404 brake saga

Gilow said:
One forum (on old holdens) mentions problems with a "minimum pressure valve" in the master cylinder causing problems with the VH40 booster. Could it be there is something like this in the 404 master cylinder?
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AFAIK the disk brake 404 master doesn't have a residual pressure valve.

If the braking system has been working properly at an earlier time then I'd think you are looking at something which has failed due to wear or age.

The master and/or hoses fit that hunch. Check if booster has fluid in it too.
 
No, residual pressure valve in disc brake 404 is in the 4 way junction as mentioned above.
 
I had a 1970 404 with the problem of the rear drums locking under heavier-than-usual braking, and the back wanting to overtake the front.

It turned out that the proportioning valve had the lines connected in the wrong position, which I think gave it some kind of bias.

Can't remember all the details, it was 40 years ago.
 
OK, some good ideas so far...

Looking at things as they stand.

1. The original VH44 booster gave adequate boost, but I have been suspicious of it for some time, hence I was happy to swap it out.
2. The swap to the reco VH40 seems to have introduced a lot of problems, perhaps it is no good.
3. The rear limiting valve probably is kaput, though it was reconditioned or replaced some time in the last 15 years. (yeah, not exactly mint condition.)
4. Most of the hoses have been replaced already by me, but I will double check that I have not missed anything...

So, where to from here? Nothing obvious is jumping out to anyone, so I am inclined to just start replacing stuff with new bits, on the basis that this can't be a BAD thing. I will see about adjustable rear limiter vs reco, like the idea of something new if I can.

Regarding the booster... there is a HUGE price difference between the VH40 and the VH44. Given the VH44 was previously giving enough boost for his kind of driving (he's an extremely conservative driver thanks to his various levels of flight training.), is there any reason NOT to get another VH44 aside from boost levels? The car is used almost exclusively as a daily runabout and would rarely go over 60 km/h.

If I can source an aftermarket limiter, can anyone point me in the direction of data on the pressure settings for the genuine article?

Also, I would like to replace the master cylinder completely, aside from the usual European suppliers, can anyone recommend a local (Australian) supplier?

Matt
 
Dijon16 said:
I had a 1970 404 with the problem of the rear drums locking under heavier-than-usual braking, and the back wanting to overtake the front.

It turned out that the proportioning valve had the lines connected in the wrong position, which I think gave it some kind of bias.

Can't remember all the details, it was 40 years ago.
Click to expand...

Yes, that would do it, but I am confident that I have not changed the position of any of those lines in this case, so the problem of jamming must be something else.
 
robmac said:
I'd be taking a good look at the master and the flexible hoses then.

The hoses can can be economically reproduced by any brake shop with a Brakquip hose making machine.

The 404 hose ends are a standard off the shelf fitting. Just take the original hoses to the shop.

You can even have road legal braided hoses in lieu of standard neoprene. :eek:
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Thank you for this, I will follow it up. Repco also had a listing of some compatible hoses from a few of the H series Holdens that matched.
 
so I am inclined to just start replacing stuff with new bits, on the basis that this can't be a BAD thing.
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Chasing rainbows is NOT a good idea & simply wasting money.
Especially replacing good parts with similarly good ones.
We have been told you have done something with the master cylinder, booster &/or brake lines.

Things like replacing brake hoses is last on anything like this as they were not interfered with & can easily be eliminated from the brake circuit 1 by 1, if suspected of being crook. BTW they do have a service life & it is not 30 or 40 years!

Forget the guessing [or following unqualified guesser's] & start diagnosing.

Suggest this process would be easier for yourself, & those trying to assist, if all the symptoms were listed then ticked off as eliminated. Currently all symptoms are commingled & thus hard to address logically.

This is most likely something/s that has/have been introduced/replaced by work that has been done on the brake system recently.
So first thing to eliminate as a possible contributor is the foreign to this system is the hydrovac.

1. Test the hydrovac is functioning.
Switch off engine & pump pedal then hold.
Start engine & pedal should feel softer/sinking when engine vacuum assist to the hydrovac is received.
2. The VH40 & 44 came in different setups primarily for single circuit master cylinders.
2a. Front & rear circuits will be divided after coming out of the booster & when fitted with rear drums there is a possibility a residual pressure valve & pressure differential valve will be fitted in the rear circuit/s.
2b. The bore sizes can be larger/smaller from the original booster giving difference in pedal travel & effort.
3. Inadvertently interchanging brake lines front to rear will give a rear brakes locking up before front symptom.
This is because most braking force is meant to go to the front.

Let's know what you find but if unsure take the hydrovac to a brake specialist for testing/checking.
 
I have recently gone through the same thing on my 69 404 .my pedal went to the floor at a roundabout ,although the rear wheel cylinders looked ok ,when i pulled the rubbers back there was fluid seeping ,i replaced the cylinders and fitted a portioning valve i had had reconditioned ,all bled the pedal was crap ,the brakes jammed up and i could only force it to drive in reverse ,.the boost had been only just sufficient since i had the original completely rebuilt by better brakes ,i found the boost problem was due to the vac hose collapsing internally at the manifold end ,i got a 3 way junction from the brake place ,fitted it in place of the portioning valve ,blew the dust out of the rears ,bled again ,all is fine now with acceptable boost ,,i intend to swap the valve back in and see what happens ,as im not convinced it was the problem ,no matter what i did i couldnt get the spongy air in the system feel ,on the pedal till i removed the valve ,suspect there was air in it ,as i am now using it as a daily ,im having difficulty finding the time ,and i can only lock the rears when braking savagely , prior to this everything in the system had been replaced or re built except the rear cylinders ,calipers ,master hydraulic hoses ,portioning valve ,were done ,so all i can contribute is check the vac hose ,and swap out the valve with a three way ,to eliminate that as a problem ,at the time i suspected it must have had an air pocket in it ,causing the spongy pedal ,pugs
 
A lot of good info in this post.

I've added some page breaks so members will find it easier to read. :D



I have recently gone through the same thing on my 69 404 .

My pedal went to the floor at a roundabout ,although the rear wheel cylinders looked OK ,when I pulled the rubbers back there was fluid seeping .I replaced the cylinders

And fitted a portioning valve i had had reconditioned ,all bled the pedal was crap

The brakes jammed up and i could only force it to drive in reverse .

The boost had been only just sufficient since i had the original completely rebuilt by better brakes ,I found the boost problem was due to the vac hose collapsing internally at the manifold end

I got a 3 way junction from the brake place ,fitted it in place of the portioning valve ,blew the dust out of the rears ,bled again ,all is fine now with acceptable boost.

I intend to swap the valve back in and see what happens ,as i'm not convinced it was the problem.

No matter what I did I couldn't get the spongy air in the system feel ,on the pedal till i removed the valve ,suspect there was air in it ,as I am now using it as a daily ,I'm having difficulty finding the time ,and I can only lock the rears when braking savagely

Prior to this everything in the system had been replaced or re built except the rear cylinders ,calipers ,master hydraulic hoses ,portioning valve ,were done ,so all I can contribute is check the vac hose ,and swap out the valve with a three way ,to eliminate that as a problem

At the time i suspected it must have had an air pocket in it ,causing the spongy pedal

,pugs
 
Lots of pillar to post stuff going on & not diagnosing!
That being said:

It is very unusual for the brake pedal to go to the floor without progressively becoming worse.
This 'progressively worse' is from lack of brake fluid, caused by leaking components, depleting the reservoir of fluid.

Brake pedal going to the floor [& the reservoir level being OK] is generally related to a master cylinder primary cup fail/ing/ure issue.

I've seen this in a number of older vehicles where the little brass shim was left out, somewhere along the line, between the primary cup & piston.
The cup after years of operation resembled a bottle top.

When the brakes are applied the closed brake system just doesn't close & the pedal goes straight to the floor or slowly sinks to the floor on hard application or standing @ a stop light with brakes on, for example.

Bleeding air when a proportioning valve is in a brake circuit can sometimes be problematic, primarily as they alter fluid pressure between circuits.

I would never recommend pump bleeding brake systems due to problems it can cause particularly with old non refurbished brake parts.

Here is one good inexpensive [cheap old mechanical fuel pump] vacuum method I employ that will work from longest to shortest line.
Use liquid teflon or thick paint around the bleeder if drawing air from there....when trying to pull the vacuum....

PC290268.jpg

Here is another method:
https://www.youtube.com/watch?v=Af0SYcbzIbo
 
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OK, I've read all this.

Just to be clear, the car is NOT losing brake fluid. There may well be some bypass happening on the master cylinder, but it passes every test I can throw at it in terms of maintaining pressure. It does appear to be needing to fill some other area of the system before it can do its job properly. And whatever it is doing, the fluid is (eventually) returning to the reservoir.

I have done a lot of work on old car brakes in the past, so I am kind of shocked to discover that I cannot figure this one out without help. There have been some good suggestions here which I will follow up, but at this stage I am getting the impression that I am going to have to spend my way out of this a little. My hope that someone would come up with a "you've forgotten to twist the XYZ thingumy" solution was a long shot, but worth a try. I think the closest I can get to that would be the focus on the rear pressure limiter, not least because Robmac's description of his problem is so very similar to what I am seeing.

I think I will start with Robmac's suggestion of temporarily removing the pressure limiting valve at the rear, as it is a cheap and simple solution.

The job is tricky, I am forced to juggle multiple variables brought about because of the sequence of events and the multiple unknowns.

1. I do not know how long it took for the extra travel problem to develop, as my son didn't really notice it. (Insert face-palm emoticon here.)

2. I do not KNOW the condition of the VH40 booster or the original VH44.

3. I do not know the condition of any of the parts, really, except maybe the master, which I have pulled apart and looks very good.

I really liked the spray bottle idea, did not expect that to work as well as it appeared to do, so I will give it a try.

Matt
 
Matt: How to adequately test the hydrovac was enunciated earlier & try bleeding properly before pulling anything apart, would be my suggestions. JG.
 
Gilow said:
OK, I've read all this.

Just to be clear, the car is NOT losing brake fluid. There may well be some bypass happening on the master cylinder, but it passes every test I can throw at it in terms of maintaining pressure. It does appear to be needing to fill some other area of the system before it can do its job properly. And whatever it is doing, the fluid is (eventually) returning to the reservoir.

I have done a lot of work on old car brakes in the past, so I am kind of shocked to discover that I cannot figure this one out without help. There have been some good suggestions here which I will follow up, but at this stage I am getting the impression that I am going to have to spend my way out of this a little. My hope that someone would come up with a "you've forgotten to twist the XYZ thingumy" solution was a long shot, but worth a try. I think the closest I can get to that would be the focus on the rear pressure limiter, not least because Robmac's description of his problem is so very similar to what I am seeing.

I think I will start with Robmac's suggestion of temporarily removing the pressure limiting valve at the rear, as it is a cheap and simple solution.

The job is tricky, I am forced to juggle multiple variables brought about because of the sequence of events and the multiple unknowns.

1. I do not know how long it took for the extra travel problem to develop, as my son didn't really notice it. (Insert face-palm emoticon here.)

2. I do not KNOW the condition of the VH40 booster or the original VH44.

3. I do not know the condition of any of the parts, really, except maybe the master, which I have pulled apart and looks very good.

I really liked the spray bottle idea, did not expect that to work as well as it appeared to do, so I will give it a try.

Matt
Click to expand...

A final thought 404s are known to develop free travel in their brake pedal linkages. This can manifest as lost travel when pushing the brake master.

A quick look at possible wear in brake pedal linkages may be worth a look.
 
404s are reknowned for the pedals to seize on their shaft. If the brake pedal doesn't return fully the master cylinder won't work as it should. Get under the dash and by hand check that the pedal returns fully without friction. If it is stiff you need to pull the complete pedal assembly out, knock out the shaft (without breaking the alloy housing) and clean and grease everything. You won't be able to simply spray with WD40 to fix it.
 
Artificer said:
Matt: How to adequately test the hydrovac was enunciated earlier & try bleeding properly before pulling anything apart, would be my suggestions. JG.
Click to expand...

Well, it's a bit late for that I'm afraid. As I said in my original post, I have actually SWAPPED the boosters. AND dismantled and inspected the master. AND bled the system.

The boosters are both behaving perfectly in testing, this feels like something different, certainly something I have not met before. So much esoteric knowledge in any car, I think, from the advice here, that the regulator at the back is the next logical step. Simple enough to eliminate.
 
Gilow said:
I have done a lot of work on old car brakes in the past, so I am kind of shocked to discover that I cannot figure this one out without help.
Click to expand...

I just got a flash of Schadenfreude. The same has happened to me twice recently, and I still have the second problem.

The important things are to do things methodically and prioritize them, don't let it all stress you out, and leave a bit of time between each step for your mind (even your subconscious) to mull it over and pop up a solution.
 
Beano said:
I just got a flash of Schadenfreude. The same has happened to me twice recently, and I still have the second problem.

The important things are to do things methodically and prioritize them, don't let it all stress you out, and leave a bit of time between each step for your mind (even your subconscious) to mull it over and pop up a solution.
Click to expand...

As well as persistence and maintaining self confidence.

I spent almost an hour yesterday diagnosing a fault in an electronic project I had just built. Only to discover I'd installed an LED backwards. :nownow:

The fault was found without test equipment and solely by careful inspection.

I was most deflated after finding it. :crazy:
 
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