6.2L MPI Horizon MIE Oil Analysis Shows Antifreeze

[Lou C]

Agreed they look good, what are your compression test results?

 

[Greg_E]

Sorry for the long delay but I've been busy getting the boat covered so I haven't had time to work on the engine.
When I was at the boat I retrieved my compression tester and brought it home to verify the gauge was reading correctly, and it is .
So here is the bad news. Last year the compression in all cylinders was 140-145 in all cylinders. When I tested it this year I could not run the engine prior to testing and temps were in the mid 40's. I don't know how much that might affect the readings but my guess is not all that much. This time, all compression readings are within 8 lbs but are reading between 72-80 with most of them between 75-80. #6 was the low one at 72. . Each cylinder was tested at least twice with the throttle plate wide open. The fact that all cylinders are low makes me think that the damage is widespread. and not easily fixed. Any thoughts on that?
My next step is to use the new radiator pressure tester to try to pinpoint what caused the antifreeze to get in the oil, so If I get a warmer day I'll see if I can get that done.
If I don't find anything what would be the next step, cylinder leak down test?

 

[alldodge]

Normally I would expect some but not all to be low compression, and also would not think temp would low numbers by 30%

Pressure testing cooling system would be good to know in the decision tree

 

[Lou C]

Interesting, with the plugs looking like they do (not oil fouled) I would not expect worn rings. Maybe you have valves not seating due to lack of use and the cold. I would do a leak down test, that will tell the tale, if you find its valve related you could remove the heads over the winter and have them done over by a machine shop and reinstall them. Not a bad job but you need to clean everything really well and keep all the parts organized. And if your antifreeze in the oil is head gasket related this will show it one way or the other....

 

[nola mike]

I can't think of anything that would cause those compression numbers and still leave you with a running engine. Especially since they're in both banks. I'd double check your tester (new tester or different engine). Leak down test might also be of value.

 

[Greg_E]

I can't think of anything that would cause those compression numbers and still leave you with a running engine. Especially since they're in both banks. I'd double check your tester (new tester or different engine). Leak down test might also be of value.

I was surprised by those numbers as well. That motor always starts right up.
I did check the compression tester gauge by plugging it into my small compressor. The reading was a couple pounds less than the gauge on the compressor tank, so I would say it is accurate. I'm sure the gauge on the $100 compressor is no precision instrument.

As Lou C and others have said the plugs don't look bad so hopefully the rings and cylinder walls are still OK.

I got down to the boat today to finish up covering it. for winter. I had to make a special frame so I can lift the hatch to get at the engines and still be able to get in and out of the boat.

I only had about a half hour before I had to leave. I did use the Stant radiator pressure tester and tried to listen for a leak in the throttle body, around the manifold, dipstick tube,and oil fill cap, but did not hear anything. I let it sit while I picked up to leave and after 20 minutes the needle may have dropped just a hair. I need to leave it longer next time to be sure. If the leak is that slow I doubt I will be able to hear anything.

So it looks like I have to solve two problems. Where is the antifreeze getting in the oil, and why is the compression so low in all the cylinders? I can do a leak down test if it warms up and I get some time. It was like standing next to two blocks of ice in the engine compartment today. Warmer outside today but freezing cold the last two days..

Here are the elements that were reading high in the oil test report. This is only the 2nd oil test I've had done, so I am just going by what I was told or read in a couple articles.

Potassium 68 average is 4
Sodium 658 average is 4
Those would be the antifreeze in the oil

Copper 22 average is 8
Lead 142 average is 7
Tin 9 average is 2
Those would be bearing wear

Chrome 4 average is 1
Ring wear

Iron 239 average is 36
Cylinder walls

Aluminum 8 average 3
Don't know

 

[alldodge]

The copper and aluminum numbers have me concerned due to bearings

 

[Scott Danforth]

Check the compression gauge. Motor wont run with compression that low

Agreed on the copper/aluminum/lead

 

[Greg_E]

I agree things are not looking good. I wish I could get to a point where I can make a decision on what needs to be done and move on from there but the weather has not been cooperating. and I have some other thing that are keeping me from getting down to the boat.

I did bring the compression gauge home and plugged it into the small compressor in my garage for airing up the tires. It was within 2 lbs of the gauge on the compressor tank. It's a used Snap-On gauge I picked up, so it is good quality, i just had never used it prior to this. The engine did start easily when I winterized it so I am at a loss to know why the compression is reading low, yet it started right up.Time to take a step back and try to sort that out.

While the bearing metals were high, the oil pressure was good even at idle. I don't remember the exact number but if it was 10 lbs or less at idle I'm sure I would have noted it. Cruising it was around 40. Hopefully the excessive bearing wear has only been happening for a short time and if I can find and fix the source of the problem, it will be OK for a while..

 

[Greg_E]

We had some warmer weather today so I got down to the boat. I pulled the valve covers and repeated the pressure test on the cooling system. I also purchased a mechanics stethoscope. I still did not see any drop in pressure or hear any leaks. I retested a couple cylinders and they were still low. Those things along with the metals in the oil makes me think it is time to just get on with repairing this. I bought this boat because I was tired of fixing my old boat, so I'm going to start taking it apart and see what I find. I just want a reliable boat for next season.

I'm thinking about having a long block built, and do the swap early spring. I have a reputable shop in mind. I think I can have a motor with better parts and quality workmanship vs what is in the boat now.

When I find the source of the problem I will post in this thread.

I'm going to start a new thread (tomorrow) " 6.2L Rebuild " or something similar. I have a lot of questions regarding parts sourcing and any tips to help this go smoothly.

Thanks to all that offered advice.

 

[Scott Danforth]

its a GM motor. new 377 long blocks are $4200
if you build the motor your self, you can build the longblock for about $3500
to refresh what you have with new slugs, etc your in the $1500 range

to pay someone to pull the motors and tear them apart, etc expect pricing to be 3x the cost

 

[Greg_E]

Unfortunately I have no way to remove and replace the engine myself. I have to pay the yard to do that and that isn't going to happen until spring.
I looked at the GM 377 long blocks but I think I can get a long block built with better parts for about the same price or maybe a little more. Your thoughts on that? I can swap all the parts from old to new and hook everything up.
We are supposed to get some warmer weather this weekend so I hope to get to the boat and pull the intake manifold and at least one head to see what's up.

I started a new thread related to the rebuild here.
https://forums.iboats.com/forum/engi...dations-needed

 

[Scott Danforth]

if you have a way of re-programming the ECM, you can build 420hp motors easy for $4200 each using new blocks and heads. about $2300 each using your blocks and heads. without re-programming, no sense to use "better parts" as it wont mater.

requires these simple changes:
LCQ style pistons (vs the flat top 4-relief stock units)
modify the heads for higher lift cam, mild porting and bowl blending
coated bearings
different cam (using the same 1.6:1 rocker ratio, however with a better profile)
roller timing set
throttle body spacer

 

[Greg_E]

if you have a way of re-programming the ECM, you can build 420hp motors easy for $4200 each using new blocks and heads. about $2300 each using your blocks and heads. without re-programming, no sense to use "better parts" as it wont mater.

requires these simple changes:
LCQ style pistons (vs the flat top 4-relief stock units)
modify the heads for higher lift cam, mild porting and bowl blending
coated bearings
different cam (using the same 1.6:1 rocker ratio, however with a better profile)
roller timing set
throttle body spacer

I don't have a way to reprogram the ECM. I can't say that I've seen any mention of tuning software for the Mercruiser ECM but someone must be doing it. I'm only doing the one engine for now so it would not make sense to have one 320HP and the other 420HP.

I started a thread for the rebuild so if you can post in that we can avoid jumping from one to another.
https://forums.iboats.com/forum/eng...pi-horizon-mie-rebuild-recommendations-needed

 

[Scott Danforth]

then keep it stock, and keep it simple. have the replacement crate engine ready, when you pull your current engine, swap over the accessories and stab the new engine back in. that way your renting a hoist for a day.

 

[Greg_E]

I think I may have found the source of the antifreeze in the oil. When I pulled the intake manifold, this is what I found. The other bank was about the same. Hard to believe that the cooling system was holding pressure when I tested it, but in the cold weather, I guess everything tightened up enough that it didn't.
I also found some build up in the two middle coolant ports of both exhaust manifolds. That probably wasn't helping the situation. I'll post a couple pictures of that in a shortly.

 

[Greg_E]

Here are some pictures of the exhaust manifolds. When I first removed the manifolds I thought it was rust as it was orange, but as it dried it it has become more gray. Can those deposits be removed and the manifolds reused? Other than that, there is really no sign of rust other than the light surface rust seen in the 2nd picture.

 

[alldodge]

Head might need to be machined to get it all flat

Clean the exhaust out then determine if it can be reused

 

[Greg_E]

Head might need to be machined to get it all flat

Clean the exhaust out then determine if it can be reused

Is there anything that will dissolve that without attacking the cast iron? If not I can use a carbide cutter. Just need to be careful. Is it common to see a build up like that in a closed cooling system and what causes it?

While we are on that subject, do the stainless steel gaskets that go between the manifold spacer and riser need to be replaced every time they are removed? They are all in good condition except for the graphite compound that is on both sides of the gasket.

If I decide to reuse those heads I will be sure to tell the shop to check both surfaces. I would guess the intake manifold surfaces should also be checked. I will be reusing that.

 

[Scott Danforth]

Is there anything that will dissolve that without attacking the cast iron? If not I can use a carbide cutter. Just need to be careful. Is it common to see a build up like that in a closed cooling system and what causes it?

While we are on that subject, do the stainless steel gaskets that go between the manifold spacer and riser need to be replaced every time they are removed? They are all in good condition except for the graphite compound that is on both sides of the gasket.

If I decide to reuse those heads I will be sure to tell the shop to check both surfaces. I would guess the intake manifold surfaces should also be checked. I will be reusing that.

oxalic acid - pull head apart, soak in oxalic acid for a week, rinse with water, rinse with baking soda and water, then take to machine shop.

yes, gaskets are a one-time use

perfect



on another note, new vortec heads are about $900 a pair, a bit less if you wait for a sale.