when you replaced the front hoses? I would imagine that you did, given your herculean efforts to get the whole system working.

You said you replaced the pressure reduction valve. How did you source it since it is NLA?

Time to think outside the box... I don't know about you but it really hurts when I try thinking... eye popping smiley

OK, how are you bleeding the system? Pumping the pedal? Perhaps vacuum bleeding would make a difference. ...or... some speed bleeders. They have one -way check valves in the nipple, so that air cannot sneak back in.

These are WAGs (Wild ass guesses) I admit. But you have gone through everything, and no joy. All that is left, I think, is something out of the ordinary.

BTW, vacuum bleeding really doesn't work with DOT5, since it foams rather badly (hence it cannot be used in anti-lock brakes). But since you mentioned DOT4, I think it is worth a try. I have found that this tends to pull air in around the bleed valve, so if your bleed valves are loose and sloppy, it does not work very well.

Some other questions - any evidence of corrosion on your brake lines? I suppose you might get a pinhole in one if it corroded, since the original brakes lines are steel tubing. But I would expect a leak of brake fluid somewhere if this were the case. Just a thought. It MIGHT be a one way leak, pulling in air but not really letting any fluid out. confused smiley

Another weird idea - What kind of flares on your brake lines does your new MC expect (I am assuming it is not an OEM style MC)? The original wanted bubble flares on the tubing perhaps you have the wrong flares (SAE vs bubble flares?) causing a leak? Once again I would expect to find brake fluid on the floor with this, but perhaps it just results in air being pulled into the system. Vacuum bleeding would show if there is a leak that admits air, as you would not be able to get a bubble free stream of brake fluid out of the system. If a bubble flare gets crushed or over compressed it will not seal.

Have you sufficiently tightened the fittings on your new brake hoses? The fittings will admit air if they are not tight.

These are all pretty wild, but perhaps they might inspire an epiphany on your part.

If you are inclined to look at any of these WAGs, I might try the speed bleeders to start, as that is the least outlandish idea of the lot.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

Rburgess Avatar
Rburgess Randy Burgess
Fresno, CA, USA   USA
I struggled to get my brakes working properly but my problem was much less severer. I did want to mention that early on I got rid of the stock proportioning valve in favor the part offered at the Wedgeshop. I’m not suggesting that this will fix your problem but if you are worried about your valve and have trouble finding a good one, this is a good option. Turned out that this had nothing to do with my problem but in the end, I think it helped my braking over stock and should I upgrade my brakes in the future, it is suppose to really help

http://www.thewedgeshopstore.com/50-50-proportioning-block/

sliproc Avatar
sliproc Kevin Quistberg E
Long Beach, california, USA   USA
Garry,

I don't know if this will help or add to your confusion, hopefully the former. Last year I did some hydraulic work on my TR-7 due to a collapsed front brake line(original). I ordered replacement parts for the brakes(MC, flex lines, etc.) while I was at it I decided to replace the clutch master and slave, the complete set being on sale at VB. The brake redo went fine, but after installing the new hydraulic clutch system I couldn't get enough pedal to engage the clutch, I bled 'til I bled. After much frustration(what you're going through now) I found the problem. There was a tiny pinhole fracture in the (new)hard plastic line between the two cylinders. I didn't find it initially because it was between the motor and firewall, it dribbled just enough to keep the clutch from fully engaging but not so much that fluid loss was noticeable.
The point is it was a new part and it failed and the failure was obscure. For some reason you're not getting proper pressure in the system, you've checked(or replaced)the obvious now maybe you should start to think about the possibility that your system may developed an inadvertent pressure relief valve.

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navydiver Rob Cornick
san diego, california, USA   USA
1975 Triumph TR7 "The Pumpkin"
1977 Triumph TR7
1978 Triumph TR8
1980 Triumph TR7 "The Plum"    & more
have you got the non return valve in the vacuum line and if so is it installed the correct way round? the lack of or malfunction of this will cause both symptoms you're describing (rough running and poor brakes).
cheers
Rob



1975 TR7 FHC Ca Spec ACL 4spd
1976 TR7 FHC Ca Spec 4 spd (Temp add)
1977 TR7 FHC ACW 5Spd
1978 TR8 DHC ACT FI development car 5 Spd
1980 TR7 DHC FI Spider 5spd
1980 TR7 DHC FI Spider 5Spd
1980 TR7 DHC FI 5spd
1980 TR7 DHC FI 5 spd
1981 TR7 DHC FI 5 spd

dursley Russ Cooper
Dursley, Gloucestershire, UK   GBR
If you have fitted a new dry master cylinder they can hold air and cause all kinds of problems. I have found I had to bleed mine separately BEFORE connecting it into the car system. Just made up a short pipe and returned the fluid to the reservoir and pumped the pedal until it ran clear of bubbles then connected the rest of the system as normal.

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carltr7 Avatar
carltr7 carl g
halifax, ns, Canada   CAN
In reply to # 1496183 by dursley If you have fitted a new dry master cylinder they can hold air and cause all kinds of problems. I have found I had to bleed mine separately BEFORE connecting it into the car system. Just made up a short pipe and returned the fluid to the reservoir and pumped the pedal until it ran clear of bubbles then connected the rest of the system as normal.


+1 for this.
Bench bleeding the MC helped me a lot!

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