355 Teves hydraulic brake delay valve leak

• That thing is basically a proportioning valve. Does anyone know the ratio? I know there are a number of racing valves that can be adjusted that would do the equivalent if we knew what to dial in. One other thing. In your picture it looks like your leak is coming from what looks like an o-ring on the left fitting. Anyone ever have one of these disassembled?

 

What's the Ferrari part #? I can probably help you if you provide that.

 

Aside from trying the usual suspects (T. Rutlands, Eurospares, etc.), the cheapest available - though used - seems to be here. It does appear to be in excellent conditions.

Sorry, couldn't find any silver bullets with this part (i.e. cross-reference beyond Jaguar).

 

According to the Jaguar manual, this valve limits the fluid pressure on the rear brakes. This is necessary because the rear brakes are operated directly by the fluid pressure coming from the ABS pump, via the modulating valve inside the MC, and not by the MC piston. If it is bypassed, there is a risk of rear brakes locking. I am sure that the Jag and the Ferrari valves, although look identical, are set at different pressures (different rear brake pistons, pads and rotors, different weight distribution etc.).

I have tried to separate an old valve from a Jag at where the O-ring sits but it is not possible. The Jag forums also confirm that it is not separable. Some say that on a Jag, the BMW valve (Ate) can be used, p/n 34-33-1-152-494, but I doubt its pressure setting is suitable for 348/355.

https://www.fcpeuro.com/products/bmw-abs-pressure-regulator-34331152494

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Looking at the Jag forums, the o-ring just covers some weep holes.

If you try to disassemble the valve, the Jaguar forums pointed to this generic valve video (including some warnings on where to apply pressure). Skip the first 5~6 minutes.



There are some real horror stories if these valves break (not just from the perspective of brake lockup).

 

If you don't want to spend big money on a genuine Ferrari one, you can try (as suggested) using an adjustable brake proportioning valve. Here's a very compact one but with 1/8 NPT threads (you can get adapters to convert to metric):

https://www.ebay.com/itm/Speedway-Compact-Adjustable-Brake-Proportioning-Valve-/133374154828

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You can then try different setting until you are happy with the braking behaviour. If you get the ABS kick-in when not really expected, it would mean too much pressure on the rears and just back the regulator off a bit.

 

Parts collector has a new value for the low price of 2400.00 USD

These are used on club racers, 911's and BMW's and are available in metric.

Let us know when you confirm the thread pitch and size on the lines.

https://www.pegasusautoracing.com/productdetails.asp?RecId=10257&utm_source=google&utm_medium=cpc&utm_campaign=OBP-BV01&gclid=EAIaIQobChMIj62OoI7c6wIVjLbICh22hQTHEAQYCCABEgKfj_D_BwE

https://www.pegasusautoracing.com/productdetails.asp?RecID=4889#:~:text=A brake proportioning valve allows,outlet ports with concave seats.

 

https://www.ferrarichat.com/forum/threads/rear-brake-pressure-stuck-not-hoses-nor-calipers.625057/

 

It makes sense given that the Jags and 348/early355 used the same abs pump as well. Let us know I bet it works great.

 

There are two devices here, called in the Ferrari catalogue "Delay Valve" and "Valve Corrector" (Pressure Regulator?):

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I have a Jaguar delay valve which also has "8.5" stamped on it. I don't think it is related to pressure as this thing is called "Delay Valve" or "Pressure Delay Valve". The thing on the right should control the pressure. Identical looking unit is used on certain BMW E30-s and it is called "Pressure Regulator" or "Pressure Reducing Valve":
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This BMW pressure regulator has "5(arrow)25" stamped on it and the Ferrari unit has "5(arrow)20" so it appears that they a set at different pressures.

On the other hand, a document that I have on the Jaguar Teves ABS system states that the "Pressure Reducing Valve" maintains pressure differential of 6 bar [87 psi] between the front and rear circuits but, in the parts diagrams, the Jaguar unit is shown as a Pressure Delay Valve, same looking as the Ferrari "Delay Valve" and Jaguars do not seem the have a Pressure Regulator like the BMW one.

So, it is a bit unclear which unit on the Ferrari does exactly what. Following the description, I would understand that the "Delay Valve" just delays somewhat the application of pressure to the rear brakes as it is applied the moment it is applied to the front brakes master piston. Some delay is needed to the rear brakes to give time to the front brakes master piston to move and start applying pressure to the front brakes. And the "Valve Corrector" should actually be a pressure regulator (limiter) to prevent too much braking force on the rear brakes that are operated directly by the hydraulic pressure of the system.

 

I found a nice clean one from a jag, when I get it I'll run it in ultrasonic cleaner and low pressure air then throw it in my parts box. When I put a BBK on next spring with SS lines I will probably put it on and take the old one out, clean it and store it. I have seen 2 of these have issues past few months out here and they are NLA.

Btw I read on Jag forums that a the bmw one was used a few times even though the spec is not the same its close. The Jas had the same pressure as the Ferrari so if it worked on the Jag it may work on these cars. The rear brakes may either bite sooner or later however depending on how the pressure works.

 

I don't think there is any problem using a Jag Delay Valve. This thing seems to be part of the Teves braking system, related to how the MC operates, and, I believe, it is there to equalise the start of pressure application between the front and rear brakes and not to bias front-rear. Since the MC-s and the working pressures are the same Ferrari-Jag, this device should be the same on both (and both, Ferrari and Jag, delay valves have the number 8.5 stamped on them). On the Jags, the delay valve is placed next to the ABS block in the line that goes to the rear brakes.

I have seen the Jag post about replacing the delay valve with the BMW valve but I don't think it is a good alternative as the BMW valve is a proportioning valve, not a delay valve.

I think it is the second thing on the Ferraris, the round thing connected to the delay valve, what does the proportioning. The number stamped on it is 5(arrow)20. I have read about Lotus proportioning valve which is marked 3/15. According to the Lotus forums, these numbers mean that up to 15 Bar, there is no proportioning. Once the pressure exceeds 15 Bar, the proportioning starts and pressure on the rear brakes is being kept at 30% (number 3 in the valve marking) of the front brakes pressure.

Following the Lotus valve marking, the meaning of the 5(arrow)20 on the Ferrari valve may mean no proportioning up to 20 Bar and thereafter the rear brakes pressure is kept at 50% of the front pressure.

Similar looking valves for BMW have numbers 5(arrow)25 and for Porsche 944 5(arrow)18.

BMW:
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Porsche
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As to the delay valve, Mopar (~USD 35) has similar looking valve as the ATE one, used in Chrysler Cirrus, Dodge Stratus, Plymouth Breeze 1997-2000.

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I assume you meant to

I assume you mean to type CBC4233 and not CBC4223.

 

I "tested" my Jag delay valve by blowing through it - in the direction of he arrow, there is a fare bit of restriction to the blow and, in the opposite, quite free. The only thing I could see inside the valve is a tiny steel ball. This is probably the check valve that allows free flow in the opposite direction (brake pressure release).

When you get your Jag valve, can you do a similar blow test and let us know. I would like to compare my test with another valve to know whether my valve is good or not.

 

I believe there is a spring and some xrings in there that pushes and seals against the arrow direction, I have seen rebuild kits for American models and those had those parts at lease not sure about the jag but there has to be a spring and I suspect they disintegrate over time. But yes definitely plan to make sure the mechanism is free. Will let you know.

 

There is a set of both valves (used) on Ebay, if anyone wants to keep spare - https://www.ebay.com/itm/Ferrari-348-Brake-Pressure-Regulator-With-Rear-Brake-Line-P-N-136313/133225576595

 

I got my new delay valve and I have a new pressure regulator coming from England.
The delay valve, I can insert a thin hex key shank down the fluid port and push. On both ends I do this ad there is a spring loaded valve on both ends when you push against it. It appears to be a 2 way check valve of sorts.

I tried separating the 2 halves but it was stuck and at the risk not not being able to tighten it back up and having a leak, I left it.
I can actually blow air through both ends as well one end is easier.
I will be filling it with brake cleaner (depress ball and fill) and running it in an ultrasonic cleaner and blowing it out with compressed and repeat in many cycles air for 8 hours or so. I will do the same for the regulator when I get it. When I do brakes and lines in the spring I will replace those 2 and clean the old ones and store them for future.