mercruiser coolant loss

[Hiskid]

Mercruiser 170, Alpha 1

previously posted regarding sterndrive reinstall because of shifting issues after impeller change.

boat was used last week, run hard pulling two tubers for about two hours, running fine. Upon attempting to return to the dock, it stalled, temp guage was up (about 3/4), would not restart. Metal coolant tank is empty, engine is covered with a thin residue (looks like oil).

Having read other posts with similar issues: 1) coolant loss; 2) bubbles visible in metal tank with cap off; 3) slight puffing out of valve cover breather to air cleaner, I'm guessing there may be a head gasket/related issue.

I have very little time to attend to this before its scheduled use in two days, pulling more tubers at a kids summer camp. If/since the engine already needs major work, would it be advisable to attempt to use it again (last day of the camp use this season), being very careful to monitor temp. gauge, and pausing to top up the coolant periodically?

The reason for the boat is for the kids, but I don't want to suggest to the camp director to do something which will cost even more in the long run.

Thanks ahead of time,
-Hiskid

 

[Hiskid]

Re: mercruiser coolant loss

Also, what about using one of the autoparts store products which claim to fix head gasket leaks-just as a temporary "band-aid" to get it through one more day?

-Hiskid

 

[Bondo]

Re: mercruiser coolant loss

Also, what about using one of the autoparts store products which claim to fix head gasket leaks-just as a temporary "band-aid" to get it through one more day?

-Hiskid

Ayuh,.... At the moment, you've got a probable repairable situation...

Run it another day, 'n you could very well end up with a big Anchor....

Yer choice....

 

[Eric 3.7LX Alpha 1]

Re: mercruiser coolant loss

I wouldn't.

where's the coolant going? in the engine oil or lake?

 

[Hiskid]

Re: mercruiser coolant loss

Bondo: ouch. Thanks.

Eric: oil looks fine (good color, not milky), but apparently was overfilled, currently is just above the word "full" (which is probably 1+ qt. above the top (safe) mark) on the dipstick. Another maintenance member changed oil before boat's last use while I was out of town last week. not much of anything in the bilge.

-Hiskid

 

[stonyloam]

Re: mercruiser coolant loss

Do a compression check and cooling system pressure check. If head gasket, it is a 1 day job to replace. Use a OEM Mercruiser gasket. If you run it again Bond-O is right.

 

[Hiskid]

Re: mercruiser coolant loss

I've put the ball in motion to acquire the testing tools suggested.

Pending the outcome of those tests, is there anything that should also be done/changed just as a matter of course while changing a head gasket?

I got a Seloc manual through this website; have heard mixed opinions on its usefulness and accuracy.

 

[stonyloam]

Re: mercruiser coolant loss

Use this manual: http://boatinfo.no/lib/mercruiser/manuals/mercruiser8.html#/0 and follow the instructions for head gasket replacement EXACTLY. Make sure you keep track of the pushrods to make sure they go back in the hole they came out of. NAPA (Permatex) Aviation Sealant is a good substitute for Perfect seal.

 

[Hiskid]

Re: mercruiser coolant loss

Cooling sys. pressure check: at 14 psi, pressure initially drops at about 1 psi per second. Hissing is heard in the #1 spark plug hole.

Compression check: #1-150; #2-150; #3-105; #4-140.

The data doesn't seem to completely agree.
Pull the head, check the heat exchanger (how?), something else?

I just learned that the head gasket had previously been changed about 5-6 yrs. ago, probably with one from an auto parts store.

Thoughts? Comments?

 

[r.j.dawg]

Re: mercruiser coolant loss

Also, what about using one of the autoparts store products which claim to fix head gasket leaks-just as a temporary "band-aid" to get it through one more day?

-Hiskid

That stuff is for cars....when you can walk away from a breakdown, which by the way will happen. You can't do that with a boat. And you have kids involved. :facepalm:
Should be a no brainer.

 

[Hiskid]

Re: mercruiser coolant loss

r.j.dawg, thanks for your concern. And two of those kids happen to be mine at the camp this week.

A little clarification. This is on a lake. A 40 hp Boston Whaler is readily available for rescues if needed. At this point, however, it looks as if the kids will be getting turns in the Whaler, not on tubes behind the Mercruiser.

Most of my experience working on boats is quite recent. Yes, I was openly looking for options this morning, but I pray to exercise good judgement, not foolishness. I appreciate the good advice I've received, including yours.

thanks.

 

[Hiskid]

Re: mercruiser coolant loss

Any more things to consider before pulling the head, or does that seem like the next logical step?

 

[nola mike]

Re: mercruiser coolant loss

Any more things to consider before pulling the head, or does that seem like the next logical step?

Someone correct me if I'm wrong, but could that also happen with a bad mani/riser gasket or riser leak? Depending on which exhaust valves are open. Maybe try turning the engine and repeating your test...and that #3 compression # isn't right, and doesn't go along with a leak at #1.

 

[Hiskid]

Re: mercruiser coolant loss

The compression numbers don't make sense to me, either; not in light of the cooling sys. pressure chk. I'll try the tests again, doing the compression tests first. Hopefully that will put the crankshaft in a different position for the cooling sys. pressure chk.

Stupid question: what is the mani/riser? Is it also called the exhaust manifold? I've heard the terms, but my experience is limited.

thanks.

 

[Eric 3.7LX Alpha 1]

Re: mercruiser coolant loss

I may be wrong but, if you could disconnect the two cooling hoses off the engine itself.. cap one end off, and pressure test the other hose, and only pressure test the actual block and head itself, it would show if the head gasket is to blame or not.

It would not be that difficult really. Take off both hoses to the engine, as shown on the attached diagram, and take them to your closest Plumbing supply company. Tell them you want to cap off one hose and make a pressure tester for the other hose. They will sell you the fittings you need to do it. Reconnect the hoses back on the engine only, with one end capped off and the other with a gauge and schrader valve connected with a tee, you could use an air compressor to test only the engine and head.

Just a thought

 

[Hiskid]

Re: mercruiser coolant loss

Good thought, Eric

I'll see what I can come up with

 

[nola mike]

Re: mercruiser coolant loss

Good idea eric, though it would be easier to turn the engine 90' and try again. But your method would take all the guesswork out.
@OP: Mani/riser gasket= gasket between the exhaust manifold and riser/coolant reservoir.

 

[Eric 3.7LX Alpha 1]

Re: mercruiser coolant loss

Good idea eric, though it would be easier to turn the engine 90' and try again. But your method would take all the guesswork out.
@OP: Mani/riser gasket= gasket between the exhaust manifold and riser/coolant reservoir.

Your Idea is what I've always thought as well, but just at the last minute I thought of that and figured why not?


Report back to us and let us know what you find either way so others will know who will be researching this thread!!

 

[nola mike]

Re: mercruiser coolant loss

Your Idea is what I've always thought as well, but just at the last minute I thought of that and figured why not?


Report back to us and let us know what you find either way so others will know who will be researching this thread!!

Actually, might be easier to do it the other way. Just plug the hoses coming from the reservoir-->engine, and use the pressure tester on the reservoir as usual. If that holds, you know your problem is in the head, and you can either continue with your idea or just replace the HG...

 

[Hiskid]

Re: mercruiser coolant loss

Update.

Upon pressure recheck of cooling system, the hissing noise seems to have migrated to Cyl. #2, without turning the engine.(?)

I had been so focused on the head gasket and its removal, I overlooked the great resource Stonyloam provided in his link. The Merc manual, specifically Ch. 6 cooling system explanations and tests.

The heat exchanger passed the pressure test (to my surprise).

After reading "Testing for cylinder head gasket leak" (p. 6A-5), I believed I observed the symptoms of head gasket/head/block issues on a previous test run: continuous bubbling/gurgling in the overflow reservoir. The manual states, "Compression tests or cooling system pressure check normally will not detect the leak because the test pressure is far below the combustion pressures which cause the leak." That's news to me. Perhaps that is the case with beginning or smaller leaks.

Gatorade bottles did a nice job of capping off hoses to/from the exhaust manifold to isolate for further testing. We initially forgot about the small air bleed hose between the intake manifold and the metal reservoir tank; it needs to be plugged off, too. Oops. Those test indicate another cooling system leak, I believe narrowed down to: 1) the metal reservoir tank, 2) the exh. manifold, or 3) the gasket in between.

Btw, tests were performed both wet and "dry," the pressure dropping much more quickly with just air. By filling the coolant sys. a little at a time, and testing at progressively higher levels, I believe I may have been able to approximate the level where the leak is occuring. I think its at or just above the gasket. I'd like to check things a bit more definitively...

Next will be to come up with a way to seal off the coolant passage between components to isolate them. Maybe a solid "gasket" in place of the original?