mercruiser coolant loss

[stonyloam]

Re: mercruiser coolant loss

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.

That along with low compression on #3 seem to indicate a head gasket problem. I believe that it is very important to use a OEM Mercruiser head gasket, and while you are at it replace the manifold/exhaust elbow gasket. What is the year/sn of the engine?

 

[nola mike]

Re: mercruiser coolant loss

That along with low compression on #3 seem to indicate a head gasket problem. I believe that it is very important to use a OEM Mercruiser head gasket, and while you are at it replace the manifold/exhaust elbow gasket. What is the year/sn of the engine?

I dunno, me and Terry seem to disagree on when to replace the HG--I think I'm lazier

You for sure have a gasket/riser problem. There is going to be *some* gurgling in the reservoir as it cycles. Don't have the manual in front of me, but IIRC the HG test is a bit more involved--maybe placing some clear tubing somewhere. The moving leak and compression still don't make sense. I also think it's OK to use a cheap felpro auto gasket (I'm cheaper than Terry as well).

 

[stonyloam]

Re: mercruiser coolant loss

I also think it's OK to use a cheap felpro auto gasket (I'm cheaper than Terry as well).

Totally disagree on that one. The Mercruiser gasket is designed specifically for the 470 and has additional sealing features that the aftermarket ones do not. The hot rod guys that use the 470 engine (including one land speed record racer) say OEM only, so for the $40 difference I would not take the chance.

On compression #3 is 45 low and #4 10, so unless they come up significantly with a little oil added, the head is going to have to come off anyway.

 

[nola mike]

Re: mercruiser coolant loss

Totally disagree on that one. The Mercruiser gasket is designed specifically for the 470 and has additional sealing features that the aftermarket ones do not. The hot rod guys that use the 470 engine (including one land speed record racer) say OEM only, so for the $40 difference I would not take the chance.

Fair enough. In most applications the HG are the same, wasn't aware of a difference on the 470. What are the add'l sealing features? Any links to pics? We'll see how mine holds up.

On compression #3 is 45 low and #4 10, so unless they come up significantly with a little oil added, the head is going to have to come off anyway.

Well, #4 is not out of line. But yeah on #3. Anyway, draining the coolant is probably the hardest part of the HG change.

 

[stonyloam]

Re: mercruiser coolant loss

Well, #4 is not out of line. But yeah on #3. Anyway, draining the coolant is probably the hardest part of the HG change.

I will agree on that one. Have been thinking about how to do that. I think you could take a funnel and hose. Run the hose out through the transom drain plug, put the funnel under the heat exchanger antifreeze drain (the forward plug) and drain it into the funnel and out through the tube into a container. I think that will get most of the AF out of the head and manifold. There is another drain on the side of the block, but I don,t know how to catch the AF coming out. May be able to just crank the engine over and pump enough out of the block into the exchanger so you can do the head.

 

[stonyloam]

Re: mercruiser coolant loss

Fair enough. In most applications the HG are the same, wasn't aware of a difference on the 470. What are the add'l sealing features? Any links to pics? We'll see how mine holds up.

Here it is http://www.mercruiserparts.com/showSpecialPicture.asp?pn=13709 the light colored lines on top and along the bottom appear to be red silicone beads, and I assume are there to help seal the iron head to the Al block. I think aftermarket heads are automotive gaskets designed to seal a iron head to a iron block. The automotive gasket might just work fine, but why take a chance?

 

[nola mike]

Re: mercruiser coolant loss

I think you could take a funnel and hose. Run the hose out through the transom drain plug, put the funnel under the heat exchanger antifreeze drain (the forward plug) and drain it into the funnel and out through the tube into a container. I think that will get most of the AF out of the head and manifold. There is another drain on the side of the block, but I don,t know how to catch the AF coming out. May be able to just crank the engine over and pump enough out of the block into the exchanger so you can do the head.

Yeah, I'm always shocked at how much I end up with after draining the exchanger and the reservoir (via a coolant hose) still in the block. I like the idea of leaving the plug out of the exchanger and cranking the engine...I'll try that next time.

 

[Hiskid]

Re: mercruiser coolant loss

It almost sounds as if head gasket replacements are a regular occurence on these engines. I've heard about overheated aluminum heads being warped on removal from cast iron blocks. How does that play out when the metals are reversed?

I see I really should do more "wet" compression testing to determine if rings are to blame for the low cylinder. Thanks for the reminder.

Also, sounds like coolant draining is quite a challenge. Is just draining and flushing it out of the bilge afterward a no-no?

 

[nola mike]

Re: mercruiser coolant loss

Not challenging, just messy. And do it enough and it gets pricey. And annoying. And it's tough to find someplace that accepts used a/f. Letting a/f just drain into ground/lake/etc is a no-no. And my HG repair was because I needed to remove the head to replace a valve. Doesn't seem like the HG fails too often as long as the engine doesn't overheat. AFAIK mine was original.

 

[stonyloam]

Re: mercruiser coolant loss

It almost sounds as if head gasket replacements are a regular occurence on these engines. I've heard about overheated aluminum heads being warped on removal from cast iron blocks. How does that play out when the metals are reversed?rings are to blame for the low cylinder. Thanks for the reminder.

They are more prone to HG problems because of the open deck and Al/iron combo. That is why it is critical to avoid overheating. Mine is an 87 and have done the HG once. most of the problems occur when the cooling system is neglected. Changing the impeller every other year is a very good idea, along with carefully monitoring the temperature gauge. Keep your reservoir full with 50/50 antifreeze and if it starts to disappear, find out where it is going, sometimes not very easy LOL. Yeah the ol 470 will keep you on your toes. Good luck.

 

[Hiskid]

Re: mercruiser coolant loss

Update.

Did a little more testing to try to determine if the leak was the head gasket, or elsewhere. The head was isolated from the rest of the cooling sys. by removing and capping coolant hoses using gatorade bottles. With a little oil added, "wet" compression numbers all came up, but #3 was still low (I don't have the numbers in front of me).

The heat exchanger had previously "passed" the pressure test, and was left connected to the exh. manifold and metal coolant reservoir. This combo was still leaking as previously mentioned. To further isolate the components, I made a "solid" gasket (no holes) for the exh. manifold-reservoir tank connection. The tank was then pressurized using the cooling sys. pressure tester (Autozone tool): no leaks, even with just air at 30 psi (max pressure for testing tool).

One of the gatorade bottles connected to the exh. manifold was replaced with an assortment of PVC fittings we had on hand to make a cap. An automotive style tire valve was installed in the end cap and pressurized with a bike pump. It quickly leaked down, hissing being heard at the gasket connection to the reservoir tank. After gasket sealant was added to the"solid gasket at the tank connection, the pressure held reasonably well.

It seemed like there was enough evidence to justify pulling the head, in addition to there being a gasket-sealing issue between the exh. manifold and reservoir tank. Upon disassembly, there appears to be evidence of leakage at cyl. #3, and to a lesser extent, #4. The sealing surface of the block is darker in a portion, and below these places the outer wall of the cylinders (at #3 and #4 inside the coolant jacket) is darker in color. The block and head check out fine (less than .003") for warpage, with the exception that the "bosses?"/threaded holes portion for the head bolts in the block are high (around .006") between cyl. #2 and #3.

The current plan is: 1) all new Mercruiser-brand gaskets; 2) resurface both pieces where the exh. manifold and reservoir tank join together.

Lots of great discussion and suggestions so far. You can probably see some version of many ideas being used in some form or another.

Thanks so far, guys.

 

[stonyloam]

Re: mercruiser coolant loss

You might ask your machinist about hardened exhaust seats, see what he thinks. I did mine, but I also had to have some valve work done because of coolant leaking into the #4 cylinder. Sounds like you are doing just fine, those kids will be enjoying that ol 470 for lots of years to come.

 

[undercover]

Re: mercruiser coolant loss

Use this tool to determine if you have a blown head gasket:

Www.blockchek.com

It detects exhaust gasses in the cooling system. Too bad it doesn't work on a raw-water cooled system.

 

[Hiskid]

Re: mercruiser coolant loss

Update:

Had the bottom of the reservoir tank and the exhaust manifold resurfaced. The opinion of the machine shop was that it would have been impossible for the exhaust manifold not to leak at that connection. The engine is back together with the exception of a few odds and ends not crucial to operation. Cooling system pressure checks fine. Lord willing, this is the day...

 

[stonyloam]

Re: mercruiser coolant loss

Great! When you get it running on muffs, run it long enough to come up to temperature, then shut it down and retorque the head bolts. The book says run it up to temp, but does not say when to retorque, hot, or after it has cooled, and there is some debate as to which to do. Some of the guys do it after the engine has cooled, I did it while the engine was fairly hot. Not sure which is correct but mine is fine and theirs seem to be fine, so I guess the important thing is that you do the retorque. The rocker arms are supposed to be retorqued too, but they have to be loosened to retorque the head, so I guess after you retorque the head you have to do it all again and retorque the rocker studs. With it running all of the pushrods should have oil coming out of then. Good luck, there is still plenty of summer left. You will develop a love hate relationship with that ol 470, and it will defiantly improve your mechanical skills.

 

[Hiskid]

Re: mercruiser coolant loss

Hey everyone! Sorry I didn't post this sooner; been a little busy.

Bond-o, Eric, stonyloam, r.j.dawg, nola mike, undercover, Aussie chris (youtube videos about sterndrive, cable adjustment, etc.) thank you all very much. Your wisdom and technical advice are priceless. Some of the things I didn't really want to hear at the time, but friends tell you what needs to be said, not always what you want to hear (Faithful are the wounds of a friend). That's why I say, "Ouch. Thank you." The boat's running great and now has about 12-15 hours on it in various uses.

You can see the camp where it's used at cbmcamp.com. The boat had been down for 2 years; looks like they need to add "tubing" to the website's list of activities...

thanks again,
Rick

 

[Eric 3.7LX Alpha 1]

Re: mercruiser coolant loss

Glad to hear it running great and back in service!!