breaks again i give up

FI Spyder · Postby **FI Spyder** » 30 Mar 2011 16:42

I never had any problems with brakes. I overhauled calipers (piston seals), master cylinder, new vacuum hose to booster as a matter of course, new rear cylinders (a matter of time as they are still good to overhaul). I had flushed out hard lines with propanol and compressed air (lots of compressed air to make sure there was nothing left in lines.) Shoes and pads were like new. Cleaned mechanical bits in rear drums and lubed touching moving parts with brake grease. Replaced new rubber hoses with braided to see the difference (didn't notice much if any). Never had any problems bleeding brakes or their operations. The point is it dshould work if everything was done correctly. I think once the problem is found it will be something simple and overlooked. (Isn't it always).

I'm not much good at diagnosing from afar as I use my sense of hearing, touch and eyes when diagnosing the problem something you can't do from a computer screen. It's the same way when I fix computers. It's just me. But two heads there would definitely be an asset. Sometimes you get so involved in a problem you can't see the forrest for the trees.

Hard pedal, engine off. To the floor when engine on, would indicate the booster is working but that extra pressure on the brake fluid is causing it to expand to somewhere it can't get to with less unboosted pressure. Binding caliper pistons? Binding rear cylinder pistons? Expanding rubber hoses if they're not braided? (I got caught with the expanding new rubber/plastic clutch hose thing). Did you use brand name master cylinder seal kit? (I used TRW from British Parts Northwest.) Brand X may be less precisely made? Seals put on right way? (They usually only meant to go on one way so expanding pressure opens them up to create a tighter seal with pressure.)

TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

John Clancy · Postby **John Clancy** » 30 Mar 2011 16:52

One other thing to check, or two really, are the valve thingies from the inlet manifold to the servo. If the one at the servo end is sucking okay then that should mean the one at the inlet manifold is okay. Given the work you've done you probably already know how to pull the plastic white connector out of the servo.

But it does sound like fluid is bypassing the rubber in the master cylinder.

Quite a conundrum you've got there but rest assured when you get it sussed you'll be very very happy. All part of TR7 ownership. I bet the brakes are going to be top notch when you finally get it on the road. Keep up the good work and don't let it get you too down.

<center>[url="http://www.triumphtr7.com/documents/sales/codenamebullet.asp"]Buy the story of the Triumph TR7/8 on DVD here[/url]</center>

Beans · Postby **Beans** » 30 Mar 2011 17:49

Did you use the correct bleeding procedure?

<center>

1980 TR7 DHC (my first car, now restored and back on the road)
1981 TR7 FHC Sprint (better known as 't Kreng)
[url="http://www.tr7beans.blogspot.com/"]My Weblog[/url]</center>

rocky_679 · Postby **rocky_679** » 30 Mar 2011 20:11

sure did i 1st did it by the book remove the plastic switch under master cylinder then bled the front n/s bleed nipple then did o/s front then the rear i think as brain dead at mo [:)]

stephen j dark

PeterTR7V8 · Postby **PeterTR7V8** » 30 Mar 2011 20:37

Are you getting help with the bleeding or doing it single-handed? I've never had a good result with the one-man bleeder gear. Get a car savvy mate to help.

Otherwise, take it to a mechanic, preferrably a brake specialist. Yes, its great to be able to fix it yourself but if that doesn't work & you are losing your rag then the sensible thing to do is hand it over to an experienced spannerman.

Good luck & stop threatening to use the crusher. It's like telling your dog breeders group that your exporting to China.

The map: http://tinyurl.com/wedgemap . The blog: http://www.forum.triumphtr7.com/topic.asp?TOPIC_ID=8548

rocky_679 · Postby **rocky_679** » 30 Mar 2011 20:46

my dads the mechanic im the helper [:D] i threaten to use the crusher hoping tango (tr7) mite here me an start to work

stephen j dark

Beans · Postby **Beans** » 30 Mar 2011 20:54

I usually do the bleeding in two or three stages.
So I bleed as per the book and repeat this once or twice.

<center>

1980 TR7 DHC (my first car, now restored and back on the road)
1981 TR7 FHC Sprint (better known as 't Kreng)
[url="http://www.tr7beans.blogspot.com/"]My Weblog[/url]</center>

Stag76 · Postby **Stag76** » 30 Mar 2011 21:04

Do all the brakes operate (wheels lock up) when you have bled them? You could try bleeding them with the engine running...may highlight the problem.

TR7 Convertible
Sprint Motor
MegaSquirt EFI

rocky_679 · Postby **rocky_679** » 30 Mar 2011 21:11

when ive bled system without engine running all wheels lock up yet start her up an brakes r rubbish an yes il give it a go bleeding it while engine is running [:)]

stephen j dark

Chunk · Postby **Chunk** » 30 Mar 2011 21:27

Hello, Phil the Car Mechanic here.
Hard pedal, engine off usually means all the air is gone, the air giving you a soft pedal.
I had an MGB to look at a few years ago, long hard pedal which went to the floor when you started the engine. Turns out there are Two master cylinders available for the MGB, one being longer than the other by 25mm where it goes into/onto the servo. Which means there must be Two pushrods available, from brake pedal into sevro. Or Two servo's. Get the short items together and a long pedal will occur.
Whether this applys to TR7 i don't know, but it's all British Leyland stuff. A longer pushrod might cure your problem.

1979 TR7V8 FHC.
DJE 4.6 Block and Heads.
22 years of tinkering and tuning......So far!
Now available in red.

Hasbeen · Postby **Hasbeen** » 31 Mar 2011 01:39

Sounds to me a bit like the master cylinder fails to hold under the extra pressure of the booster.

Still some of the other suggestions sound reasonable.

I'd jack the car up, & see if the wheels are locked when the pedal is hard, with the engine off. If they are I'd really stamp on them [panic stop stamp] to see if they failed.

Should give some direction, particularly if they are not applied engine off.

Hasbeen

FI Spyder · Postby **FI Spyder** » 31 Mar 2011 01:43

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by rocky_679

sure did i 1st did it by the book remove the plastic switch under master cylinder then bled the front n/s bleed nipple then did o/s front then the rear i think as brain dead at mo [:)]
<hr height="1" noshade id="quote"></blockquote id="quote">

I've always done it in the reverse (for past 40 years). Furthest from the master cylinder first (for LH drive that's right rear, then left rear, then RH front, then LH Front). In the case of TR7 it would be rear, then RH front, then LH front). For UK it would be rear, LH front, RH front. While I have good success with my $5.95 one way bleed valve, you get the last few tiny bubbles with second person pressing brake then quick release of bleed nipple followed by the quick snick up tight. The shock of the quick release shoots out those last tiny bubbles.

I don't think it's a case of air in the system as there's a big difference between spungey brakes and pedal going to the floor.

TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

rocky_679 · Postby **rocky_679** » 31 Mar 2011 12:42

ok here goes re bled system have good breaks wen engine is off an wheels lock up start the engine pedal goes to the floor an does not hold the wheels however if i remove the pip to non return valve on servo the break pedal comes back up is it servo, master cylinder, or the non return valves ?????

stephen j dark

FI Spyder · Postby **FI Spyder** » 31 Mar 2011 15:24

The brake pedal pressure is applied through the booster as if there is one piece rod through it (so if there is no vacuum you can still activate the brakes). It should make no difference if there is a vacuum or not the pressure will be transfered through it's just a matter of force. The vacuum multiplies the force by 2.5 I believe I've read somewhere. It's higher in other cars.

The non return valve holds the vacuum in the booster if the engine shuts down so you still have power brakes in that event for a brake application or two.

Removing pipe from valve cuts out boost and you revert to previous low pressure (relative) on the master cylinder piston. I think it's the master cylinder that is not taking the greater pressure (when vacuum assist is applied) on the piston and fluid leaks past the seals. Is there a piston/bore clearance issue or did one or more of the seals get put on backwards or incorrect seals inadvertently used? That's my vote.

TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

rocky_679 · Postby **rocky_679** » 01 Apr 2011 12:59

oh well have splashed out on new master cylinder an replacing both the 1 way valves on servo n inlet manifold heres hoping fingers crossed[:(]

stephen j dark

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breaks again i give up

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