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OVerheating Engine, Part 2

Hey John,
Some S/B Chevy motors have been known to have an occasional problem with core shift.The water jacket sand release eyebrow is a little too close to the head gasket/cylinder. When the conditions are right a small amount of combustion gas will blow a minor amount of coolant out the overflow, but just until the coolant level is low enough to let just the excess combustion gases vent.
When this happened to me the engine wasn't really overheating badly but was blowing out a little coolant occasionally. I pulled the heads to have some porting done, the head shop noticed where the head gasket was leaking, they welded the head and surfaced it. I put it back together and no more leak!

Good luck
 
John, your test shows that there is a rise in pressure while running, and it certainly could be a result of what Chris is suggesting. But is this alone enough to cause this one cylinder bank to show such an increase in temperature???

In a closed system, the circ pump will mildly charge the engine block! This is what allows the thermostat to release coolant on demand or as needed.
This would be baring no cylinder pressure leaks (head gasket), and yet no pressure increase due to heat expansion!

Any pressure from the circulating pump (the GM pump) I'd think would be a zero-sum-gain because of the suction side.
IOW, if it's suspect that the circ pump is creating the pressure that you are seeing, the other side of the circ pump should balance this out.
In theory, that is.
You yourself mentioned that the pressure remained after shut down.

What if you were to test the other engine for a comparison?????

I'm beginning to think that your ultimate solution will be removing that one cylinder head and then further test and check things out as per Chris.
Once removed and opened up, then perhaps look into the cooling jackets (both block and head casting) with a very high end but small bore scope.
I'd also examine the front circ pump port as well as the circ pump itself.

Don't forget to ask yourself the "Chicken or Egg" question.... in that which lead to which?
IOW, is a failing head gasket the result of restricted cooling on this one bank (????)...... or is this increased cylinder bank temperature a result of a head gasket issue???


One other note re; not running a thermostat, is that we ideally want to keep engine temps to around 160/180, so I'm still looking at the No Stat as a temporary band aid fix.... as I'm sure you are also.
 
RicardoMarine said:
John, your test shows that there is a rise in pressure while running, and it certainly could be a result of what Chris is suggesting. But is this alone enough to cause this one cylinder bank to show such an increase in temperature???
Click to expand...

If the rise in pressure (Compression leak) is creating an air pocket, it would definitely cause a hot spot.
 
Docksidemarineservices said:
If the rise in pressure (Compression leak) is creating an air pocket, it would definitely cause a hot spot.
Click to expand...
I don't disagree, Chris. What you describe could certainly cause hot spots.
But if this is great enough to cause over-heating on this bank, why isn't coolant being puked out all over the place... or have I missed reading that?
 
RicardoMarine said:
I don't disagree, Chris. What you describe could certainly cause hot spots.
But if this is great enough to cause over-heating on this bank, why isn't coolant being puked out all over the place... or have I missed reading that?
Click to expand...

Rick,

I think you have answered this yourself already:

RicardoMarine said:
I'm still looking at the No Stat as a temporary band aid fix.... as I'm sure you are also.
Click to expand...
 
RicardoMarine said:
I don't disagree, Chris. What you describe could certainly cause hot spots.
But if this is great enough to cause over-heating on this bank, why isn't coolant being puked out all over the place... or have I missed reading that?
Click to expand...

Looks like he has a possible initial start compression leak, after a few minutes of running the leak is minimized due to heat expansion. It's not overheating the whole bank of cylinders it is just causing a hot spot where the intake meets the head on the cross over triggering the over heat alarm.
 
Bob, are you suggesting that the No Stat (in a closed system) would prevent a head gasket pressure leak from showing up as excessive coolant side presssure and coolant puking?
Just curious.

I don't know what the exact answer is at this point...., but I think it's past time to pull that cylinder head off.

Chris, understood and it makes sense to a degree (no pun intended). :D
 
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Rick,

No, I just think it's altering the normal operation, (ie; temperatures, pressures, circulation), and effecting the results of the experiment.
 
RicardoMarine said:
What say we all purchase airfare, and meet in Cabos to further discuss this???? :D I could use a vacation anyway.
Click to expand...

Ha! Ha! Ha! :cool:

I was going to suggest the same! Only, my idea was a stealth mission in which we slip aboard at night, I was concerned about our night vision gear getting bumped around in the engine room. I'll bring the gasket set and the tools, if someone else can bring a cyl head (just in case), and the doughnuts.
 
Reverend Bob said:
Ha! Ha! Ha! :cool:

I was going to suggest the same! Only, my idea was a stealth mission in which we slip aboard at night, I was concerned about our night vision gear getting bumped around in the engine room. I'll bring the gasket set and the tools, if someone else can bring a cyl head (just in case), and the doughnuts.
Click to expand...

Can we do this after I return from St Maarten next week?
 
OK guys. I agree the head needs to come off my overheating port engine, it is the "what's next" part that concerns me. So the plan (up until yesterday, I will get to that in a moment), was to continue to gently run the boat until Feb. 27 (that is when my brother in law leaves from his week long visit). As I have mentioned, if one plans his trips there is no reason to exceed trolling speed as we can start fishing when we leave the marina. The engine seems stable at these speeds (say under 2100) and pressure is low. I need to be in Phoenix again mid Feb. for a day, so I will pick up a gasket set and a torque wrench. I will do the air pressure test to try and isolate the leak, and I will pull the head on the 27th of Feb. If it is only a gasket I reassemble. I plan to go back to Florida in the first week of March so if it is more than a gasket I go back to the states, find parts sources and order and have shipped to Mexico. I will be back in Cabo for all of May and will fix it then. That's the plan.

Yesterday coming into port we developed a problem in the other engine....a knocking sound that definitely should not be there. So until that is resolved, no more boating. And if it turns out I need to have the marina mechanic (the $75/hr. guy that speaks no English) pull that motor then that may change my wait until the end of Feb. plan for the starboard engine. Isn't boating fun?

I am starting a separate thread on the starboard engine. I hope some of you can quickly tell me what might be going on there.

As for coming down, I have two extra bedrooms.

Thanks again.

CaboJohn
 
I am not sure if anyone is still reading this thread, but I will give an update. My boat partner had guest coming to Mexico and wanted the boat usable, so I left in early March without pulling the motor apart. I will return in May and do the job then. So at this point I still do not know what I will find. I will first do a compression test and then do Chris's leak test by pressurizing the cylinders to see which one is leaking into the coolant. Questions: I am assuming that if it just appears to be a head gasket failure I should have the head milled flat before reinstalling. Or should one first put the head on granite and check it for flatness with a feeler gage? If so, how flat should it be? What is a typical stateside cost for milling (everything is negotiable in Mexico but I need to know what is reasonable)? Do I need to (or should) remove the valves first?


As for my other thread about the rattling noise in the other engine: Getting the engine to run smoothly has greatly reduced the rattle, but not eliminated it. I would very much like to peek at the flex plate, but don't find any sort of access port in the bell housing. Is there one there? (92 Crusader, 5.7 liter Captain's Choice). I understand that on some boats there is room to pull the transmission and bell housing and get at the flex plate without pulling the engine. Has anyone tried this on a Pursuit 3000 or do I need to have the yard pull everything out to get to the problem?


Thanks for any advice.


CaboJohn
 
If you pull it, I'd get it magnafluxed to ensure its integrity. Flatness - 0.0039" across the head, on the head gasket surface, checked three ways: 1) down the middle, 2) diagonally, 3) opposite diagonal from 2).

Two options for the flex plate inspection. if you have a timing plug, it will be on the flywheel cover, unter the heat exchanger. The other (less useful) option if to remove the inspection cover (front of flywheel, behind oil pan). ideally, a small borescope helps. a good light and a small mechanic's mirror may provide a viable alternative.
 
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