Merc 3.7 Coolant in oil and blowing oil out breather

[dfleiby]

Hello All.

I have the famous Merc 3.7 Compression 150, 153, 155, 180 Yea All good. The issue is under load it is mixing coolant with the oil then blowing it out the beather vent. Inside the valve cover is a milk shake. I thought Blown head gasket, so I took the head off and can find no signs of where water was being forced in to coolant. The Head is new(remanufactured). I am not getting any water out the weep hole on the water pump (yes, it is NOT plugged). So what is going on, Blown inner sear on the water pump? Cracket Block? Where is the water getting into the oil and why is the crankcase pressuizing enought to blow oil out the breater? Im puzzled. Anybody seen coolant mixing with the oil? Teh motore is currently out of teh boat and he head is off. All Cylinders look great Cooland in oil toasted a lower rod bearing, thatats why I pulled the motor. but I need to figure out 100% how the coolant is gettting in the oil? Help Please

 

[rickryder]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Could be a bad intake manifold gasket. If you want to be sure the block is good send it to a machine shop to check for cracks...might as well have them replace the cam bearings and core plugs while they have it.

 

[dfleiby]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

How could teh intake gasket cause coolant in the oil. I am not aware of any coolant the goes thru that gasket.

 

[rickryder]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

My bad i was thinking of a v 6 engine....

I have seen bad reman heads too....

Don't the water passages in the head end against the intake? Could they be weaping into #1 or 4 cylinder? just throwin that out there....

 

[stonyloam]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Man that is a tough one. Aside from the head gasket and cam seals I can't think of anything, other than a cracked block, but there is no reason for that to happen. Maybe the weep hole is plugged internally. Pull the front cover and see. Please let us know when you find out the cause. Good luck.

 

[dfleiby]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Thanks for the input gang. Like I said, the motor is now out of the boat on rollers in the garage. Im gonna keep looking. Ya probably pull the front covers and have a look see at the seals. Im concered abou the block. Anybody know what is should cost to have the block checked?

 

[rickryder]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

I would break out your local phone book and call some machine shops.....it varies depending on where your located...

 

[stonyloam]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Just a thought, is there any oil in the coolant?

 

[dfleiby]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Actually, WOW! you coul be on to somthing. As part of the story, I colapsed a lifter as well. upon further inspection I see where Oil and coolant can definatly mix at the intake gasket and directly affet the lifter. When I have a chane I will inspect the surfaces and gaskets very closly aroud the #2 intake lifter area. This could be incouraging. Thank you!

 

[rickryder]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Keep us posted on what you find

 

[fmalott]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Hello All.

I have the famous Merc 3.7 Compression 150, 153, 155, 180 Yea All good. The issue is under load it is mixing coolant with the oil then blowing it out the beather vent. Inside the valve cover is a milk shake. I thought Blown head gasket, so I took the head off and can find no signs of where water was being forced in to coolant. The Head is new(remanufactured). I am not getting any water out the weep hole on the water pump (yes, it is NOT plugged). So what is going on, Blown inner sear on the water pump? Cracket Block? Where is the water getting into the oil and why is the crankcase pressuizing enought to blow oil out the breater? Im puzzled. Anybody seen coolant mixing with the oil? Teh motore is currently out of teh boat and he head is off. All Cylinders look great Cooland in oil toasted a lower rod bearing, thatats why I pulled the motor. but I need to figure out 100% how the coolant is gettting in the oil? Help Please

Everybody missed something look at his compression test the #4 cylinder is 30psi over should be 150 like the others, to me the head gasket is blown at the #4 cylinder it's one of the common things that happen to the 3.7 470 motors. cast iron head aluminum block. when i rebuilt my motor because of the #4 cylinder i could not see where thing where blown or mixing fluids. took the head to a machine shop and sure enough the head was warped. got it all fixed up good to go

 

[rickryder]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

If the head gasket was blown it would have a lower compression number wouldn't it? Unless he had coolant in the cylinder during the test...

 

[fmalott]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

If the head gasket was blown it would have a lower compression number wouldn't it? Unless he had coolant in the cylinder during the test...

exactly

 

[rickryder]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Well I would think the OP would have seen coolant blowing out the plug hole while he was cranking the motor during the other 3 cylinder tests....

 

[fmalott]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Well I would think the OP would have seen coolant blowing out the plug hole while he was cranking the motor during the other 3 cylinder tests....

when i did my test i had all the plugs out and nothing came out the hole. my head gasket was not really blown it was the head that was warped and the antifreeze was getting in the oil that way
well i guess we will see when the OP does more tests

 

[Jono69]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Regardless of the "age" of the head, that and the block need to be checked for a warped condition and/or cracks. Sounds to me like there may be more than one problem going on. My 170 crapped the bed only 2 months after a rebuild. I'd check and replace gaskets on the head and cooling system.

 

[dfleiby]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Hay gang, Rod bearing on #4 is shot. Going to ck rings on #4 tonight. I agree with Chief Petty Officer. Compression on #4 is wierd. I found minor evidence on the intake gasket where coolant may be getting into the oil there. Also I be checking the inner water pump seal to make sure coolant is not being pumped into the oil there.

 

[fmalott]

Re: Merc 3.7 Coolant in oil and blowing oil out breather

Hay gang, Rod bearing on #4 is shot. Going to ck rings on #4 tonight. I agree with Chief Petty Officer. Compression on #4 is wierd. I found minor evidence on the intake gasket where coolant may be getting into the oil there. Also I be checking the inner water pump seal to make sure coolant is not being pumped into the oil there.

sounds like a complete rebuild is in order GOODLUCK!