The recent postings on tips for buying a used RV reminded me of a method
I saw Chuck at OASI use to answer my question if the Transmode I was
evaluating for purchase had an exhaust leak.
I was new to GMC's and the 455 but had heard the stories about their
propensity to develop manifold leaks. The engine sounded good to me as
it idled in park---there was no exhaust roar coming from the engine
compartment but I thought I heard a slight difference in sound coming
from one side. Chuck wasn't sure if there was a small leak so he took a
3 foot long piece of scrap garden hose and, using it like a stethescope,
held one end to his ear while moving the other end back and forth along
each exhaust manifold holding the free end an inch or two off the hot
surface.
Using this method Chuck quickly diagnosed that there was a small leak
developing at one of the cyliners and let me listen. The hose
concentrated the almost imprectible puffing sound and the leak became
very obvious.
I used the same technique when looking at other coaches and found some
with leaks and some without. I finally ended up buying the Transmode
but the manifold gaskets were replaced first by the seller. A couple of
thousand miles later the leak was back and I had to get the warp removed
from the manifolds by having them surfaced at the machine shop.
However, I still use the hose method to routinely check for leaks now
knowing that way I'll increase my chances of finding and fixing a small
one before it gets out of hand and exhaust erosion harms the heads.
Phil Stewart
'76 Transmode
I saw Chuck at OASI use to answer my question if the Transmode I was
evaluating for purchase had an exhaust leak.
I was new to GMC's and the 455 but had heard the stories about their
propensity to develop manifold leaks. The engine sounded good to me as
it idled in park---there was no exhaust roar coming from the engine
compartment but I thought I heard a slight difference in sound coming
from one side. Chuck wasn't sure if there was a small leak so he took a
3 foot long piece of scrap garden hose and, using it like a stethescope,
held one end to his ear while moving the other end back and forth along
each exhaust manifold holding the free end an inch or two off the hot
surface.
Using this method Chuck quickly diagnosed that there was a small leak
developing at one of the cyliners and let me listen. The hose
concentrated the almost imprectible puffing sound and the leak became
very obvious.
I used the same technique when looking at other coaches and found some
with leaks and some without. I finally ended up buying the Transmode
but the manifold gaskets were replaced first by the seller. A couple of
thousand miles later the leak was back and I had to get the warp removed
from the manifolds by having them surfaced at the machine shop.
However, I still use the hose method to routinely check for leaks now
knowing that way I'll increase my chances of finding and fixing a small
one before it gets out of hand and exhaust erosion harms the heads.
Phil Stewart
'76 Transmode
