470 leaking. Sigh.

[nola mike]

I've had a leak on this thing damn near since I bought it 5 or 6 years ago. When to start it for the first time. Pulled the valve cover, all looked fine. Pulled the plugs and turned over, and...a/f gushing from #4. Is there any place other than the riser/mani interface that this could be leaking? The riser is a couple of years old. I had the manifold surface machined when I replaced the riser. I'm not sure if it ever completely stopped leaking, it isn't really noticeable unless it sits for a while. I tried to ignore it last year, but would like to fix it this season (again). I hate draining the whole damn system--I think I'm going to pressure test, drain coolant, and repeat until I hear the leak. If it's that gasket interface, I figure I should be able to hear it right away. Trying to see if I'm forgetting a potential leak point here.

 

[nola mike]

Re: 470 leaking. Sigh.

Well, unable to isolate the leak exactly, but I could hear hissing in #4 (no surprise). Didn't hear anything in the reservoir. Is there anywhere else other than the res/mani gasket that this could be leaking? I had the manifold surface machined and replaced the reservoir 3 years ago, and have had the reservoir off more recently than that...
In other news, I pressure tested the outdrive (I didn't know if I imagined some milky oil last year), and got 'er fired up, seemed to run fine. Couldn't figure out why I initially wasn't getting spark--new plugs, cap, rotor. Oh, right. Can't use standard rotor with the electronic ignition :facepalm:

 

[achris]

Re: 470 leaking. Sigh.

Head gasket?

 

[nola mike]

Re: 470 leaking. Sigh.

Most of the coolant loss happens when the boat is sitting--I lose very little (at least last year) when underway. Haven't checked compression this year, but was fine last year. I'd think that a HG leak big enough to leak unpressurized coolant into the cylinder would also be big enough to mix with oil, or blow back into the coolant system under load, or something. Or is that not the case?
Also, HG was replaced 3y ago as well. Have never had an overheat. If HG still a suspect, how can I narrow it down?

 

[achris]

Re: 470 leaking. Sigh.

Leakdown test.

 

[nola mike]

Re: 470 leaking. Sigh.

Will do this weekend...

 

[nola mike]

Re: 470 leaking. Sigh.

Thinking about this a little more. If I were to move the engine to TDC (or rather the #4 cylinder) and then pressurize the cooling system, I can think of 2 things that may help me pinpoint:
1) My leak will be gone, depending on how well my exhaust valves seat, if it's a leak in the manifold. HG leak wouldn't be affected by valve position, right?
2) The sound of the leak will at least change as I rotate the engine.

I'll still do a leakdown test, but I'm afraid that either my #4 cylinder will be worse than the others (from years of leaking, my bent pushrod a couple of years back, etc) for other reasons than a coolant leak, or that all 4 cylinders will look tired. Still good info if it's there, but nothing I'm going to do anything about this season.

 

[bansheejoel]

Re: 470 leaking. Sigh.

Wiiling to bet money your exhaust manifold is cracked. When your cooling system is pressurized it will weep into the cylinder

 

[nola mike]

Re: 470 leaking. Sigh.

Okay, so did the leakdown test. Not sure how to interpret it though.
Cylinder 4 was 28%, whereas #1 was 21%. Didn't have time today to do the other 2 cylinders. This was on a cold engine. Couldn't hear a leak anywhere. I definitely didn't hear anything in the coolant reservoir. #4 has lived a bit of a rough life since I've had the boat, with valves being rusted shut, and sitting this winter full of antifreeze. So could be worse I guess. On my meter up to 40% is in the "slow leak"/green portion of the meter. Don't know if this means anything, but the leak % didn't change when I pressurized the coolant system. Nor did the pressure drop on the coolant system change based on the position of the #4 cylinder.

Anyway, I know I most likely have a tired engine, but do those numbers point to a head gasket, or is it just rings/valve leakage?

 

[nola mike]

Re: 470 leaking. Sigh.

Any thoughts?

 

[achris]

Re: 470 leaking. Sigh.

Any thoughts?

Yep, I'm thinking of a nice warm beach, somewhere in South-east Asia, with dancing girls, cold beer, and no worries about work, money, taxes....

Oh, oh, you meant about your engine... Nope, none... But I did find an excellent article on leakdown tests.. How to do Cylinder Leak Down Testing- Car Craft Magazine Page 2

As for the coolant leak, it is possible to have a crack that only opens up in a specific temperature range, or pressure range. I have seen that before too...

 

[Eric 3.7LX Alpha 1]

Re: 470 leaking. Sigh.

Which exhaust manifold do you have cast or Aluminum?

Is there any way you can pressure test smaller sections of the cooling system at a time, and see which section isn't holding?

This is what the manual gives for possible loss of coolant:

of that list which options could cause cyl 4 trouble? I'm thinking D,E,F, and H

Which could cause only cyl 4 trouble? D,F,H?

If you could isolate the actual block and pressure test just that. that would narrow it down.

 

[nola mike]

Re: 470 leaking. Sigh.

@ Chris: I can arrange everything above except for the South-east asia part. The dancing girls insist on a non-leaking boat however. I actually had already come across that article when I was looking into the leak testing. The leak is time-dependent, not pressure or temp related (if I take it out all day it loses very little, but I get much more loss after sitting for a couple of weeks--or a couple of months).
@ Eric: Yeah, that's a good idea. Maybe I'll get some gasket material and a steel plate, screw it down after removing the reservoir and see what happens. "block porosity" would be a *****, huh? Or I might just replace the res gasket and try to pressure test again first. That would probably be the easiest route.

 

[achris]

Re: 470 leaking. Sigh.

I've never heard of porosity in a 470... Mainly because it's a cast ali block... With steel cylinder liners. If the block was porous to the crankcase area, you'd see water in the coolant, which you are not.

 

[Eric 3.7LX Alpha 1]

Re: 470 leaking. Sigh.

@ Chris: I can arrange everything above except for the South-east asia part. The dancing girls insist on a non-leaking boat however. I actually had already come across that article when I was looking into the leak testing. The leak is time-dependent, not pressure or temp related (if I take it out all day it loses very little, but I get much more loss after sitting for a couple of weeks--or a couple of months).
@ Eric: Yeah, that's a good idea. Maybe I'll get some gasket material and a steel plate, screw it down after removing the reservoir and see what happens. "block porosity" would be a *****, huh? Or I might just replace the res gasket and try to pressure test again first. That would probably be the easiest route.

I was thinking more along something like this:

1/2" black tee-1
1/2" x 1/4" black bushing-2
30-lb pressure gauge (usually 1/4") -1
1/4" schrader valve-1
1/2" black cap-1
couple of 1/2" black steel nipples

(should be able to get all of that from a plumbing supply. (tell them your trying to make up a test rig)

looking at the coolant flow diagram.... the engine block has 2-hoses to it. one on the front of the head going to the exhaust manifold, the other on the front water pump cover going to the intake manifold.

Remove the two hoses off the manifolds (leave the other ends attached) and use them to clamp down that test rig the block and head can be tested alone together.

The exhaust manifold could be tested the same way using a couple more capped ends... looks like there's 4-antifreeze ports on the EM.

The intake manifold has 3- it looks like. (2-larger and one small)

If the 1/2" nipple is too small to fit in the hose your trying to clamp you can get an increasing coupling to a larger size pipe that would fit more snug so the hose clamp can grab onto.

Just an idea.

 

[nola mike]

Re: 470 leaking. Sigh.

Hmm, I like the thought Eric. I actually already have a rig for testing natural gas lines that would work. I could do the block first to rule out a leak there, then try the manifolds. Strange the the troubleshooting doesn't mention the reservoir itself as a potential source. I could also just kink and clamp the hoses to block off. Ugh. Hope it isn't a manifold. I'd rather do the HG than buy and source a new manifold...

 

[nola mike]

Re: 470 leaking. Sigh.

Also, forgot to mention that the mani is aluminum. And looking at that diagram I'm wondering if I'm losing some pressure to the overflow bottle during testing.

 

[nola mike]

Weird. Thought I had updated this post. Wonder if it got lost in the upgrade. Anyway, I had put in a helicoil a few years back the manifold, but it was for a 3/8" bolt by mistake instead of 7/16. The helicoil stripped out. Replaced it with the correct size. We'll see how it does today. . Finally got some alone time with the wife, will probably take a 50 mile cruise for lunch

 

[Eric 3.7LX Alpha 1]

Nice! Hope that does it

 

[nola mike]

First lunch place closed, so had to backtrack the other way. Did about 3 miles of slalom skiing, and 60-65 miles total till we found an open spot. A couple of wot runs mixed in (wife: "so now you're TRYING to break the boat?")
So far, so good...