Remember how I was bitching and moaning about this vacuum issue that I can't seem to solve? And then I removed my WUR cleaned it and opened up an entire can of very slimey worms. Well I still have the vacuum leak and it's very funny one because now my car starts right up in the morning (now that the WUR is clean and my mixture is set correctly again and the water was removed from fuel). The idle is solid at first and then will starting hunting around but then (after a brake application or two) the idle shoots up to 1900 and stays there solid!

I have always complained that the brake pedal had too much travel and now I'm starting to think that has something to do with the vacuum issue. I was at a traffic light this morning, I was ideling ok, all the sudden I could feel the pressure drop in the brake pedal the idle shot up to 1900. I was looking for a vac line in and around the booster but I'm not seeing anything.

Am I going in the right direction here?

Rob

There is a large vacuum line from the brake booster to the intake manifold. it is probably still original, probably braided cloth, with plastic connector. about 3/4" diameter.
your problem sounds really wierd, though. i dont know what could be wrong.

The vacuum line from the brake booster to the manifold has a check valve. It might be defective If you can change it out...hell change the whole line and see if that improves it. Your brake booster could be going on the fritz too. Does your idle go up a lot when you pump your brakes? According to Layne that means the booster is on the way out. I have that problem!
Keep us posted as to what you find out.
Good luck on solving the prob.

Many thanks for the feedback. I know which line and connector you're talking about - thanks for letting me know what they do.

It was Layne's comment about the booster that started me thinking in the first place. To be clear, is the booster up against the firewall behind the master?

When I press on the pedal sometimes there is a 3-400 rpm jump but this morning the pedal lost pressure the rpm's shot right up to 1900rpm. I think this is the first time I really noticed it happening. Before I would be driving and then stop the car and the idle would be up at 1900rpm. This was the first time it's happened when the car was stationary with my foot on the pedal. TG for parts cars.

Rob

It does sound like a booster problem. The check valve is of no consequence, I didn't even bother to put one in.

It does sound like a booster problem. The check valve is of no consequence, I didn't even bother to put one in.

Hey Layne,

Can you confirm the location of the booster?

Thanks,
Rob

http://www.amazon.com/BMW-320i-Owners-Workshop-Manual/dp/1850100721

I say brake booster as well. PITA to change, but if it is original, probably time for one.

http://www.amazon.com/BMW-320i-Owners-Workshop-Manual/dp/1850100721

Ha Ha - I ordered one just over 3 weeks ago and it has yet to arrive

I say brake booster as well. PITA to change, but if it is original, probably time for one.

Thanks. So the booster is the large black cylinder - those are expensive....... I hope the two parts cars I have access to have good ones.

Rob

Yeah, new is like $400. But they usually last almost forever.

Except in cases like this lol.

It's rare that they fail but they do. Sometimes they suck brake fluid into the intake even. Check the brake fluid level. I have heard of this happening more to old Brit cars on triumph boards..

Not going to do much good, if it's shot it's shot!

amazing, I just had to fill the brake fluid level, very low, just seemed to disappear and the car's been chasing idle recently. If I understand here, when/if the brake booster goes bad, in can suck brake fluid into the intake.?

is the intake controlling pressure here? whats that connection

No, thats a master cylinder failure that can do that. But the brake fluid will destroy the booster too. The booster has to get nearly half full before it starts spilling into the footwell or the intake so you should notice alot of missing fluid.

I have not had time to take a close look yet but is this an fairly straight forward undo bolts remove and install the new one operation or do brake lines have to be bled and and and?

I hate to say it but I don't have $400 laying around for a new one. I think I might take one from one of my donor cars and try that. It's not the best option but it would be nearly free - is this a really bad move?

Rob

Used is perfectly fine. They usually last a long time. I'm not sure if you'll have to take the lines off the master cylinder, maybe you can squeze it out without. No big deal if you do have to take them off though.

You might go one step further and either get a rebuild kit for your brake master, or use one of the donor brake masters that you have. Just in case your issue is two-fold; booster and master cylinder.

Why not just get new for both?

:confused um, because they rarely go bad and a new one costs about $650 from a bmw supplier...

My dad's '73 2002 still has the original booster, so does my car.

My idle surges up 3-400rpm when i pump the brakes too, i always suspected the check valve. Been too lazy to diag it since the car runs perfect otherwise

Tomorrows the day - I'll be harvesting the booster and the master and hopefully will complete the work on the weekend.

Thanks for all the advice and I'll let everyone know if this cures the issue.

Rob

It's rare that they fail but they do. Sometimes they suck brake fluid into the intake even. Check the brake fluid level. I have heard of this happening more to old Brit cars on triumph boards..

mine was like this when i first brought it, it had a "blown head gaskit" turned out to be the master cyl, cars dont like running on brake fluid....made the car very cheap though:buttrock

My idle surges up 3-400rpm when i pump the brakes too, i always suspected the check valve. Been too lazy to diag it since the car runs perfect otherwise

Thats totally normal.

The check valve is irrelevant to normal operation. Its only function is to allow you to have powered brakes for 2 or 3 pumps after the engine dies.

Well I surprised myself and was able to make it over to the parts car late this afternoon. I was able to remove the master and the booster - good times :rolleyes. What a bitchy little item that was to remove but I will say though; every single nut I had to remove (even the ones on the inside of the fender holding the bracket in place) came off like a champ.

The brake lines were easy to remove from the master although I was totally PO'd when I was trying to remove the line from the side of the fluid reservoir and I broke the plastic nipple. I have a feeling I have rendered that master cylinder useless - lucky I don't need it.

There is an easy to remove clip and pin on the brake pedal and then your ready to "extract"; that's the really fun part. Because the rod that goes through the firewall to the brake pedal is so long you need to pull the booster fairly far forward in the engine bay but you really don't have that much room. I found the biggest problem was the black metal tube with a sensor attached under the throttle body (and what is that cool little white box with the two wires attached anyway?)

The trick to removing the booster is that you can pull it far enough out that you can see an adjuster nut on the end and a copper "Y" connector for the brake pedal. Take 16mm and 17mm wrenches and loosen the nut - the "Y" comes off and then you have just enough space to reef the booster out because the rod is that much shorter.

If I could have removed the starter (and I need it) I think that would have allowed for more room for booster removal. I did get the two bolts out that hold the starter in and I could move the starter back and forth but there are thick wiring harnesses in the way and I was not prepared to cut them.

ANYWAY - the booster I removed might actually be a replacement booster and I'm hoping this is the ticket to success. I won't be able to get at the install next week.

Rob

Sounded like fun.
By the way I only suggested that you get new for both because I have learn that it doesn't always to be cheap. Something breaks, works but then breaks later when its like 2am and you don't have the cash for a tow, and things like this. So for certain things (the more pain n d az to do - it's new) I just buy a new part, saves time and headaches.

Well this has been a "discouraging" two days :rolleyes. Booster changes are not fun.

Q: If you suspect that your booster is creating a vacuum issue could you not remove the vacuum line coming from the booster to the manifold and then plug the open hole on the manifold (just for testing purposes), start the engine and have the engine idle as if there was no vacuum leak??

I set to work on my booster. I removed the brake lines from the master, unbolted the master from the booster, undid the booster pin from the brake pedal, undid the bracket from the fender and removed the master, some other various odds and ends. When I pulled the master out of the booster there was a popping sound which I think is normal. I found a rubber o-ring in the booster which is used to seal the master to the booster. I think it may have go sucked into the booster when I separated the two pieces.

I tried everything to get the booster out of the engine bay - but I couldn't. I don't want to sound like a chicken sh** but I was not up for removing the manifold because I've never done this before and I didn't want to start something I couldn't finish.

The alternative was to unbolt the pedal support (that's what I'm calling it) on the firewall and pull it back but this looked like it might be a bit of a Pandora's Box as well. The overall problem of course if the rod that goes from the booster to the brake pedal throuth the firewall.

Am I missing something here? Is there an easier way? And no, my stupid Haynes manual has NOT arrived from Amazon yet.

Experts, get on your thinking caps.

Rob

Q: If you suspect that your booster is creating a vacuum issue could you not remove the vacuum line coming from the booster to the manifold and then plug the open hole on the manifold (just for testing purposes), start the engine and have the engine idle as if there was no vacuum leak??

Yes, absolutely.

I never tried to remove one, but it looks like it would just slip out, oh well.

Wish I could be of some help, but I have never removed one of these before. But this is exactly why this would be a NEW replacement for me.

Wish I could be of some help, but I have never removed one of these before. But this is exactly why this would be a NEW replacement for me.

New or used is irrelavant, you still have to remove the problem booster. I'm really hoping that someone out there has done this and can provide some insight. The booster cylinder is so big that it will only go so far forward and the rod going through the firewall is not far enough forward for complete removal - if that makes any sense at all......

It makes sense, I have changed out mine. You need to take the black support rod loose from the intake manifold. Just take the nuts off and let it swing around as far as it will go on its own, you do not need to take anything else loose you just need that extra little bit of room for the booster to go forward. Once the support pole is loose guide the booster toward the front of the car and rotate it until the booster rod will clear the housing and lift it out. I assume you have the master cylinder off as well.

what you talking about:confused boostersare easy this side of the pond:stickoutt

It makes sense, I have changed out mine. You need to take the black support rod loose from the intake manifold. Just take the nuts off and let it swing around as far as it will go on its own, you do not need to take anything else loose you just need that extra little bit of room for the booster to go forward. Once the support pole is loose guide the booster toward the front of the car and rotate it until the booster rod will clear the housing and lift it out. I assume you have the master cylinder off as well.

That's exactly the information that I was looking for. I'll go at it again soon.

Many thanks,
Rob

I know I was going down the booster road but I shifted gears a bit. I removed the vacuum line from the manifold and it made no difference to my high idle issue - none. So I'm still looking. I know some will heavily disagree but I'm seriously starting to think it's not a vacuum issue simply because it seems like the idle shoots up to exactly the same rpm every time the engine gets to a certain temp and then it stays there and is very consistent. Initially when I start the car the high idle is normal then it comes down to about 1100rpm which is where I have the idle set but after a few minutes and engine warming time, away the idle goes up to about 1800rpm and it stays there.


I did have another problem with my brakes and that was that the brake pedal had way to much travel. I bought a new master, did a good bench bleed, installed and bled the lines and my brakes are golden - at least I'm getting somewhere.

Rob

So good on ya, mate! At least you have the brake problem solved. Fluid leaks out of the master cyl into/under your carpet, so that is probably where your fluid went if that happened. On your idle, you could have a cracked intake boot where you cant see it. It's soo hard to say with out my own eyes on the car..If I were there I would go through the base settings, throttle cable, throttle plate, curb idle. then try and set mixture. Idle should be around 1K at most.

Have you messed with your idle screw much? It can get way out of wack after lots of tune ups where they turn the idle up at the end. Once you know that setting is correct, then you can play with fuel, assuming that your timing is good.

John

So good on ya, mate! At least you have the brake problem solved. Fluid leaks out of the master cyl into/under your carpet, so that is probably where your fluid went if that happened. On your idle, you could have a cracked intake boot where you cant see it. It's soo hard to say with out my own eyes on the car..If I were there I would go through the base settings, throttle cable, throttle plate, curb idle. then try and set mixture. Idle should be around 1K at most.

Have you messed with your idle screw much? It can get way out of wack after lots of tune ups where they turn the idle up at the end. Once you know that setting is correct, then you can play with fuel, assuming that your timing is good.

John

I inspected the intake boot again the other day. I really cannot see any cracks in the in the boot at all. Having said that though - I haven't taken it out the rubber is very stiff - what is the trick to getting that boot out of there?

Also and more importantly, if this was a vacuum leak I wouldn't think that I would ever have a normal idle and I do have normal idle for a short time just after I start the engine - that's what has me the most concerned.
Rob

Never mind.

I inspected the intake boot again the other day. I really cannot see any cracks in the in the boot at all. Having said that though - I haven't taken it out the rubber is very stiff - what is the trick to getting that boot out of there?

Also and more importantly, if this was a vacuum leak I wouldn't think that I would ever have a normal idle and I do have normal idle for a short time just after I start the engine - that's what has me the most concerned.
Rob

Getting the boot back on is the hardest part! I leave mine in the sun if it's summer so it's flexable. Heat it up.

I am at a loss as to what is causing this. Swap the WUR? I cant remember reading if you did or not, too lazy to check:rolleyes If you don't have a fuel pressure gauge for Kjet, you have to play the remove and replace game with your parts bimmer.

Huh, so a bad master cylinder might explain why my brake pressure sucks and the carpet on the driver's side of the car was soaked and nasty. Time to find a used one :)

Huh, so a bad master cylinder might explain why my brake pressure sucks and the carpet on the driver's side of the car was soaked and nasty. Time to find a used one :)

Uh, I would say the tell tale signs are there. I'm all about budget but I would not bother looking for a used master. I got mine for under a hundred (re-man) plus the core charge. It made all the difference in world.

So I get a PM from AltBimmerKang this morning to give him a call in Georgia. I gave him a call and we had a great chat about the vacuum issue I was having. As per my description he had the same problem.

I made some notes and went to work. I went and bought some vacuum system plugs for 3 bucks, headed for my shop and did the following:

1. There is a large vacuum line between the valve cover and the manifold. On this line there is a t-connector w/ a small vacuum line going from the middle of the joiner to the underside of the manifold (drivers side). There are two vacuum connections on that side of the manifold. One was already capped (and now they both are). I then capped the open end on the t-connector and started the engine.

2. The engine was now running much better. After about 5 minutes the idle started to hunt up and down in the 700 to 1200 range. I already new that my mixture was too rich as per all the dicking around I've done in the last few weeks trying to figure this problem out (my fuel economy has not been good). I took my 3mm hex tool and leaned the mixture out little by little and what do you know - no more hunting - beautiful smooth idle.

3. Now running much better and warmed up, my idle was at about 1100rpm. I adjusted it to 900.

My engine is purring like a kitten!!! I am so pleased. What a difference a 45 minute phone call made, we had a great chat. It was great just to talk to another 320 owner!

Many thanks to all who made a contribution to this thread.

Rob

This is what I was going to say,.....

Just a guess but it could be one many starting with Cold Start Injecton Valve, or Thermo Time Switch. But don't rule out vacuum leaks there are so many things that could leak on older vehicles.

But then noticed that what I was going to respond to was old (my email) but glad to see you got it fixed, and it still turned out to be a vacuum leak after all.

Where is the hex idle adjusting screw?

I haven't ever touched mine yet so I have no idea.