Brake Valve - Rear

Good day All,

I have been slowly working on my 365 and in the process I was reviewing the rear brake proportioning valves (Part 105041 - Item 7 is the attached pic). From my Internet searching it appears that these valves are used only on the 365 cars (including daytonas, C4's, etc) and there are no rebuild kits available for them because of how they are designed. With that said I was curious if any of you have dealt with these valves and if so what you ended up doing (replace, clean up, or used something else, etc).

Thanks in advance!

Cheers,

Sam

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This valve looks similar/ identical to what Alfa used on front transmission 105/115 series (1750 / 2000 Berlina, GTV and Spider). Both the Berlina and GTV ended production in the mid 70’s, the Spider soldiered on till 96 if I recall correctly.

I was the Parts Manager at an Alfa / Ferrari dealership for close to 20 years and can never recall one being replaced. Try Centerline in Colorado or else AFRA in Milano if Maranello Concessionaires no longer stocks them.

 

Good day Gregg,

Thanks for your response! From what I read these valves are made by Ate, but that they were spec'd by who ordered them. Sadly, I have not found the specs and so it is possible that the spec's could be different depending upon the car manufacturer and the car's model. The parts appear to be available and so it does look like I can order them from the usual suspects, but was curious to find out more info on them and/or how one could test them outside of actually using them on the car (my brakes and suspension are no longer attached and so testing them on the car is a no go). I also wanted to see if these items do fail over time and if so I would simply just replace them. Your last comment is anecdotal that they were not an item that usually needed replacing.

Cheers,

Sam

 

Good day All,

I found out some more info on these valves... Below is taken from the C4 Workshop manual

So... these valves are not proportional valves, but affect how or by how much the rear brakes are applied during braking. Effectively they regulate if/when/and how much rear braking is applied in a braking situation... Given what these units do and given that they involve safety (e.g. brakes) I think I will just replace them and be done with it.

Cheers,

Sam

 

Good day,

I found more info from a site that directed me to a Ate document on the operation of these valves:

From Ate:

So... modifying my earlier summary... These valves limit the brake pressure on the rear brakes to a point where any additional pressure is limited to the designed limits of the valve. In other words in hard braking the rear brake pressure will increase to a limit (and thus potentially preventing the rear brakes from locking), whereas, the front brakes will continue to increase brake pressure. Here I presume the reason is to maximize braking to the front brakes and to ensure greater car control during hard braking conditions.

Cheers,

Sam

 

Maranello and Autoepoca appear to stock this part

 

Good day Jean-Michel,

Indeed, I posted earlier that the part appears to be available from the usual sources. I sent off a few e-mails to verify this, but given the Covid-19 issues I suspect it will be a few days or so before they respond. I will follow up with the availability once I hear back.

Cheers,

Sam

 

I don't know why they went to a more elaborate limiter on that series vs the boxer, 308, dino unit.

As we discussed before I just bought some rebuild kits for the simpler version for $10 US a valve. I would open the valves you have and look inside before replacing them. Best case scenario you clean them out and replace the copper washer. For 300 euros a piece its worth looking inside.

 

Good day Paul,

Hard to say the reasoning behind using them. Some C4's have a slightly different version and apparently other versions were used on some British cars as well. Since they were not used on the later and more powerful cars one could conclude that they were not as effective as they thought?

I will certainly crack them open when I remove them from the car and see how they look inside. If the seals look OK and/or I can find some suitable seals I may simply refresh them and reuse them now that I know what they are supposed to do... and having a bit of data from the workshop will allow me to do some basic testing on them. That being said I will post up some internal pics when I get them apart.

Cheers,

Sam

 

Those particular units are indeed quite different to the 400 valves. I sourced a used missing valve for my 400 from GT Carparts at a very reasonable price much less than $300. I wouldn't be surprised if he has other used ones for 365 and 400 floating around. I had them overhauled along with my calipers and master cylinder. The shop that did it here had no issues at all, and from the outside, it seems they've done a good job. I'm a fair way from testing though.

 

The simple ones on the other models consist of a heavy coil spring with a piston on it and a round about way for the fluid to get to the other end. There's 2 lathe cut seals and one copper washer.

 

Good day Tim,

Thanks for the post and the info! If you get a chance and if it is not too much trouble, can you post up a pic? I am simply curious. Sadly, I have a never ending desire and curiosity to learn how things work and so I spend way too much time on things like these. However, I enjoy these little tangents,as it allows me to satisfy my curiosity and also in the process I continue to learn about things that I never really thought much about.

That is also good news that you were able to have them rebuilt and so this adds to Paul's comment to do the same if possible.

Cheers,

Sam

 

Good day Paul,

I suspect this one is quite similar. I saw a drawing of a similar device, but cannot find it for the life of me. No matter, I will post up the guts of the unit in the next day or two.

Cheers,

Sam

 

Here you go Sam. This the best I can do under lockdown. Unfortunately I don't have any pics of it's internals Image Unavailable, Please Login Image Unavailable, Please Login

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Good day Tim,

Thanks for the pics! Indeed, the 400GT valves are a lot different than the 365 version. This is what mine looks like on the car.

I will post some pics of the internals shortly.

Cheers,

Sam

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Good day All,

I finally had some time and removed one of the valves and dismembered it. Below are the pics. Clearly, the valve is made by Ate, as it is cast into the housing. The crud looks to be from breakdown of the originally painted housing. Given that it is common knowledge that brake fluid is corrosive to paint, I suspect the lower wiper seal was leaking brake fluid into the spring chamber and thus coming into contact to the painted casting protrusion.

The bottom portion contains a spring chamber which has an adjusting nut/pin that looks to be epoxied in place. This pin controls the spring tension which pushes against the spring which pushed against an internal Aluminum piston with internal passageways that appears the regulate the brake fluid from the master cylinder to the both the left and right rear brake caliper's 2 pistons.

The piston has three seals where one is a sealing o-ring between the brass cup and the casting. The second is an o-ring between the brake fluid inlet and the two outputs. The third is a wiper seal between the spring and the brake fluid inlet. The top of the piston has a spring loaded plunger assembly that I have yet to take apart. I am working through the logistics of how this assembly works and will post up my thoughts once I have checked a few more items.

The positive side is that the piston and casting bore show no wear or pitting and so I think they can be reused providing I can source replacement seals... which will be my next task.

Cheers,

Sam

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Hello Sam, great pictures, thanks, I found this page from the alfabb showing a valve which resembles your example:

https://www.alfabb.com/threads/rear-proportioning-valve-105.152693/

Interestingly (item #3 20 June 2009), the user had to cut a new square gasket.

 

Good day Jean-Michel,

That is a great link and it looks pretty close to identical to the 365's. My guess the only difference will be the "setting" of the spring pressure and possibly the internal pressure valve located on the upper portion of the piston. Since I am not going to alter these, all should be fine.

I reached out to another f-chat member (TTR - Timo), as he mentioned that he rebuilt these valves when restoring a Daytona and so he is checking to see if he has the info on the wiper seal.

I will certainly post up what I find.

Thanks again for the link!

Cheers,

Sam

 

Thanks Sam, I am eager to read the results of your findings. I have two 365's locked up in a place which I cannot reach due to current confinement rules, I am sure their valves are overdue for maintenance on them!

 

Good day All,

I reviewed the thread that Jean-Michel provided and found some excellent info. Firstly, the brake limiting valve looks to have been also used on old alfas as well. The thread pretty much mirrored my efforts on this and found that the o-rings are not too tough to find (sizes of 26x2mm and 12x2.5mm), but the wiper seal was a challenge. The thread starter, who is in Australia, found the seal at a brake part supplier and was offering them to whoever wanted them. Sadly, this was in 2009 and since then the seal supplier no longer has them.

Digging deeper and following a few other links/threads I found:

a. Other old Alfas have very similar valves as Tojo(Tim) needed for his 400 GT (See pic - Taken from Classic Alfa's website). I am unsure if the 400GT valves are factory adjustable like the 365 valves and so one would need to investigate this further. If anything, one could use the alfa replacement for parts to rebuild your originals.

b. The Porsche 914 cars use the same Valve as the 365 with I suspect different factory settings. The Porsche valve is available from a variety of sources with one being PMB that has been referred to in many threads on Fchat for Ferrari brake caliper rebuilding. PMB can rebuild the valves for $169 USD (https://www.pmbperformance.com/914-brakes/Early_Pressure_Regulator.html) and even offer a rebuild kit with the seals for $59 USD (https://www.pmbperformance.com/914-brakes/Early_Pressure_Regulator.html).

PMB describes the functionality of this valve that correlates to the info I found within the Ate and C4 Service Manual, but does it in a more straightforward manner:

I am going to continue to look for the wiper seal and if unsuccessful I can always purchase the seal kit from PMB. That being said I will continue to add to this thread until I have my valves refreshed/restored.

Cheers,

Sam

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Good day Jean-Michel,

You are most welcome and thanks again for the link!

Given what these valves do I think it is important to inspect them to ensure that they are functioning properly and/or not internally leaking. Thankfully, the one I removed on my car did not look overly bad and/or worn, but did show signs that the wiper sealing was allowing some fluid to pass into the spring chamber. Closer inspection of the seal does not show any degradation, nicks, etc and so it is possible that the seal weep could be because of the extended time of no use (and thus not enough pressure against the seal lip and the bore) or a tolerance change because of the temperature differentials where I am at (-23C today!). I will remove my other one this weekend and will inspect its condition and will report back.

Cheers,

Sam

 

10C here today, sat outside after work and enjoyed the sunshine.

 

That is just plain nasty... we have not seen +10C since last Fall... We did get to around +7 a few weeks ago for a day and then Winter jumped right back in. This past weekend we had temps close to -30C. Argh... The only good part is that one has a great excuse for not doing any outside or any other yard work

Cheers,

Sam

 

Nasty ?

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Never saw such a warm April, and we've got to stay home...

Back to the subject, My rear wheels do tend to lock. I've put some fresh brake fluid and with a bit of luck this will solve the issue... unless the valves are faulty(?)