1989 Merc 5.7 - Water in oil, low comp in 3 cylinders

[qystan]

Engine is a 1989 Merc 5.7/Alpha Gen 1.<br /><br />Need pointers on where to look for the water entry. Could see some latte through the filler cap, not enough water to cream all the oil, waited for replacement head to do the job at one go.<br /><br />Was also having low compression on #2 (65psi), #6 (15psi) and #8 (5psi). Port head was changed mid last year, compression now are 100, 140, 100 and 135psi. <br /><br />Engine was started and warmed up. Did the air pressure test and confirmed exhaust valves sealing bad, no bubbles at the thermostat housing during the test. Would the exhaust valves be the water entry?<br /><br />Both exhaust manifolds are dry. Inlet ports and plugs are also dry.<br /><br />With Stbd head off, could see cream in galley area and at top of both cylinder heads. Do not see any water streaks in the galley area. <br /><br />Is it possible to do a magnaflux check of the galley area? Surface is pretty rough If yes, which area should I check, the bottom or sides or all? What about cleaning off the magnaflux developer - not into pulling engine and doing a ful dismantle. <br /><br />Inlet manifold gasket mating surfaces do not show water streak marks - would such be visible if there was a leak? Does water circulate in the rear portion of the inlet manifold or is it just around the thermostat housing area only?<br /><br />Are there other places I should look? Thanks.<br /><br />Oh, other than the above, engine ran fine

 

[trog100]

Re: 1989 Merc 5.7 - Water in oil, low comp in 3 cylinders

only three ways water can keep getting into cylinders really.. headgasket leaking between waterways and cylinders.. this would likely be limited to two adjacent cylinders at most.. <br /><br />freeze damage cracks in block or head..<br /><br />the first two apply to any engine not just boats..<br /><br />the other would be exhaust manifold corrosion.. this would also over time cause corrosion damage to valve seats and stem..<br /><br />trog100

 

[rodbolt]

Re: 1989 Merc 5.7 - Water in oil, low comp in 3 cylinders

hello<br /> do you have water in the cylinders or just in the oil? has the motor been run hot. its possible on the SBC to have a cracked exhaust seat that will allow water intrusion.<br /> I would not reccomend a magnafux unless an engine teardown is done. the "developer" in a magnaflux test is iron filings almost as fine as powder. there are some dye penatrants that can be used. but it may be time to pull the heads for inspection.<br /> the rear water ports on the heads are blocked off by the intake manifold. if the gasket is bad it can leak there as well.also check the underside of the manifold at the passages for the t-stat. if its freeze damage the normal spot on the block is just above the lifters.

 

[qystan]

Re: 1989 Merc 5.7 - Water in oil, low comp in 3 cylinders

Thanks guys.<br /><br />I don't get freeze damage over here. Lowest ever is 28C. Yes, I get to boat all year round , no break to recover from fuel dollars <br /><br />There was no water in the cylinders, makes this a bigger concern.<br /><br />1. Port cyl head was changed mid last year.<br />2. Had the flush hose fall off once and water reached 200F before shutdown. Water leak seem to have started after that, but unsure.<br />3. Had a look at the underside of the inlet manifold, do not see any crack/water stain marks. Are there water passages around the carb area of the manifold that I should consider removing the guard to take a look?<br />4. The inlet manifold bolts along the stbd edge was not as tight as I expected. thought I had torqued these. May be a possibility but do not see any water stain marks around the mating surfaces.<br />5. Will be replacing the stbd cyl head with a reman unit complete with valves and springs.<br />6. #6 piston is wet, looks like oil, will see if it dries.<br /><br />I should remove the port head as well and have that checked for flatness and replace the gasket for good measure.<br /><br />More suggestions on what other checks/insp I should do.

 

[rabidfish]

Re: 1989 Merc 5.7 - Water in oil, low comp in 3 cylinders

It's not really commomn but...<br /><br />If the gap of the engine cover is directly over the carb. There couold be water getting in the engine. It leaks through the flame arrestor bolt and in through the carb. <br /><br />I know it sounds weird, but it has happened.