Gaskets for Yanmar 3GM30F mixing elbow

[dmksails]

I have some confusion about the gaskets required for the mixing elbow on my Yanmar 3GM30F. When I took it apart it had 2 gaskets separated by a metal screen. This is what is shown on the one pic attached - except that that illustration is not for a 30F engine. The second doc shows what is listed for the 3GM30F - one single gasket. In addition, I ordered an elbow kit from HDI and it came with one gasket.

So, use one gasket as shown in the parts manual, or 2 and the metal screen as I took off?

[tkeithlu]

No one with direct knowledge of these two engines has picked up, so I'll take a shot at it. What you have called a "screen" they are calling a "spacer." Screen implies wire mesh to catch dead mice circulating in your raw water. Let's not go there. I can think of no good reason to "screen" here. "Spacer" on the other hand implies two parts won't fit together properly unless a gap between them is bridged. Is there anything interfering with the exhaust manifold mating with the mixing elbow, with nothing but a thin gasket between them? Does it stretch/kink the hose? Is there resistance to their fitting flat against each other? If that's the case, you need a spacer. You've got one. If not, proceed without the spacer/screen. If yes, you need a second gasket. If they are the same, get some gasket paper from your local auto parts store and cut out a new one.

Maybe learn the fine art of cutting gaskets. It will save you many times if you like digging into things like your exhaust system. Place the right kind (there are several basic types) of gasket paper over the flat of the part to be gasketed. Cut the paper by tapping the edges with the round end of a ball peen hammer. With a little practice,it's a lot faster and cheaper than getting stuck waiting for one to come in the mail.

Best wishes on your project.

[bobnlesley]

Our 3GM30F had just the rectangular gasket as shown on picture 72 - item 11 and never had a problem.
The one time I went to buy a new one they weren't 'on the shelf' and as I recall, were bloody expensive too, so I went into a nearby Auto Factors, bought an A4 sized sheet of suitable gasket material for a couple of quid and made one in about 3/4 hour; I've made another half-dozen for myself and others from the same bit of paper subsequently and there's still enough left for two or three more yet

[chris mac]

I had the same concern when I replaced mine. (1993 3gm30f)
The existing did not have the spacer and it was so damn tight and awkward to install, I went without it. It's been a year now and working perfectly

[Hesti]

Is the spacer made of plastic? In that case, it could be thermal insulation. Which might be needed for some operating conditions.

[Wotname]

AFAIK, there are two different possible manifolds which can be fitted to this engine. One has a rectangular end surface (i.e. 4 edges - call it type 1) and the other has a 5 edges (i.e. a sort of triangular section at the top yet squarish at the bottom - call it type 2). I don't know the proper name for this shape.

The rectangular elbow mating surface mates to the type 1 manifold with a single gasket.

However a spacer (item 13) is needed if the elbow is mated to the type 2 manifold, due to the different shapes and additional hole which exists in the type 2 manifold. When using this spacer, two gaskets are required - one on either side of the spacer. You will note that one gasket is rectangular (4 edges) while the other gasket has 5 edges.

[Wotname]

Originally Posted by tkeithlu

No one with direct knowledge of these two engines has picked up, so I'll take a shot at it. What you have called a "screen" they are calling a "spacer." Screen implies wire mesh to catch dead mice circulating in your raw water. Let's not go there. I can think of no good reason to "screen" here. "Spacer" on the other hand implies two parts won't fit together properly unless a gap between them is bridged. Is there anything interfering with the exhaust manifold mating with the mixing elbow, with nothing but a thin gasket between them? Does it stretch/kink the hose? Is there resistance to their fitting flat against each other? If that's the case, you need a spacer. You've got one. If not, proceed without the spacer/screen. If yes, you need a second gasket. If they are the same, get some gasket paper from your local auto parts store and cut out a new one.

Maybe learn the fine art of cutting gaskets. It will save you many times if you like digging into things like your exhaust system. Place the right kind (there are several basic types) of gasket paper over the flat of the part to be gasketed. Cut the paper by tapping the edges with the round end of a ball peen hammer. With a little practice,it's a lot faster and cheaper than getting stuck waiting for one to come in the mail.

Best wishes on your project.

While it is called a spacer, it would be better described as an 'adapter' as in this application, the intent is to accommodate two different footprints rather than bridge a gap.

When the footprint of the elbow and manifold is identical, the spacer is not required.

When the footprints are different, the spacer/adapter is required.

[roverhi]

The heat exchanger/manifold to exhaust elbow gets hot engine exhaust gases and needs a heat resistant gasket. I'd be worried about a home made paper gasket burning up from the heat. The Yanmar gasket is a metal sandwich with some form of heat resistant material in between to compensate for any variables in the mating surface. My Yanmars use the rectangular #11/14 gasket to mate to the exhaust elbow.

[Glasshopper]

I'm having trouble zooming in on your pics on my phone.
BUT on my volvo exhast elbow, the gasket is between exh manifold and the elbow/riser (the latter is seawater cooled).
Instead of a gasket I've been using non-acetal (neutral cure) silicone, rated for 140 degC constant. No problems for 10 years. Regards, Bert.

[jamhass]

No idea if this is relevant to this discussion, but

Some of the cars I've owned have multi-layer exhaust manifold gaskets. One I recall had 2 thin metal sheets sandwiching a wire-reinforced fibrous material (I'm old enough for it to have been asbestos.)