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496 Mag HO with oil in coolant reservoir

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GVRBILL

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I have an 02 Monterey with a 496 Mag Ho. Today, I brought it up to the garage to start getting it ready for the season. Before initial start, I checked fluids. Oil looked great. It had not been changes since last spring. Coolant reservoir was an issue. I noticed a small amount of oil inside. I'm assuming I had been running it like that last season and didn't notice. Again, oil looks great. No sign of coolant and level was almost perfect. Any ideas what it may be or where to start looking. Engine runs great, no noises, no codes. Temperature and oil pressure are good.

Thanks
 
..."Oil...had not been changes since last spring."

Dirty oil is loaded with acids that eat away at the guts of an engine all winter long. The smart move is to change it before winter storage.

Jeff
 
Are you the only owner or did you buy it used? If the latter, you have no idea what kind of care was given. It's possible there was a problem at some point that allowed oil contamination of the coolant. It may just be trace leftover from that. Just keep a vigilant eye on it now that you've noticed it. It could be from oil cooler or steering pump cooler, which is better than cracked block!
And yeh you gotta change the oil at the beginning and end of the season and be sure to properly winterize.
There are two methods of winterization. One is total drainage of all water passages. The other is to completely fill all water passages with antifreeze.
 
o2batsea said:
Are you the only owner or did you buy it used? If the latter, you have no idea what kind of care was given. It's possible there was a problem at some point that allowed oil contamination of the coolant. It may just be trace leftover from that. Just keep a vigilant eye on it now that you've noticed it. It could be from oil cooler or steering pump cooler, which is better than cracked block!
And yeh you gotta change the oil at the beginning and end of the season and be sure to properly winterize.
There are two methods of winterization. One is total drainage of all water passages. The other is to completely fill all water passages with antifreeze.
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Thanks. I'll drain and flush the coolant and watch it. I purchased it 2 years ago so I do not know the history. And I'll be sure to service it after the season as well.
 
fastjeff said:
..."Oil...had not been changes since last spring."

Dirty oil is loaded with acids that eat away at the guts of an engine all winter long. The smart move is to change it before winter storage.

Jeff
Click to expand...

Jeff,
Thats a myth.
I have been doing spring only oil changes on hunders of boats for 30 years. No issues what so ever. My own boat for 26 years.

Also, when winterizing, i check out drive oil for water. If none I wait until spring to drain, pressure check and refill.

Again for 30 years and not 1 issue.
 
Sorry, Used engine oil is highly corrosive.......

Did someone top your coolant from the wrong container?


I would drain the coolant, flush it and fill with fresh.... Pay attention to oil level and see if it happens again. You can add tracer dye to the engine oil, if and when it gets into the coolant res again you can hit it with the UV light the dye will glow if it is engine oil...... The oil cooler on your engine is raw water cooled. Pressurized oil getting into a pressurized cooling system, if this is what is happening, is never a simple fix.
 
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Regardless, I have never seen, heard of one related issue for an engine sitting for 6-8 months....Not One.
 
Your the fisrt, maybe something to do with salt water engines...

What was the result of this that you have seen?
 
GVRBILL said:
Thank you. I'll drain, flush, fill, and watch it. If it continues, I'm assuming it's a head gasket.
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Probably a good test to do is to pressure check your coolant system.

I take it you have a closed cooling system with a heat exchanger?

If so acquire a coolant pressure tester and see if the system is integral. Most have a pressure of ~ 14-16 psi but the reservoir cap should show this.

If it holds pressure then I would say no leaks. If pressure bleeds off then you will need to find the leak.
 
kghost said:
Probably a good test to do is to pressure check your coolant system.

I take it you have a closed cooling system with a heat exchanger?

If so acquire a coolant pressure tester and see if the system is integral. Most have a pressure of ~ 14-16 psi but the reservoir cap should show this.

If it holds pressure then I would say no leaks. If pressure bleeds off then you will need to find the leak.
Click to expand...

Thanks. I plan on draining, filling, and pressure testing this weekend
 
GVRBILL said:
I'm not sure. And I don't remember physically looking in the coolant reservoir last season. I've only owned it for 2 years.
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That is why you should change the coolant with specified coolant and recheck it.

Oil into the res... is a rarity.. Exhaust into the coolant is more common..... 8.1's are pretty bullet proof to things like this....
 
Quick update. Drained and flushed the coolant. Had to remove the reservoir tank to clean it properly. Refilled system. Started it, got it up to temp. Ran it for 15 minutes...and no visible oil in the coolant. I'll have to get it out on the water and keep checking it. I still feel like something caused it, other tho. The boat was surveyed 2 years ago before I bought it and there was no mention of oil in the coolant.
 
Depending on how much oil was in coolant, the simple answer could be that when they filled it up the funnel used was soaked in oil.............Wouldn't be the first time for this to occur.

Again, I feel the only way to really tell is to pressure check the coolant system. This will tell you if here is any kind of leak.
As Chris said, typically it exhaust the leaks into the coolant. The only other path that I can think of would be a bad head or intake manifold gasket allowing oil into coolant BUT you would be loosing coolant more likely vs gaining oil...................
 
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kghost said:
Depending on how much oil was in coolant, the simple answer could be that when they filled it up the funnel used was soaked in oil.............Wouldn't be the first time for this to occur.

Again, I feel the only way to really tell is to pressure check the coolant system. This will tell you if here is any kind of leak.
As Chris said, typically it exhaust the leaks into the coolant. The only other path that I can think of would be a bad head or intake manifold gasket allowing oil into coolant BUT you would be loosing coolant more likely vs gaining oil...................
Click to expand...

I'll pressure test it this week. Oil still looks perfect too.
 
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