Suzuki "vacuum pump check valve" recall and brake failure - technicals ?

[Superflan]

Hi,

Wife's MY19 Suzuki Vitara had a very hard ineffective brake pedal on Sunday. That issue can come intermittently and is very rare, but imagine it popping at the bad place in time...

Then we reminded we had a recall letter from Suzuki about this, and we forgot to turn into dealership to sort it out. I believe it's this recall campaign "97G5" but not exactly sure.

This is the recall letter we got. It essentially says they some vehicles are affected by a faulty vacuum pump check valve that could potentially reduce braking assist and present a stiff brake pedal.

While the car is booked in on Thursday, I'm not sure I'll get a positive outcome first hand, since the service advisor told me they have to check first if the part is faulty or not. I went to the parts counter but the part didn't seem to be in stock. It can have a two weeks delay for delivery if ordered. Saw this part number 51280-61M00 for a price of €247

So I got home and started searching the web.
Found pics with the Bosch reference written on the part, 0265005336 -- and indeed looked on what would have been the check valve for me, I see this.

Amazingly this is also found on McLaren 520/720 around 2020. but how much of a sensor it is, and how much of a check valve it is? Do you think there's a check valve on another location? In the vacuum pump itself?

I've stumbled upon threads of other cars where this vacuum sensor could do the exact same thing: give a hard brake pedal to the point where you can't realistically break, and I understand it does something to the ABS pump and that's why it can get the pedal impossible to press.

While I understand it's not a good idea to mess with braking system, is there a possibility of running brakes and ABS without the vacuum sensor, fitting a dummy/emulator? saw this on trucks for hydrobrakes conversions but wondering. How to get rid of that point of failure?

 

[KrisZ]

Googling this Bosh part number returns a description of either a sensor or a valve. It does have three wires, so it can likely be both.

You could try to put an elbow there and run straight vacuum to the booster. But it will likely set a code. The system may even turn off the ABS or traction control, but the brakes will have a full assist.

 

[mk378]

Does the hose go to the intake manifold, or to a vacuum pump? On older designs where it goes to the manifold, the fitting there is a check valve to retain vacuum in the booster in case the engine stalls or otherwise manifold vacuum decreases.

 

[Superflan]

Does the hose go to the intake manifold, or to a vacuum pump? On older designs where it goes to the manifold, the fitting there is a check valve to retain vacuum in the booster in case the engine stalls or otherwise manifold vacuum decreases.

The hose goes straight out of the "sensor" to vacuum pump. Since it's a 1 litre turbo, there's no real natural vacuum available.

Figured the sensor could simply be to restart the engine when in a-stop mode when you pump brakes and there's a low vacuum situation. I long disabled the start&stop using the hood sensor so I forgot it might be that.

You could try to put an elbow there and run straight vacuum to the booster. But it will likely set a code. The system may even turn off the ABS or traction control, but the brakes will have a full assist.

Do you think the assist could be modulated depending on the vacuum? Since it's a mechanical vacuum pump at the end of one camshaft and no electronics on it, I guess not.

Is there such a thing as too much vacuum in a brake booster that can break something?

 

[mk378]

The sensor would also be a check valve if there is no valve in the pump. If it gets stuck closed, there would be no power since the booster would not see any vacuum. if there is a leak anywhere the system would also not work.

You could probably use a regular check valve if the replacement part is not available. I don't think that a simple straight through pipe would work.

Is there such a thing as too much vacuum in a brake booster that can break something?

No.

 

[Superflan]

I then discovered there's a possible SKU for the supposed recall reference:

Can't find much information about that, but I guess it's an internal check valve in the vacuum pump. Doesn't mean that the sensor isn't also a check valve

I guess I'll have to wait for the appointment and post results. But it's nice to learn how those things work

 

[KrisZ]

You likely need this part. Like I said, there are three connections coming from it, usually the third one being a signal for the ECU feedback, so it knows when it has been activated/deactivated.

For what purpose it is used? Not sure, you would need to find a factory repair manual that goes through the troubleshooting steps that involve this particular component.