Vacuum hose and check valve source?

I'd say that either could be a problem (sticking closed check valve or leaky hose). Have you tried just disconnecting the vacuum hose at the brake booster to just see if any vacuum at all is reaching the booster when the engine is running? If none (and it's accessible), you can disconnect on the upstream side of the check valve to check there, too (and, with the check valve in hand, to some "blow-thru" tests to see if that's working properly).

Is this an automatic or a 5-speed? -- the auto seems to have a much more complicated vacuum system that could have other problems.

 

On an automatic you also have a supplementary vacuum pump on the right cylinder head.
CIS equipped cars make little manifold vacuum and the 400/412 was always an issue with the power brake vacuum supply. The automatic cars tend to shift to the highest gear at pretty low speeds so in many instances there is very little RPM and very little manifold vacuum. The pump was supposed to fix that.

The hoses are old enough and as I recall are all fabric covered Id probably just replace them all, test the vacuum check valves and test the vacuum pump operation. Its been a long time since I have worked on one some of it is hard to remember but I recall it also had an electric pressure switch mounted near the booster. Many were disconnected because people got tired of the warning light indicating low system vacuum. Also the boosters do go bad and that is the symptom.

 

It's meant to be much "harder" than the usual hose (so it doesn't collapse under the vacuum). I'd still suggest that measuring the vacuum in a few places before deciding what to do, and Brian's suggestion to maybe test the brake booster to see if can even hold a vacuum, would be the first diagnostic steps -- if it doesn't have an obvious hole rusted thru the metal outer case .

 

The injected manual cars have the vaccum pump on the front of the right head.

Replacing vacuum hoses never hurts but unless they are cracked or leaking it is unlikely to fix the problem. The advantage of new hoses is that they seal on the fittings better.

Apart from leaks or blockages on any of the vaccum hoses I’d be checking the one way valve, they can often benefit from a clean or replacement. (Should only be able to blow through it the one way).

The final check is the pump, they are lubricated with engine oil and they can get a little leaky and even block the vacuum hose with oil in extreme cases. They have little composite blades in the pump which wear on one shoulder, these can be taken out and installed in the opposite orientation so they wear/seal on a new shoulder. This can increase the performance of the pump if they have worn unevenly.

 

Pretty sure all of these cars have the vacuum pump.

 

I struggled to find a replacement check valve. I removed the old one and it was sticking shut. I used some WD40 and got it working freely. I later found the part and will post supplier when I dig it out.
Ken
p.s. Tom Vail has one at an outrageous price. I think the Fiat/Alfa folks have it for less.
https://www.allferrariparts.com/pn128435id135279.html
Visually different but I think the fittings are correct size (?)
https://www.awitalian.com/product/brake-booster-check-valve-128435a.html/
Correct part at a better price:
https://www.ferraripartsexchange.com/products/brake-pipe-servo-non-return-valve-p006

 

If you really need a Ferrari branded part.

https://www.ricambiamerica.com/car-diagrams/ferrari/v6-v8/360-group/challenge-stradale/brake-booster-system/193186-non-return-valve.html

Its pretty generic. Can probably find one in most parts stores.

 

The system will operate every bit as well as any other Ferrari power brake system if it is working correctly. I explained some of the challenges to make it work well. They are not excuses why it cannot work well.

I have driven a lot of those, and driven them a lot. They work great. You just have to fix it.

 

Yes it would be easy for this hose to get blocked as it has a very small orifice in the connector at the oil filter housing end (be sure to refit this or you will have too much oil supply to the vacuum pump). The advantage of the orifice at this end is it means the hose is not under pressure and low pressure hose can be used to replace it as the fittings are rebuild-able.

I replaced my vacuum hoses a few years ago and struggled to find replacement hose that large until I found a place that did truck vacuum brake hose which was the same size.

Cheers,
Al

 

Years ago my 1980 400i was lacking vacuum from the vacuum amplifier to the t400 tranny..turned out that the hose was routed near the exhaust and had melted the hose..I replaced the long hose with metal tubing with a section of vacuum tubing with a section of rubber hose to the fitting on each ea
on each end...perfect. Jacques.

 

If you mean this one, I had it made at a marine hose shop for 10$. Image Unavailable, Please Login

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The shop reused the same fittings I had.

Could you explain how you switched out the vacuum pump part that wears out?

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Thank you. Note also there is another check valve, one up by the vacuum booster.

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Is this similar to the little air pump for the horns?