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Copper Exhaust Gaskets 2QM20 Yanmar and oil pressure questions.

2K views 8 replies 3 participants last post by  Markwesti 
#1 ·
I had my exhaust manifold pressure tested and put new copper-cardboard-copper,(for want of proper name) gaskets on and now cannot stop them from leaking. I am not using any sealant and cleaned and polished the surfaces before putting them on and tightened them to proper torque, I think. Is there a special way to install copper gaskets?
When first starting my engine the oil pressure will go up to about 20 psi and then slowly in 10 minutes or so get up to 35 or 40. Is this normal.
Thanks for any input.
 
#2 ·
Not sure if your 2QM20 manifold arrangement is the same as my 2QM15. My manifold has three gaskets...one at the discharge from engine to manifold, one on the fwd end of the manifold on what is essentially a blanking plate (to which the engine mounted fuel filter mounts), one on the after end for an exhaust flange that mates to the exhaust riser...and a small spacer "gasket" whose purpose is to level the manifold at the engine attachment...which uses six studs, only four of which are used for the exhaust outlet to the manifold (which is gasketed with a copper sandwich gasket). Without the spacer, the manifold will not set parallel to the mating surface at the gasket. Is that spacer in place?

You don't mention if that is the gasket that is leaking. In any case, if the gasket surfaces are clean and flat, and the gaskets are good, and the torque is right, and the fasteners were torqued in the proper sequence (this is important), the gaskets should not leak.
 
#3 ·
2QM15 also , in the past I have used Copper Coat Silicone on the exhaust flange that bolts to the manifold . But if you have a warp I doubt it would help , to check for warp get a flat plate and some 80 grit sand paper and hone down the two surfaces , put some ink on there and hone some more and check for low spots . For oil pressure what you are saying is kinda weird , usually it will start out high and then get lower . I suspect a sending unit . For the 2QM15 when up to temp it should be 35 #s' at full throttle and 3-4 #s' at idle .
 
#4 ·
I have the "spacer" on where the exhaust manifold bolts to the engine. It is the "Riser" and "Blank" end where the fuel filter bolts on. The Copper Clad gaskets. Do you happen to know the torque specs and sequence? There are only the four bolts on the Riser (fore) and three on the Blank (aft) gaskets. I could probably use Permatex but would rather be able to make it seal without sealant. Unless of course that is what is called for.
Thank you for the reply.
 
#5 ·
Thanks for the reply. I put on a new pressure gauge, mechanical, and it was the same. On startup it goes to 20psi and then after it is warm it goes up to 35-40 psi. At idle it goes down to about 30 I think. Although I did at one time put a NAPA filter on it and it went to 40 on startup! Scared me so I went back to OEM filter.
 
#6 ·
If you don't already have the service manual for your engine, Froggy, it's available for download on line, for free. No specific torque value for the manifold flange nuts and bolts are listed, but the general spec for an M8, which I think these are, is 2.4-2.9 kg-m, which is about 17-21 ft-lbs.

The torque sequence for the four bolt flange is to snug everything up, then torque in a cross pattern...eg, top right-bottom left-top left-bottom right. I usually torque each to about 50 percent of rated on the first go around, then torque to spec on the second. The purpose is to keep the flange face flat as it is torqued. On a three bolt flange, no sequence is needed...just go round the flange sequentially tightening in the same fashion. Snug, then half spec, then to spec...or something similar.

Good luck.
 
#7 ·
And I wouldn't use Permatex except as a very last resort. Those flanges are small and pretty thick, not prone to warping, and if the surfaces aren't pitted or corroded, the gaskets should seal them.
 
#9 ·
On the 2QM15 there is a shim to regulate oil pressure , it is in the tube that the oil filter threads onto . But that is not your problem and to tell you the truth I don't think you have a oil pressure problem . Also you are using a mechanical gauge , and that is I think the most accurate but I would switch back to electric . It is also really weird that the NAPA oil filter would give you more pressure at start up I would stick with OEM filter . Something is going on with your oil pressure but I don't think it is a big deal , in my 2QM15 manual it talks only about low oil pressure , it says low oil press. is caused by worn out stuff like the crank shaft and rocker shaft but they don't say anything about the oil pump being worn out and that is the hart of the little beast . Possibly that is a cause , but still low press. then high press .? It doesn't make sense , at least to me . Our 2QM15 starts out high 35#s'@ 900rpm not in gear just warm up and 15#s'@ idle cold , and ohboy at full throttle after say 4-5 hrs. motor sail 2,650 rpm we are lucky to get 18#s' and we pray the low press oil light does not come on at idle . I use Delo 40 and a half can of Lucas .
 
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