merc 5.7, low idle, stalling, milky oil in filler neck but not in oil pan

[jamanati]

Have a 95 3200scr, got it about a month ago. I dont know the history of maintenance. It has twin 5.7 with bravo 2. I initially changed oil, filter, cap, plugs, rotor, fuel filter. Been running okay. Today, dropping it into idle while coming into the marina, port engine stalled. Started it several times, I noticed idle was very low, around 300 rpm, compared to the stbd which is about 650. Putting it into gear would stall. I started it again, it revs up fine, but idles low, around 300. Water temp is fine. Got it into the slipt, and into the bilge I went.
I visually checked the carb, nothing really stood out. I noticed a yellow-ee substance on the valve cover flange. So I unscrewed the oil filler cap and its frothy white a bit. My blood pressure went up at this point. I checked with my mechanic he said to check the oil in the pan via the dipstick, which I did and that oil is fine, nice and clear since it was recently replaced only a few weeks ago, so there is no frothy white stuff in the oil pan. He said it may be leaking risers, to pull some plugs and check them. This may explain why it was idling low, maybe some water is getting onto a few plugs. I haven't done that yet, planning on it tomorrow morning. But a couple of questions to anybody in this forum that can help.
1) Mechanic said that sometimes the oil gets frothy because of some condensation and simply from the valves going up and down. First time I heard this. Anyone ever see/hear anything like this and is it something to worry about?
2) These are 5.7 mercs, anyone know the torque specs for manifolds and risers? I heard they have to be re-torqued after they get hot?
3) Any tips/tricks to replacing these? I already got one, when the first 2 bolts from the manifold are pulled, replace them with long studs, about an inch longer. This way when the other 2 bolts come out, the manifold doesn't fall or need someone to hold it. Then you can just slide it off the studs. And when putting back the new gasket and manifold, you can slide them back onto the posts. Any other tips?
4) Mechanic mentioned something about an oil blow-by? What is that?
Thanks all.

[mcoffey]

Hmmm, can't quite see how a riser could cause either of these issues. The only thing going through that is water and exhaust, it does not touch anything that comes in contact with oil or has anything to do with idle or fuel flow. Being that the milky substance is only in the filler nexk, I would say this is from condensation only. It would be good to clean it out in any case and keep a very close eye on it to come back and keep checking the oil via the dipstck, if it gets milky there, you have some issues (possibly cracked block or blown intake gasket. For thw low idle, I would check the idle screw to make sure it has not just backed out on you. It shouldn't but if it has a weak or no spring on it, it is possible it could vibrate out while you are running. You say it runs fine so doesn't seem like it is starving for fuel or timing issues so try just turning that idle screw and see if you can bring it up. Also make sure all carb linkage where cable connects and idle screw are look fine (not bent or missing or anything).

There is normally an oil blow by on these in place of a PCV valve. I have the 1996 5.7 2bbl and it has a black corrugated hose from each valve cover running up to the flame arrestor. So basically any oil blow by goes up the hoses and gets sucked into the carb. and out with the exhaust. Maybe if those were blocked off and there was no blow by, you could build up condensation when it was running.

Anybody else ever seen a riser leak water into the oil? Just never seen that on any engine much less a Chevy 350.

[cunuck]

I had the same problem on my 5.7 dip stick oil good but I had a leak in the intake manifold as well as the riser gasket.I would pull the intake and risers and change both gaskets before you do more damage.I put new risers on just to be sure no water leaks.I only had 240 hours on my 5.7 the merc gaskets are not the best.good luck

[jamanati]

Well, I spent the day in the bilge. Pulled and replaced both manifolds and risers on this motor (port side). Pull the valve covers off as well and cleaned out the white gunk, tomorrow I'll change the oil and filter. While I was doing this, the mechanic lent me his compression guauges. I had pulled the manifold and riser from the right side of the motor, so it was easy to run the tet. PSI on those 4 cylinders ran from 140 to 170, which I tought was fine. I then did the other side, which still had the riser and manifold on. 3 of the 4 also read fine, about 150. But the 2nd cylinder from the front pegged the guage to 250. I tried other cylinders after that, the guage read those fine around 150. Went back to the 2nd cylinder, guage read about 230 psi. Spoke to the mechanic, he never really heard of this condition. So, I took that riser off and saw some water in the manifold. After a few hours I put it all back but didn't have the guage any longer to re-read the cylinder. I'll try that tomorrow. But anyone ever see this condition where all 7 cylinders are pretty in spec (150-170 psi) but one cylinder goes to 230+? I read about timing, but that would effect all cylinders, wouldn't it? Not just one. I've heard about low compression, but never high compression in just one cylinder. The rockers and rods look okay. Inside the valve chamber, normal stuff, nothing stood out.

[cunuck]

Sounds a lot like my 5.7 only I never saw the milky oil at first .The motor ran great a low rpm so I thought it was fuel or plugs .I ran it for a few min and blew the head gasket between 2&4 cyl and did some damage to the piston. The head gasket on the other side was ready to go between 3&5.When I removed the intake manifold cover and valve covers is when I saw the milky oil of death.I checked the dip stick every day and no sign of oil????.In check around I found merc head gaskets are crap and risers can be a problem .If you can't get even compression I would check the head gaskets it might save you a rebuild if they blow. Easy to change now.You can also have your riser and exhaust manifolds tested for leaks.I can send you a photo if you want of my intake and valve covers if you want.Good luck

[seapuppy]

Wow...a compression test of 250lbs???....there is something definitely wrong there.....not sure waht to say about that ...I've always seen the compression test fail......

that's got me bugged....it could cause some serious damage like blowing the head gasket or even bend the rod......hmm....I'll have to contact some mechanic friends about this one...

SP

[ss3964spd]

Wow, 230 PSI in that hole? Can only be explained by something occupying space in that cylinder - likely water. There is nothing else that can explain that high of a reading except for the far fetched possibilities that when the engine was built someone installed the wrong piston, or the cam shaft lobes for that one cylinder were ground incorrectly, but if that were the case the engine would have suffered pre-ignition (pinging) like mad.

If you cannot figure out whats going on I'd suggest you get a scope, snake it in through the spark plug hole, and have a look in there.

Dan

[jamanati]

The scope is a good idea. I turned it over a few times with the plug out to clear out any thing, but its on the port side of the port motor and trying to get my head down there to look through the hole wasn't something I thought of. Thanks for the tip on the scope, will take a look. Now as part of my checks, instead of just relying on the dipstick, I'm adding to take a look at the oil filler holes. Previous owner did say the motors only had 200 hrs on them, and when I pulled the valve covers off, it all look really new, no rust, gasket was in great shape, only the milky gunk was the issue. But probably he didn't replace the manifolds or risers at the time. I have read where carbon deposits can cause high compression, but I would think more than one cylinder and on an older engine. On to the scope idea, I'll post what I'll find, but it probably wont be until Saturday.

[ss3964spd]

If you can't scope it, J, see if you can use a small diameter flexible tube connected to a cheap syringe. Remember that the piston tops are tilted at 45* so the low side - where any water will collect, will be towards the outside of the block so snake your tube in there accordingly. If you draw any water out then you won't need to scope it.

You are right, carbon build up would normally affect all cylinders, unless there is one mis-firing. Regardless, it would take an awful lot of carbon build up to raise the cranking cylinder pressure that much.

Dan

[jamanati]

Got back to my boat, pulled the plug out and stuck a syphon hose, nothing came out. Cranked it a few times and was pretty clean. Compression test now says 150psi. Well, whatever that issue was, its gone now. Change the oil/filter, had some water in the oil filter but no gunk. Lets see how my test drive tomorrow goes.

[jamanati]

Test drive went well, was out all day. Oil pressure is good, no leaks, checked it when I got back, looks good as well. Everyone, thanks for your help and ideas.