found vacuum leak??? Ideas???

[spstan]

I switched from thinking the intermittent rough idle on my 75 New Yorker (440 engine) was due to carburetor problems to thinking it was due to vacuum problems. I found 2 possible sources of vacuum leaks. The first pictures show the vacuum tree at the back of the engine where the power brake vacuum line is attached. To the rear of the brake vacuum line is a small vacuum nozzle (at the tip of the pink pointer) with no hose attached. I have no idea what this vacuum nozzle is for or where it goes. If no one else on this board knows I'll probably just cap it off.

The second possible vacuum leak may be from a hose that emerges from the fire wall and again I don't know where it goes (it may be the vacuum pull off for the emergency brake). I found it just lying on the back of the manifold. One picture shows it at the tip of the pink wire and one shows it under a red wire that crosses over it.

Can anyone tell me what these vacuum sources are and where they go? Thanks Paul

 

[CBODY67]

Part of diagnosis is "try and see", so cap the metal tap on the power brake vacuum tree and plug the other hose. Pre-made vac caps can be found on the "HELP!" racks at auto supplies. Usually in a multi-size cap package. For vacuum lines, golf tees or similar can work.

The other thing is "How long have they been uncapped and why/how?"

CBODY67

 

[Sixpactogo]

The hose going thru the fire wall is more than likely for your heater controls. It looks to me that it should hook up to the nozzle that is uncapped.

 

[413]

Do your heater controls work as they should and the hot/cold selector.

What doesn't work?

Yes put that hose on the tree and see what it does.

 

[spstan]

Part of diagnosis is "try and see", so cap the metal tap on the power brake vacuum tree and plug the other hose. Pre-made vac caps can be found on the "HELP!" racks at auto supplies. Usually in a multi-size cap package. For vacuum lines, golf tees or similar can work.

The other thing is "How long have they been uncapped and why/how?"

CBODY67

CB; I'll cap the small nozzle on the vacuum tree but plugging the hose doesn't make sense cause it is going to the vacuum source not coming from the vacuum source. I can't see where the vacuum source is for that hose. Paul

 

[spstan]

The hose going thru the fire wall is more than likely for your heater controls. It looks to me that it should hook up to the nozzle that is uncapped.

Six; I was hoping that was the case but the small nozzle and the hose are of vary different diameters. Paul

 

[spstan]

Do your heater controls work as they should and the hot/cold selector.

What doesn't work?

Yes put that hose on the tree and see what it does.

six; the hose and the nozzle on the tree are of 2 very different sizes. Paul

 

[spstan]

Part of diagnosis is "try and see", so cap the metal tap on the power brake vacuum tree and plug the other hose. Pre-made vac caps can be found on the "HELP!" racks at auto supplies. Usually in a multi-size cap package. For vacuum lines, golf tees or similar can work.

The other thing is "How long have they been uncapped and why/how?"

CBODY67

CB; I don't know how long they've been unplugged. My next step is to put the car away for the winter (this stuff will make you crazy if you don't step away) and then in the spring try the propane gas method they posted on you tube. Anyone successfully use propane gas to find vacuum leak? Paul

 

[CBODY67]

The ONLY thing I would use Propane gas for is the old Propane gas-assist method of adjusting idle mixtures, in the later 1970s.

Propane gas (in u8nexpected places) + Spark (at unexpected time) = BOOM!

CBODY67

 

[Big_John]

six; the hose and the nozzle on the tree are of 2 very different sizes. Paul

That hose may have been just stuck on there by some half assed mechanic in the car's past. It finally came loose.

What you NEED to do is look through your FSM at the emissions section for some of the vacuum hose routing. Then the HVAC section for other hose routings. Maybe the fuel section too.

Sometimes there is even a sticker under the hood of hose routings.

 

[CBODY67]

Vac hose routing graphics were ONE of the best things the OEMs did, back then. Quite colorful, too. BUT time and heat and such were their demise, unfortunately. MANY were reproduced in the FSM.

What I discovered was that if one knew how the emissions item worked, when it worked (hot or cold coolant, or when it was not supposed to work), and could see the vac hose sizes on the Thermal Vacuum Switch (as the same size hose would be used on the switch nipple as on the item that hose went to), THEN . . . it could be figured out what when where. But not everybody could figure this out, after the vac hose map went away.

A different world back then. Ford probably did not use such maps and the Oldsmobile V-8 maps were "spaghetti", as their motors were literally covered in a layer of vac hoses, by observation.

Thanks, @Big_John for mentioning the vac hose routing graphics that were EVERY car built back then.

GM used to print these hose maps in the factory service literature, but later stopped doing that. Notifying everybody in "service" to use the sticker/map that was on the car (usually on the top of the core support) as the "factory documentation" of what was on the particular vehicle the sticker was stuck onto. Which made things ever worse after the tag might be deteriorated and "washed off" by a high-pressure car wash. So, I ended up calling GM Engineering operatives to get them to fax me a copy (low-res black and white) copy of the original colored label. Which they would pull from their files. After a few years, the requests to me stopped. Not sure if ALLDATA had begun supplying them or not?

CBODY67

 

[Sixpactogo]

six; the hose and the nozzle on the tree are of 2 very different sizes. Paul

How about the larger barb on the vacuum Tree that has a cap on it? Swap that hose onto that barb and find a small plug for that smaller barb. That loose vacuum hose has to be for something. Either the heater controls or maybe light switch if you have vacuum headlight doors or a vacuum gauge.
Also, it appears that hose has some sort of adaptor on the end. Did it have a reducer or something that mated the hose to that small barb?
Does your heater controls work?

 

[WissaMan]

This is the diagram from my 77 manual showing the vacuum parking brake release hoses

 

[spstan]

How about the larger barb on the vacuum Tree that has a cap on it? Swap that hose onto that barb and find a small plug for that smaller barb. That loose vacuum hose has to be for something. Either the heater controls or maybe light switch if you have vacuum headlight doors or a vacuum gauge.
Also, it appears that hose has some sort of adaptor on the end. Did it have a reducer or something that mated the hose to that small barb?
Does your heater controls work?

You what SIX? You may be right after all. That small nozzle had about an inch of hose on the end of it and I initially thought nothing of it figuring it was just the remnant of a broken piece of hose. BUT after further inspection the one inch remnant (and I can supply a picture if anyone is that interested) has a narrow end that attaches to the nozzle and then it fattens out at the opposite end. So I'm wondering if that fat end fits INSIDE the end of the hose that was loose. I'll try piecing them together and see what happens. As you say the loose hose has to attach to something. Paul

 

[spstan]

You what SIX? You may be right after all. That small nozzle had about an inch of hose on the end of it and I initially thought nothing of it figuring it was just the remnant of a broken piece of hose. BUT after further inspection the one inch remnant (and I can supply a picture if anyone is that interested) has a narrow end that attaches to the nozzle and then it fattens out at the opposite end. So I'm wondering if that fat end fits INSIDE the end of the hose that was loose. I'll try piecing them together and see what happens. As you say the loose hose has to attach to something. Paul

first sentence should have read "you know what Six? " Paul