Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame???

rpeter46

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Hey-
My 1969 (ok, so it's actually the MC160, not 165) inline 6 showed me a chocolate milkshake the other day after a ride on the lake. I changed the oil, and ran it again on the hose, and it's got a little bit of water showing, but not a really nasty leak. It's my understanding that there are 2 possible culprits- a head gasket, or a bad manifold.

So what should I be looking for to properly diagnose each problem?

Paul
 

Bondo

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

Hey-
My 1969 (ok, so it's actually the MC160, not 165) inline 6 showed me a chocolate milkshake the other day after a ride on the lake. I changed the oil, and ran it again on the hose, and it's got a little bit of water showing, but not a really nasty leak. It's my understanding that there are 2 possible culprits- a head gasket, or a bad manifold.

So what should I be looking for to properly diagnose each problem?

Paul

Ayuh,.... The Most likely cause is a frozen cracked block...

The manifold can't put water into the oil, when Running....

'n a headgasket is an unlikely long shot....
 

Don S

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

It's my understanding that there are 2 possible culprits- a head gasket, or a bad manifold.

You missed the big reason, cracked block. Especially if you got water in it again while running on muffs.
 

HT32BSX115

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

Yeah, The 230/250 cu-in sixes frequently crack internally when all the water is not drained fully. Do you live where you experience freezing temps?

You should pressure test the block using air pressure. If it's leaking internally, you'll hear it.

Do a search in this forum. You find several threads on how to do it if you're not familiar.
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

OK, I'll check that first. I have to be honest, I know that it was drained over the winter, and I left the drain plug out of the block. However, if you think that is the first thing to check, I'll do that.

Paul
 

Don S

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

and I left the drain plug out of the block.

Did you stick a wire or something in the drain hole to make sure it was clear? On raw water cooled engines, they get covered up and don't drain by just removing the plug.
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

Did you stick a wire or something in the drain hole to make sure it was clear? On raw water cooled engines, they get covered up and don't drain by just removing the plug.

Yup. Raw water cooled, but I DID look for obstructions.

Don-I saw your helpful sticky about this condition. I didn't see any specifics on what to use to block off the water inlet, outlet, and where/how to inject compressed air into the block. Do you have any hints/tricks/tools to add to that? Thanks.

Paul
 

Don S

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

No specific info, use what you got laying around. Be creative.
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

So I need a threaded connection with a schrader valve and a second one with an air gauge? Where would you recommend screwing one in?

Paul
 

HT32BSX115

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

So I need a threaded connection with a schrader valve and a second one with an air gauge? Where would you recommend screwing one in?

Paul

Imagine you're just pressurizing an air tank with several different size openings.

You have to plug all the openings, connect a gage to one, and a valve and air compressor to another.

Turn on the valve and let it fill with air. (15-20psi or so)
(have the compressor off so you can hear the "hissing" after you turn the valve off)

That's all there is to it.

If you have external leaks, and you cannot see where, spray a little water on it mixed with dish detergent and look for bubbles.

If you have internal leaks, listen at the oil fill tube.

If you don't hear or see leaks (and the gage indicates that the "tank" is holding) you don't have any leaks!!


Good luck.


Rick
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

Thanks. I don't have all the pieces to fab up plugs and screw in a gauge yet. I did warm it up and check the compression. NO, I don't have previous numbers to compare them to. Anyways, they were:
1 - 130psi
2 - 135
3 - 135
4 - 135
5 - 135
6 - 95

Is there any insight that might be drawn from this - besides the obvious that #6 is low? Is #6 a regular source of leaking head gaskets? I know, I asked for help, and I haven't checked the pressure yet. Trouble is I have a compression gauge, and not the ability to pressurize the block yet. Stay tuned...

Paul
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

OK. I just gave the compression test a try. It took about 12 minutes to leak down, and I can't hear any leaking-even with my mechanics stethoscope. It was dark by the time I got to this point, so I need to check it tomorrow with some soapy water for the origin of the leak. It could still very well be some of the bottles and strange things I have plugging off the hoses.
Don S- can you comment on how long a good block will hold 12-15PSI? Forever, I assume... Thanks.

Paul
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

For anyone with experience running this test, can you usually hear the internal leaks, or do you just lose pressure? I did try listening down the dipstick as well.
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

I replaced a 43 year old hose and the leaking stopped. After an hour, I'm still holding at approx 13PSI. Does this give the block a clean bill of health? If yes, what should I check next? Thank you for all the assistance!

Paul
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

What should I check next? The block seemed to hold pressure fine, so can I get some direction on what is the next most likely thing to check for? Thanks.

Paul
 

Bondo

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

What should I check next? The block seemed to hold pressure fine, so can I get some direction on what is the next most likely thing to check for? Thanks.

Paul

Ayuh,.... I guess put it together, 'n Try it... Keep lookin' for leaks as ya go....

At 95psi on #6,... It ain't at all a Healthy motor...
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

Ayuh,.... I guess put it together, 'n Try it... Keep lookin' for leaks as ya go....

At 95psi on #6,... It ain't at all a Healthy motor...

Could the low pressure be related to a head gasket leak?
I'm just trying to figure out if it will help to have the head decked, and throw a new gasket on, or if that is just a waste of time and money. Don't mind doing it if it's likely, but if it's just wishful thinking, then I'll skip it.
 

HT32BSX115

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

Could the low pressure be related to a head gasket leak?
I'm just trying to figure out if it will help to have the head decked, and throw a new gasket on, or if that is just a waste of time and money. Don't mind doing it if it's likely, but if it's just wishful thinking, then I'll skip it.

It could be if you couldn't attribute it to a leaking valve.

Do a leak-down test on that cyl using compressed air in through the spark plug hole. Put it (that cyl) on TDC so both valves are closed........ If it's leaking past a valve you'll hear it in either the exhaust or intake port respectively.

If neither valve is leaking, it's either the rings or the head gasket. You'll probably hear it in the oil fill tube but rings always leak a bit.

If the block holds 13 psi you have no cooling system leaks.
 

rpeter46

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Re: Rootcausing Mercruiser 165 milkshake - What's to check first, and who's to blame?

Thanks, Rick. I'll check that asap. Appreciate the assistance.
 
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