MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

natemoore

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As some of you regulars know, I'm on my second season on a completely rebuilt 470. I'm not having any performance issues. In fact, I'm very pleased with how the engine performs. I used only OEM Quicksilver gaskets and other engine parts when not NLA.

One potentially disconcerting thing I've noticed is that if I top off the coolant tank, it always goes down about a 3/4" from then stays there. Also, every once in awhile, I'll get a ephemeral whiff of coolant when I'm cold cranking the engine.

Ooo that smell. Can't you smell that smell? Ooo that smell. The smell of [coolant being burned up in a combustion chamber] surrounds you.

I'm not immediately suspecting what you're thinking because that coolant smell is coming from inside the engine compartment, not the exhaust, as far as I can tell.

Here is a video of steaming boiling off the engine around the #4 cylinder. It could just be condensation evaporating. And aside from that initial faint, fleeting whiff of hot coolant, the odor goes away quickly. This steam doesn't really have any odor.

One other thing of note. I recently posted about having carbon fouled #3 and #4 plugs. Manual said that it was either sticking valves or bad spark plug wires, or extended periods of idling. Since my wires were very old and cracked, and I to let the engine run mostly at idle for twenty minutes at a time once a week if I don't use it, I replaced them. Got a nice set of Sierra from the iboats store. I'll report back if that fixed the carbon fouling problem.

Okay, would a pressure test of the coolant system be my first step? Should I rent a bore scope and look down into #3 and #4 for signs of coolant? Give me your opinions, guys.

http://www.youtube.com/watch?v=zFRE5tqwY98
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

Hoping to get this post back on Page 1.
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

My fellow 470 owners are letting me down :(
 

RandyJ

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

I'd pressure check everything possible...and start with a compression check of all the cylinders just to rule out the possibility of a cracked head or blown head gasket. Now, mind you, I don't run a 470 but do have one in an old junk boat out back that I'd love to have running but doubt there is a real possiblity of it.
 

EddiePetty

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

....just a suggestion:
Allow the engine to cool overnight. Open the doghouse and dab a dry paper towel scrap around the head-to-exhaust manifold gasket area in the vicinity of the exhaust runner. You're trying to confirm that the gasket is moist; which would lend me to believe you have a manifold-to-riser gasket on the verge of failure. That is, after a run and the engine is secured, residual moisture in the elbow seeps thru a failing gasket and puddles in the nearest exhaust runner.
Please don't laugh.....no one else seems to want to try!!!
 

RandyJ

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

Eddie... I'm not laughing at all! When I got into i/o's I drove myself crazy wondering how water was getting on top of the cylinders but I had great cylinder compressions... of course, you know that the inside of the exhaust manifold had cracked allowing water to come into the cylinders through open exhaust valves. I've ruined 2 good motors this way messing with my old junkers.... By the time I got educated on i/o mercruisers I had figured out how to make a bunch of gizmo's so I could pressurize exhaust manifolds to check for cracks in the cooling jackets.
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

Pressure test results:

Dropped from 14.8 psi to 13.4 psi in two hours.

Good? Bad? Marginal?
 

Don S

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

First thing you have to do is drain the coolant. Then do the pressure test.
Get a spray bottle of soapy water and spray around and look for bubbles.
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

First thing you have to do is drain the coolant. Then do the pressure test.
Get a spray bottle of soapy water and spray around and look for bubbles.

Oh. I thought I could pressure test with coolant in the engine. :( Bummer.

For what it's worth, after the sun went behind the trees, I pumped it back up to 15 psi and it held there for over an hour. Still there last time I checked. Probably not worth much from what you're saying.

I'm not suspecting an external leak. You know I'm getting that whiff of coolant at start up, but my coolant level doesn't seem to be going down. If it is it is imperceptible.

I think I need to pull off the reservoir/riser and exhaust manifold and check the manifold for leaks. I pressure tested it when I rebuilt the engine two years ago, but it's an old, tired piece of gear. If that's good, I'll reinstall and use the after-market Sierra exhaust riser gasket with a some RTV silicone instead of the OEM graphite/tin one I used last time.
 

telstar1

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

Try changing rad cap. Maybe its oozing out and running to the back of engine? Easy thing to try.Very common cap, all my farm junk uses the same cap....
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

I pulled off the reservoir/exhaust riser and exhaust manifold. Didn't see anything unusual. Gasket looked good. I'll pressure test the exhaust manifold this week. Today I conducted compression tests and cylinder leakage tests and got confusing results.

Now, if I said my compression in all for cylinders was 150 psi, you'd all say it was great. But, I got 170, 167, 165, and 150 in #1, 2, 3, and 4 respectively. I think they're supposed to be within 10% highest to lowest, so the 170 to 150 spread is a little concerning considering the rebuild is only two season's old. I was also thinking that #4 wasn't forming as good a seal with the compression tester as the others due to some rust and the squared off shoulder of the fitting (plugs have tapered shoulders).

Anyway, I did a cylinder leakage test next. For those of you unfamiliar with this, you put the piston of the cylinder to be tested at TDC on the compression stroke then basically pump compressed air into the cylinder via the spark plug hole. The gauges measure how much of the air pressure escapes past the valves and rings. These results were very good. All four cylinders were around 20%, which is in the "good" range on the gauge.

So, I think I can safely rule out a blown head gasket.

I'm not sure how much carbon should be inside the exhaust manifold. A swipe of the finger came away black. I wonder if I've got some carbon build up that is making the compression higher in the first cylinder?

Anyway, I'll post results of pressure test of exhaust manifold as soon as I do it.
 

joewithaboat

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

I have never owned one of these but have listened to friends whine about the quirks involved with them. As to the antifreeze smell, dont they have a weird two part seal that will dump coolant down the front of the engine if the first o ring is compromised? Could that be your smell / coolant loss.
I listened to your video, again i dont know much about these and i know video always sounds different than in person, but i think i hear some valve train noise. Sorry if these are off base again i have never owned or worked on one.
 

Don S

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

So, I think I can safely rule out a blown head gasket.

I wouldn't rule it out. Put the elbow back on, fill the cooling system and leave the cap off. Then retest #4 for leak down. Don't worry about the numbers, just watch for bubbles in the coolant reservoir.
 

guyaverage

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

I'll reinstall and use the after-market Sierra exhaust riser gasket with a some RTV silicone instead of the OEM graphite/tin one I used last time.

I wouldnt do that, unless its very temporary while messing around with this leak. Aluminum manifold against the iron riser....you really do need the graphite gasket.

One trick to try, if you want to find a leak start the engine up after dark and use a flashlight. Any moisture will reflect quite nicely against the light of a flashlight, and steam is very easy to track this way.

Have you checked the rear hose, the one that goes around back from the exhaust manifold to the intake manifold? Maybe the hose clamp is loose. Just a thought.

I watched your video, sounds exactly like my 470. Nice to hear someone elses rattling and knocking at idle like mine. Quiet as can be at anything above idle...
 

svxtech

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

On another thought, everyone seems to be caught up in an exhaust manifold problem. If you had an intake gasket leak and the antifreeze was leaking into the crankcase at a slow rate causing the smell to go away after it has been run and burned it off or through blow by...?..?...
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

I have never owned one of these but have listened to friends whine about the quirks involved with them. As to the antifreeze smell, dont they have a weird two part seal that will dump coolant down the front of the engine if the first o ring is compromised? Could that be your smell / coolant loss.
I listened to your video, again i dont know much about these and i know video always sounds different than in person, but i think i hear some valve train noise. Sorry if these are off base again i have never owned or worked on one.

I may as well recheck the lifter clearance and inspect the pushrods while I'm at it. Won't take but a half hour.
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

I wouldnt do that, unless its very temporary while messing around with this leak. Aluminum manifold against the iron riser....you really do need the graphite gasket.

One trick to try, if you want to find a leak start the engine up after dark and use a flashlight. Any moisture will reflect quite nicely against the light of a flashlight, and steam is very easy to track this way.

Have you checked the rear hose, the one that goes around back from the exhaust manifold to the intake manifold? Maybe the hose clamp is loose. Just a thought.

I watched your video, sounds exactly like my 470. Nice to hear someone elses rattling and knocking at idle like mine. Quiet as can be at anything above idle...

I was only going to use the Sierra gasket, which I already have, if I determined that the graphite/tin one leaked. I figured, what the heck, try something else.

I do have a little valve train noise. I'm going to double check clearances, torque, and pushrods while I'm waiting on the new OEM gaskets. Nothing like a little piece of mind.

I inspect my hoses and the front weep hole routinely. No signs of coolant leaks.
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

On another thought, everyone seems to be caught up in an exhaust manifold problem. If you had an intake gasket leak and the antifreeze was leaking into the crankcase at a slow rate causing the smell to go away after it has been run and burned it off or through blow by...?..?...

Coolant leaking into the crankcase would cause the oil to get milky. My oil still looks like maple syrup. :) I reckon it could get into the intake manifold air passage and be burned off that way. Luckily, intake manifolds aren't as expensive as exhaust manifolds, should it be proven to have a leak.

Coolant burning up in a combustion chamber has a very distinctive smell. It was what originally caused me to pull the engine and rebuild it, that and the billowing clouds of steam upon warm restart.
 

natemoore

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

I wouldn't rule it out. Put the elbow back on, fill the cooling system and leave the cap off. Then retest #4 for leak down. Don't worry about the numbers, just watch for bubbles in the coolant reservoir.

I should have done that before I took it off. I don't really need to use an exhaust manifold (to cylinder head) gasket for this test, just a good seal between the reservoir/riser and manifold with all the hoses hooked up, right?

Does anyone know why the #4 cylinder is the problem child of the 470? And is it possible to blow a head gasket without ever overheating the engine? I would bet my life that the temperature has never gone above about 160. One eye is always on the temperature gauge.
 

joewithaboat

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Re: MCM 165/3.7L/470 steaming near #4 cylinder upon cold start up (video)

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Remeber i have no specific knowledge of this motor... but as to the head gasket, was the head and or block surfaced, checked for cracks(magnifluxed)
Yes ive blown ahead gasket without overheating!
 
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