Water in the oil - should I replace head gasket

[seapro17]

Greetings,

I recently bought a 1985 Chapparal with a Mercruiser MCM 260 (Chevy 350). The engine had been recently "rebuilt". It supposedly had about 10 hours on the rebuild. It ran fine, but I noticed steam in the through-hull exhaust. I've got another boat that's a twin-screw 350 with through-hull exhaust and have never seen steam, but preferring to be in a state of denial, I thought it might be normal. Then I noticed oil puddling on top of the manifold. I couldn't tell if it was coming from the valve cover breather hose or wicking up the intake manifold bolts. Then, I started getting water in the oil. Now I seriously doubt the water in the oil is from a crack anywhere, because I ran it for probably 15 hours and I never got water. So I thought it could be the exhaust manifold and risers. So I replaced the starboard manifold and riser (port side is new, the guy said he didn't winterize right and it cracked and had to be replaced, this was shortly after the rebuild). I replaced all exhaust manifold and riser gaskets on both sides. Didn't change a thing, still see steam, still see oil puddling, still getting water in the oil.

So then after a bit of research, I found that on the older 350s, you have to put a thread sealant on the intake manifold gaskets, because the bolts go through the oil passages. Still won't cause water in the oil, but it made me think that maybe the intake manifold wasn't sealed up well enough and I'm getting water in that way.

So, I've pulled the intake manifold and am about to put it back on with new gaskets. My question is, do you folks think I should replace the head gaskets? It sure looks like a hassle, cuz i'll have to take of the exhaust manifolds and all of the lifters. Then again, I've already got the manifold off. Is there a way for me to pressure test it, without turning over the motor? I've seen some vague instructions in this forum on how to pressure test, but it's always decribed with engine slang I don't know, vague, and I never can quite understand how to do it. Any help is appreciated!!

Stan

 

[Bondo]

Re: Water in the oil - should I replace head gasket

Is there a way for me to pressure test it, without turning over the motor? I've seen some vague instructions in this forum on how to pressure test, but it's always decribed with engine slang I don't know, vague, and I never can quite understand how to do it.

Ayuh,.... Welcome Aboard,.... With the intake off, No pressure test,... not easily anyways...

(port side is new, the guy said he didn't winterize right and it cracked and had to be replaced, this was shortly after the rebuild).

You can change the head gaskets, but I'm thinkin' it's Deeper....

If ya Do,... Send the heads out from cleanin', checkin', 'n crack testin'...

 

[seapro17]

Re: Water in the oil - should I replace head gasket

Thanks Bond-o. That's exactly what I did, and I just heard back from the machine shop - one head is cracked.

Should I buy one new, or is one from a salvage yard okay? And if I buy one new, what material should it be? Does it need to be iron, or can it be aluminum? I'm sure the other head is cast iron, it's the original GM head. So should the other one be cast iron too? As you can tell, I know nothing about heads.

 

[wellcraft-classic210]

Re: Water in the oil - should I replace head gasket

You want to keep both the heads the same. A used one will offer savings but could have quality issues // so you may want to factor in that it should be inspected & may need to be repaired. Perhaps the machine shop your working with can advise you.

 

[Bondo]

Re: Water in the oil - should I replace head gasket

Thanks Bond-o. That's exactly what I did, and I just heard back from the machine shop - one head is cracked.

Should I buy one new, or is one from a salvage yard okay? And if I buy one new, what material should it be? Does it need to be iron, or can it be aluminum? I'm sure the other head is cast iron, it's the original GM head. So should the other one be cast iron too? As you can tell, I know nothing about heads.

Ayuh,... As noted, ya want a carbon copy of the head ya got,... Same Casting number, not close, the Same...

If yer gonna change ANYTHING 'bout the heads, it's gotta be done in Pairs, Twin sisters...

Also as noted, yer Machine Shop might be able to put ya into a set they've rebuilt...

 

[Don S]

Re: Water in the oil - should I replace head gasket

Did you check the area above the lifters for cracks?

 

[thrttlebkhtrod]

Re: Water in the oil - should I replace head gasket

I dont mean to be the "negitive nancy" here, but I just went through the same exact thing you are going through my friend. I wasted a ton of my time trying to trace a "water in oil" issue. I had a bad headgasket and a cracked head. Guess what, im putting a motor in because my problem is still there.. If you are doing it yourself and taking the time to do the heads etc.. Save yourself the headache and replace the motor. Also my set-up is a mercruiser 898.. Im upgrading to a 350

 

[seapro17]

Re: Water in the oil - should I replace head gasket

Thanks all for the input. What I ended up doing was - went to a salvage yard, got one with the same casting number (good call Bond-o!), hauled it to the machine shop, they checked it for cracks, pressure tested it, and cleaned it up. They also resurfaced both heads. Got 'em back about two hours ago. Now I'm going to put it back together this weekend. If I still have water in the oil, the only thing left is the block, but I really doubt I, since I didn't have water before, just steam. If I do end up with a cracked block, I'll just pull it. I actually have a newly rebuilt Mercury Racing 350 I could drop in, but it's from my performance boat and I don't want to separate those twins. So I'll just rebuild this one. But, I'm staying positive, I think this is gonna do the trick.

Thanks all!
Stan

 

[seapro17]

Re: Water in the oil - should I replace head gasket

Thought I'd update everyone on the status - in case anyone is curious. All the work I did fixed nothing. I can't tell if I'm still getting water in the oil, but I think I am. In addition, I now have even higher crankcase pressure - with oil coming out of the dipstick. I have high oil pressure and smoke billowing out of the crankcase vent tubes (with WOT). The only thing it can be I think is a cracked or porous block. This engine was rebuilt last summer, so it's got new rings, pistons and bearings. Rings could have cracked from water, which would explain all the blowby, but not the water in the oil. Could have a bad exhaust passages in the intake manifold, but that also wouldn't explain water in the oil. If I've got a cracked block, that would explain water in the oil, and I guess it could cause excess crankcase pressure, but I'm not sure about that.

So now I'm just trying to decide if I want to keep tinkering with it or just buy a crate motor. The thing is, this engine was just rebuilt and it has all new internal parts in it. Seems like a waste to toss it out.

 

[Fishermark]

Re: Water in the oil - should I replace head gasket

The thing is, this engine was just rebuilt and it has all new internal parts in it. Seems like a waste to toss it out.

It may have just been "rebuilt" - but obviously not well. Seems like it is time to cut your losses and buy another short block at the very least. That's if you are confident your heads are now good.

 

[TilliamWe]

Re: Water in the oil - should I replace head gasket

I'll admit I haven't read every post in here. But are your exhaust manifolds new also? What does the intake manifold look like?

 

[wellcraft-classic210]

Re: Water in the oil - should I replace head gasket

I recall a post frm Don S describing a cooling system presure test.

It seems you could seal off the inlets & outlets and try that as a way to verify the leak is present. If a leak is verified with a pressure test a tear down of the engine could be done ( the only cost being labor ) before deciding wether or not to purchase another.