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Discussion Starter · #1 ·
Greetings to all. While I have regularly changed the coolant on my 1989 PSC 34 without incident (except for a leaky petcock), I have wondered about the coil of clear plastic hose that goes to a ball valve in the water heater circuit in the port cockpit locker. Since this seems to be a standard arrangement it occurs to me that I might be missing something if I don't do something with it. I generally add coolant to the expansion tank in the same locker.

I might add a note of thanks to all those who have posted in the six or seven years that I have had this boat and sought out your collective wisdom, which has been quite useful and appreciated.
 

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We have a 1987 PSC 34 and the only valve in the port cockpit locker is to bleed air from the coolant catch tank. Maybe you could post a photo?
Steve
 

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Discussion Starter · #3 ·
Thank you for the response. I am confident the valve and hose is there for bleeding air from the system but what has puzzled me is why it it is (a) coiled and screwed to the back side of the dish compartment, and (b) needed given that the header tank for the water heater can serve the same function. However, it occurs to me that uncoiling the hose can get the fill (or bleed) point well above the highest point in the water heater so perhaps the idea is to add coolant when the hose is uncoiled and elevated as a means to assure that there are no air pockets down the line. Does that sound right?

On a related note, the plastic Yanmar expansion tank for my Yanmar 3HM35f has never functioned as might be expected (i.e., the fluid level has not increased when the engine is hot, nor decreased as it cools), presumably owing to a cracked braze at the top of the header tank in the port cockpit locker. Meanwhile, the engine has worked fine without sufficient coolant pressure to engage the expansion tank (a mechanic once suggested I leave the cap on the header tank loose). Anyhow, a local radiator shop recently repaired the header tank and suggested that I use a 7 psi cap rather than the 13 psi cap specified by Yanmar. (This may reflect the shop's lack of confidence in the repair, which was soldered rather than brazed.) Now, with a 7 psi cap on the header tank and the original Yanmar cap on the heat exchanger, the fluid level in the plastic expansion tank is on the rise, going from the low (cool) mark to near the very top of the tank after about 4 hours of running. This suggests that the Yanmar cap opens at less than 7 psi, and that there could be a problem on the cooling (i.e., sucking) side. I will get my various radiator caps (Yanmar stock, 7 psi, and 13 psi) tested, but am now curious as to what pressure caps work on PSC 34s that still have water heaters in the port cockpit locker. I might add that I have not filled the upper, header tank above half way.

In short, do PSC 34s typically use 13 psi caps on both heat exchanger and header tank or use caps with different pressure ratings (presumably higher on the header tank), and does the Yanmar expansion tank typically function as intended on boats with water heaters?

Thank you for your patience with this rather long-winded discussion. Any insights will be much appreciated.
 

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deisher6
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Hey GriffonPNW: Our PS 34 has a similar set up as you describe without the coil of hose. There is a coolant tank in the port cockpit locker with a pressure cap and an expansion tank on port side of the engine compartment. The fluid level in the expansion tank does not change much as the engine operates. We still have the suitcase looking water heater mounted aft of the engine compartment on the port side. Engine runs fine. Though like you I have wondered about the lack of expansion.

regards charlie
PS34 Windrunner
 

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I have pressure caps on my engine and on the metal high point tank in the port cockpit locker. The service manual gives the specification of the engine cap as
139211

The expansion tank cap is marked 13 lbs. Rubber tubing from each is combined in a tee then continues to the plastic expansion tank in the engine compartment. The level in the plastic expansion tank rises and falls a little as the engine heats and cools. The metal high point tank is under vacuum when I open it cold. If I open the engine cap, I make a total mess as the coolant pours out. I opened the bleed valve in the port cockpit locker once filling the coiled hose with coolant. I wired the valve shut. The coolant is still there. My engine coolant goes to a bus heater under the starboard settee that we use in the winter then to the water heater in the port cockpit locker before returning to the engine. In the summer a three way valve bypasses the bus heater and keeps the hot coolant out of the cabin. On occasion, I have moved coolant from the plastic expansion tank to the metal high point tank when the expansion tank has become too full.

Bill Murdoch
1988 PSC 34
Irish Eyes
 

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Discussion Starter · #6 ·
I have pressure caps on my engine and on the metal high point tank in the port cockpit locker. The service manual gives the specification of the engine cap as
View attachment 139211
The expansion tank cap is marked 13 lbs. Rubber tubing from each is combined in a tee then continues to the plastic expansion tank in the engine compartment. The level in the plastic expansion tank rises and falls a little as the engine heats and cools. The metal high point tank is under vacuum when I open it cold. If I open the engine cap, I make a total mess as the coolant pours out. I opened the bleed valve in the port cockpit locker once filling the coiled hose with coolant. I wired the valve shut. The coolant is still there. My engine coolant goes to a bus heater under the starboard settee that we use in the winter then to the water heater in the port cockpit locker before returning to the engine. In the summer a three way valve bypasses the bus heater and keeps the hot coolant out of the cabin. On occasion, I have moved coolant from the plastic expansion tank to the metal high point tank when the expansion tank has become too full.

Bill Murdoch
1988 PSC 34
Irish Eyes
 

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Discussion Starter · #7 ·
Thanks to each of you for your very helpful responses. Bill M's set-up makes sense and seems like a good solution. My boat has the tubing from the heat exchanger going to the Yanmar expansion tank (plastic) and the tubing from the header tank going to the bilge, which makes little sense if both pressure caps are rated the same. The advice that I received from the radiator shop to put a 7 psi cap on the header tank obviously messes with the system, but for the time being seems to be working. (I only fill the header tank about half way in hopes that it will bleed air rather than coolant.) It is my understanding that each pound of pressure raises the boiling point about 3 degrees, so even 7 psi may be helpful. I suppose I could put the 7 psi cap on the heat exchanger but then I'd wonder whether the expansion tank would fill to overflowing, and as Bill indicated changing engine caps makes a mess (the heat exchanger being lower in the system). I recently checked the side of the header tank using an infrared thermometer and got about 175 degrees, under load at 2400 rpm, which seems reasonable.

As to the coiled hose in the cockpit locker, when I replaced the coolant last week I uncoiled it to make a new high place in the system, which I thought might help purge air pockets, and then blew into the hose to move the coolant level back to the bleed valve, which I shut so little or nothing was left in the hose.

Anyhow, Bill's mention of a bus heater is intriguing. We often run our propane bulkhead heater when underway, even using the engine, and a bus heater would certainly be more efficient. So, not meaning to stray off topic, I'm curious as to where it is mounted.

Thanks again, Rick
 

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Our heater is a 40,000 BTU Heater Craft 500 Pro bought from Defender in 2014. It is mounted under the starboard settee right in the middle. A 4" hole drilled between compartment under the forward part of the nav desk and the area under the settee lets cold air return to the heater. (On our boat the locker under the nav desk has a louvered door.)

139239


Bill Murdoch
1988 PSC 34
Irish Eyes
 
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