Bad master cylinder?

Truck seems fine today.Toyota tech said it couldve been an air pocket that worked itself out. Neither he or I could duplicate it.

 

Is this the seal you’re talking about and if so, would that seal cause a whistling sound (like a dog chew toy being squeezed) when the pedal is pressed firmly?

Thanks

 

Yes that is the seal. It could be that or the diaphram in the booster. I have yet to find a replacement for that seal.

 

Thank you Glamisman. I've been out catching up on much needed maintenance on the old girl till now, just seeing you'd responded.

So here's the odd thing with mine. I pulled the master cylinder out of the booster in preparation of pulling the booster to send it out to get rebuilt, and during that time I found that I should pinch off the vacuum hose to see if that would isolate the sound and the booster...so I put it back together, started it up (without pinching off the vacuum hose), STOOD on the pedal and...it didn't make a sound.

That seal that the master cylinder goes through actually had a torn flap, and that's why I replied to your post, figuring that I might be on to something if that seal was the one you were talking about. I'm learning as I go, but I don't know how to make sense of this, based on what (I think) I've learned. I thought for sure that the booster was going to be singing again.

The pedal feels fine too.

Can you help me understand what's going on here? Thanks again for responding in the first place.

 

A little confusing, if you are talking about the paper seal between the MC and booster I cut one out of a cereal box. Worked perfect.

 

Nope, it's the rubber one in the booster itself, that the MC goes through. Can see that it's damaged around the upper edge in the picture.

 

This guy...

 

It's pretty unbelievable that this seal isn't available. I'm seeing them for other boosters.

 

If you find one please post a link. My search was maybe 10 years ago, maybe things have changed.

 

I absolutely will. But so far I have not found one. Even called in to parts department asking about it, and was informed that it wasn't available, and that the booster was a sealed unit and that seal wouldn't be a cause of what I was experiencing.

The ones I have seen are for other brands (Honda), and I am almost positive for other Toyota boosters, but it was a schematic picture, and when I clicked on the link to investigate which it would be for, it went nowhere.

So, this part is definitely made available in other applications.

Question for you Glamisman...how hard is it to take this seal out of our boosters? What keeps it in? Is it possible to try other seals? I'm ok with experimenting for the team if it's feasible.

 

They slide in and out easy and bottom out inside the forward shell of the booster.

 

Ok, so just pull it out towards the opening/MC, and when it goes back in, there's a material stop behind it... that will be observable once the one that's in there has been taken out?

 

Yes... it will make perfect sense once you see it.

 

I recently replaced the booster and mc on my truck with parts from NAPA. That seal was not included, makes me think it’s not totally necessary