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Spitfire Bleeding Herald Brakes [similar to Spit]

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dklawson

dklawson

Yoda
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My friend Jamie has had his wife's Herald stuck in their workshop since his well intentioned son-in-law mistakenly added DOT-3 brake fluid to the master cylinder reservoir (6+ months ago). I am working with him this week to get the car mobile so he can use his shop again.

All the brakes are new (new shoes, pads, calipers, wheel cylinders, master cylinder, metal braided hoses).


He decided to convert to DOT-5 fluid. We have tried every bleeding method I know of and we still cannot get a firm pedal. We have used gravity bleeding, pump-release bleeding, vacuum bleeding, and the pump-pump-pump-crack the bleeder methods. (We do not have an Ez-blead so please don't suggest that unless it's the only thing you have had success with). The pedal remains mushy in spite of our efforts and about 2 quarts of DOT-5 through the system.


I know on BMC cars that the position of the friction material on the shoe can make a big difference on pedal firmness but I have not heard of that on Triumphs. Regardless, we'll check that tomorrow.


Do any of you have suggestions on how to bleed the brakes better to get a firm pedal? These brakes are basically the same as those on the early Spit (single line system with drum rears and disks front)... but with different hose lengths.


Thanks for your advice.
 
For sure adjust the shoes before the next bleed.
Just replaced a line on my TR4 and flushed the system with all new fluid. Used a vacuum bleeder with zero success, pump and release method with wife operating the pedal and me on the bleed nipples had a rock hard pedal in one trip around the car. I typically use a pressure bleeder that pushes fluid through the master and out to the wheels, but the adaptor wouldn't fit on the TR4 master.

With the amount of new components in the car, there are a TON of places for air bubbles to hide. A small hammer is my best friend when installing a new master or caliper on a car at work. Rap all the new components to dislodge any stubborn bubbles, then do the pump and release method. May take a trip or 2 around the car, but unless there's a mechanical fault with one of the new components it will work.
 
You must purge every last drop of 3 out of the system to go to DOT 5. Not compatible with anything. Not made for street daily driving. All new is a plus, bleed til it is hard.
 
LarryK said:
Y... DOT 5. Not compatible with anything. Not made for street daily driving.
Click to expand...

The following will be my only comment on DOT-5. I do not wish this thread to become an argument/discussion about the merits of the various types of brake fluids.
Both my friend and I have worked with DOT-5 before and there is nothing wrong with it when put in a clean, dry system, with new rubber bits, and without DOT-4/-3 in the system. That is the case with this car. DOT-5 IS for street driving. I cannot think of any racing body that allows it.

We have adjusted the drums right up to minimize pedal travel. It did not help much.

There are several things I will suggest we try tomorrow.
Bench bleed the master.
Force the caliper pistons all the way back in before bleeding.
Force the wheel cylinder pistons all the way back during bleeding.

If those don't work I will also suggest pushing the brake pedal down and holding it down over night. That is a trick I have never had to use but some people endorse for allowing trapped air to flow back up the lines and "out". (I don't see how that would work but we've got to try something).

Please keep your suggestions coming.
 
I won't argue. We used DOT 5 in all our restored show cars. Never a regular street car. It is a picky solution as everything needs to be completely clean of everything. Can be a bear to bleed (as you know). Try the wrench tap method on calipers and such, does help get air out. I use DOT 4 in everything because I track a lot.
 
Do I know this "Jamie"? I'm thinking I do.... :laugh:

Can you get enough of a pedal to determine how well the new calipers and wheel cylinders are functioning? Other than the 7" difference in wheelbase, there's really nothing that would be any different than a Spitfire and therefore might require some peculiar treatment or procedure! Oh, and are the new parts OE or aftermarket? Not sure if that might make any difference, but....
 
I put DOT 5 in my TR3 simply because I tend to spill everything and 5 is much easier on the paint. I don't think I'd do it again. I had a devil of a time bleeding it. I finally got an acceptable, to me at least, spongy pedal. The car stopped pretty much as it should in spite of the long pedal travel. After time the sponginess went away. The clutch, with DOT5 also, bled itself but the master plunger was and still is, slow to return. Of course I have no way to tell if it was the DOT 5 that caused either issue.
Tom
 
Last winter I replaced the entire brake system on my 1965 Tr4a. I decided to use silicone fluid. Using the 2 person method, I was able to bleed the brakes with no issues. When done, the pedal did feel a bit softer, but this may have been partially due to the new pads/shoes seating in. After driving all summer, the brakes now feel normal to me, so either they returned to the old feel, or I got used to the new feel!
Oh, and I also changed the clutch MC and SC, and used silicone fluid there as well.
One tip I was told regarding silicone fluid is that is it more susceptible to small suspended air bubbles than glycol based fluid. So it’s a good idea to let new bottles of silicone fluid to sit on the shelf a few days before use, to allow any suspended air from handling/shipping to release. Also when adding the fluid, pour slowly so as not to introduce air. Here’s a good article on silicone fluid:

https://etype.chrisvine.com/wp-content/uploads/documents/DOT5 Silicone Brake Fluid.pdf

Jim
 
If you can se if you can borrow a pressure bleed system.
The owner of the import shop, cut his teeth on LBCs, uses it whenever he has an issue with bleeding.
However, in the field he uses the 8 pump method, open a corner and give 8 slow pumps and then close. Go around the car. This usually works.
 
Hi Andy. Yes, this is the Jamie you know. This is the blue Herald that he has converted to dual HS2 carbs.

We worked on the brakes again today and they are much better. I bench bled the master, we filed chamfers on the leading edges of the shoe friction material, pushed all the caliper pistons all the way back, readjusted the shoes, and then re-bled the system with the 2-person "flush" method.

I suspect that the air left in the system yesterday was as Jim said above due to small bubbles in the fluid. Some may also have been trapped in the MC.

Regardless, my friend says that while the brakes are not perfect they are better than they were in the past and much better than they were yesterday. Now he can move on to all the other problems this car has.
 
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