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Exhaust Leak -- scenarios?

Okay, I donned my white lab coat and, with the help of Inge, my sexy lab assistant, I tried the hand-over-the-end-of-the-tailpipe test to check for an exhaust leak. Burned my hand. While Inge cooed over my owie and offered to make me feel better by taking my mind off it, I waited for my

71 bus to cool. Once cool, I tried it again, and the bus kept running. So I have an exhaust leak.

A few days ago I reconnected one of the heater control cables and hooked up new ducts from the cooling shroud to heater boxes. With the red lever hauled to the "open" position, I smell exhaust in what should be warm air. This with the bus moving and not moving.

Question: are there any scenarios where exhaust fumes can get into the heated air channel that does *not* involve leaks in the heater boxes?

In other words, should I order new heater boxes now?

Reply to
Mike Rocket J. Squirrel Elliot
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Hi.New heater boxs for that engine are not too expensive.For your peace of mind and your familys safety your bus deserves them(hows that for rationalising).Really,Brazilion(affordable)boxs should do the job for you in SDiego.Isee them on Samba alot.Steve

Reply to
Ilambert

Well, I'm keeping the heater levers shut until I sort this out. So -- am I correct in assuming that the only likely way exhaust fumes can get into the heater air it through a leaky heater box?

This occurs with the bus moving and with it not moving, and I do have an exhaust leak (will attempt to locate precisely on Friday).

Reply to
Mike Rocket J. Squirrel Elliot

...nope

Reply to
Gary Tateosian

Hi.Unfortunatly there are lots of other places for leaks.The flanges at the head/manifold ,the donuts between heater boxs and the muffler,even the muffler itself.The square shape of the Bus sucks a certain amount of air forward due to the vacuum it creates so any exhaust leaks go with it.Old heater boxs do leak and because of their construction the leak can't be seen.If nothing seems obvious(gaskets,donuts)my money would be on internal leaks in the exchanger(s).Yours look old and worn(no offence).Also there used to be a "repair kit"for the pipe where it connects to the muffler.That rearmost several inches wears,rusts,is generally buggered up and doesn't seal tite.Haven't seen it in years tho(maybe J.C.Whitney)?Steve

Reply to
Ilambert

Goody. I get to learn more. Here's my understanding.

Cool outside air gets sucked into the cooling shroud by the fan, from some source that I can't quite identify from the Bentley's manual.

Meanwhile, cool air gets drawn or forced into the air scoops behind the rear passenger windows and downward to some destination I can't quite figure out. Maybe these two items -- the intake scoops and the inlet(s) to the shroud are connected?

Is this a closed connected? That is, is inlet to the shroud open to the world or meant to be connected to the scoops? If closed, then presumably exhaust can't get in that way. But probably not. If the fan gets its air from wherever, then my leaky exhaust manifold could be feeding exhaust right into the intake opening of the shroud. As Eduardo said in an earlier thread, "Turned out to be a leaky heaterbox to muffler joint that got sucked back into the fan..."

Moving on, the fan forces air out of the shroud through the two hoses to the heater boxes, which route the air around the hot exhaust manifolds. If there is a hole in the exhaust manifolds inside the boxes, that's another possible source of leakage.

Have I covered the bases?

Reply to
Mike Rocket J. Squirrel Elliot

I had two leaky places to fix before the problem went away... one was the leak itself (the muffler to heater box conection)... but the other place fumes were getting sucked in was the koint between the outer air jacket and the inner tube of the heater box.

As far as I could infer, the fan pushes air into the heater box, but some how the air flow produces a small amount of vacumm in that are (the outer jacket to inner tube joint) that makes fumes get sucked in...

Maybe is was something that just occurs with cheab brazilian heater boxes, but to be sure, I now got mi german boxes out of the car and welded them in that joint...

Maybe I should post a picture...

Reply to
Eduardo Kaftanski

Take off the muffler take off the heater cables take off the heater boxes

now with them off you can test them. Its very sientifcic and very technical.... Plug one end with you hand and then blow into the other end...(yes you'll get a round black mark around your mouth...please post a picture). If you cant blow air then no leak.

Tim

Reply to
Tim

Oh sure. I get it. Get the new guy to do something silly and then make fun of him. Well, I'm not falling for this one. I'll have Inge, my attractive lab assistant, blow the pipe. Then charge you doofuses good money for a copy of the picture.

Reply to
Mike Rocket J. Squirrel Elliot

ROTFLMAO!!!

:D

BTW it's not necessary to remove the muffler first.

Jan

Reply to
Jan Andersson

On a BUs you don't need to pull the muffler to get the boxes off. After everything is loose just push them forward and they will come off. Other than that Tim's idea for checkign the internals is great and should isolate the problem quick enough as to whether its your heater boxes.

--Dan E

Reply to
Braukuche

on a brazilian bug, you dont need to either...

Reply to
Eduardo Kaftanski

Reply to
Ilambert

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