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Comments
Just before i realized the manifold was broken again I moved the boat to the end of the dock and back to my slip to pump out. Upon arriving back I discovered the broken manifold side riser was cold where the 3 other manifold risers without problems was warm. Does this suggest anything to anyone?
@212rowboat
@Alswagg
the pipe inside a pipe exchanges the heat with the water jacket, warming the water jacket and the reason sealed manifolds get warm... when the jacket is busted, the water puts the heat source out and the heated water and exhaust spits out the exhaust at higher RPM and floods the engine at lower...
you said long block, right? so... new heads... did you check the heads on a flat to see if the surface was true?
you may want to consider the mighty remflex gasket if you have to replace the manifold (obviously, you do). they will seal up any imperfections.
I went through the entire water system again last night, there is no obstructions. The cylinder head must be damaged.
head issues could be that it is out of flat, either the decks or the ports.
the springs could be wrong, the rockers could be wrong, the valves could be wrong, the seats could be wrong, the seals.
i hate to repeat this- but a vacuum gauge will tell you everything you need to know about the head, even if you have an exhaust leak or an intake leak.
Surely there must be a check valve somewhere to stop the manifold water draining when the engine is at rest. 212rowboat or Alswagg will know.
Even though the water flow is good, if the manifold is draining backward somehow, when the hot engine is off, the manifold will heat soak, and possibly fracture when the flow is resumed. Has it ever fractured when the engine is started from cold? Are the fractures all at the top end?
BTW, for those who missed it. Massive flash flood damage in/near Houghton, MI on Sunday. This is in the north tip of the UP in Mich.
PC BYC, Holland, MI
Something has to be hiding and overlooked, for it to follow to a different engine seems very strange!?
"I recently replaced the long block on the starboard side as well and the problem persisted"
are the gaskets the right ones? there seems to be a huge selection of those things, and it's dang easy to use the wrong ones.
I am suspicious of the check valve being stuck at first. However I want to say it was stuck open, should there be a spring in that valve? If i blow decently thru the bottom of the valve it closes off, it seems that with any water pressure it would float up and close off the entry to the manifold. I have been researching this valve tying to understand its proper function.
So I finally gave up with the "pros" and took this back into my own hands. I really got deep into this and learned the water system inside out. Here is what i discovered.
This motor has what is called a single point drain system, part of this system is a series of check valves, you have a main one on the rear of the engine that is spring loaded and that unit opens via pressure from the raw water pump and closes via the spring when the engine is off. Next up are two ball valves that are located on the bottom of each of the manifolds, these have a floating plastic ball that is supposed to float up and reduce flow going up into the manifold from the bottom port. These valves are designed as a tee, with water coming up through the bottom via a distribution manifold near the front of the motor. The water comes from that manifold and travels into the floating ball valve which is suppose to restrict two much flow from going straight out the manifold so the rest of the cooling system gets adequate pressure and flow. The other leg of the tee is above the the ball valve and is fed off the thermostat housing.
I recently discovered something in common that had been overlooked, it seems the manifold was cracking only when cruising at idle for extended periods of time. I made several long distance trips that did not start or end with a lengthy wake speed travel. After making this realization i went back to the cooling system, determined there there must be something wrong. I decided to pull the hose from the tee on the manifold that is fed from the thermostat housing and fire the engine up. I expected to see flow from both of those hoses, since they are fed from the thermostat housing they should always have full flow to the manifold. What i discovered was not what i expected, i had very little water coming from those hoses, some but not quite what i expected. What i did not expect was to see the port side of the motor (good manifold) flowing a full force jet out of the t valve, the broken side occasionally spitting water. Continued below
Well my mind starts racing, what is going on here. Could this matter or not? The tee on top from the thermostat housing should be providing cooling water still to the manifold. Surely this wouldn't cause a problem would it, or would it..
Lets dive deeper, i am suspect I am cracking manifolds at low rpm wake speeds, what happens when we are low rpm. The water pressure drops from the high of 11psi to around .9-1psi. We are getting very little flow at that point, but now i have a ball valve on one side that is completely shutting off water flow to the manifold that and the other side is stuck wide open allowing all the water to flow straight out that side unrestricted.
Remember, water just as electricity will take the path of least resistance. Now i feel like I'm on to something, I need to replace or remove this single point drain system valves and ensure i have equal water to each of the manifold at low speeds when we are not getting high psi from the water pumps.
So i decided to order a 5th manifold and gasket set. I get ready to install it but I'm not taking any chances here. What else could be wrong. I grab the 3" riser, if i had low flow could this be damaged? There are 4 water cooling passages, one on each side flowing up out the top holes on each side. How is this cooled? Just the water passing on the sides? I buy some plugs and plug two holes on the top and blow into one of the holes and discover i get a faint hint of air leaking into the other hole. I can hear the tone change as i put my finger over the hole on the opposite side. So.... do these riser have a cooling passage internally to flow water from one side to the other ultimately cooling the sides of the riser? I start trying to find out, so i call the "pros" again, 2 shops tell me absolutely not, there is not a cooling passage but how can i be hearing air to the other side, your not he said. That is solid cast. So i drive over to one of them and show them, i am indeed hearing this. He picks up his phone and calls a Mercruiser engineer he knows, this guy knows everything. He says no, confirming what the "pro" told me. I still don't believe it, he says its cracked inside the metal from one side to the other but not through into the exhaust. I don't hear air leaking into the exhaust but I'm not buying this is cracked. I think there is a water passage in it. I look with a borescope, it is heavily corroded and i see what i believe to be a water passage but it appears corroded completely shut. I call the real pro, @Alswagg and ask him. He had never heard of anyone replacing one and have never checked one himself but he was convinced there has to be a water jacket that cools the sides of the riser, that is straight fire shooting up through there. Continued
That brings me to today, i just finished redoing the water system, i decided to get rid of that crappy tee valves and put back the original drain plug style, i connect the 2 lines off the distribution manifold together instead of capping them off and take the manifold cooling lines off the thermostat housing direct to the manifold port. Now, we must flow the water through the engine and there is no where for the pressure or flow to escape without it being evenly distributed.
Both manifolds have full flow to them, the riser is nice and cool on all 4 sides, the engine is not getting water into the manifold and it SOUNDS EXACTLY LIKE THE GOOD MOTOR. I also discovered that rpms came way up, last time i put a new manifold on i was able to get from the low rpms of 3600 to 4600. Will this be the END OF THIS SAGA? It took 6 "pro" attempts, thousands upon thousands of dollars from me and replaced every part on the engine before I discovered a fundamental basic flaw. If we are cracking the manifold, should'nt your very first go to be to 100% verify proper water flow at all times while understanding how the system works. 5 manifold before this, and not once did a "pro" shop do any diagnostics, not once did they verify the flow, not once did they check or investigate the cooling passages which led me to looking at the riser and ultimately discovering it was bad.
In wrapping up, i suspect this is the end of this saga, i suspect that i have always had a small crack in the exhaust manifold for the last 4 years, the ball valves finally become so bad that one was stuck wide open and one was stuck fully closed. The manifold could no longer take the heat and we opened up the small crack flooding the engine and hydrolocking it, the pros replaced several manifolds and reinstalled the bad valves and riser. We went into a instant cycle until i took over and started diagnosing the problem the pros only cared to sell me parts that i did not need, charge me $100 per hour to install these parts and then pick the next target part they wanted to replace.
This is not a bash on full time shops, but I was taken pretty bad by them. Some are better then others. I just can’t understabd how you could physically take 2 broken parts off the old manifold and install them on the new manifold and not once check them to see if they are broken.
I feel really good about it being solved, Im praying it to be so, what say you?
2007 300 EC, 350 Mags, B3's, Table Rock Lake, MO