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Main Message Board / Re: Disappearing coolant
« on: January 14, 2022, 07:06:05 PM »
Point of information for everyone (actually two POIs.)
A leaking Hx is basically a throwaway item. Yes it can *sometimes* be fixed but is typically not worth the cost. OEMs were typically not copper-nickle (more expensive) and more prone to pin-holing (between the seawater and engine coolant sides) esp in saltwater. Coolant doesn’t end up in the bilge (it goes out the exhaust) so it’s hard to diagnose w/o pressure testing the Hx.
A leaking WH (again, typically a pinhole between the potable water vessel and coolant tube) typically does NOT lose engine coolant - it GAINS engine coolant. Why? The closed engine-coolant loop maxs out about 15 psi, and the hot water vessel is nominally at whatever pressure your potable water pump is set at (much higher than the engine pressure.) So coolant can’t push against that high pressure and get into the potable water side (good thing cuz it’s toxic, so BEWARE if your potable water is unpressurized.) The WH pressure can actually go much higher than the engine block*** (why the WH tank has a temp/pressure relief valve) so potable water can move in the opposite direction, sometimes with coolant ending up in the bilge or wherever the coolant reservoir bottle can overflow to (potable water pushes into the WH hoses, to the engine block, out the exhaust manifold pressure cap, to the coolant reservoir overflow.)
*** Why the check valve on the WH must be rated for WH use, and not the plastic ShurFlo CVs that are typically used on potable water lines. They can blow up (and ruin your day.)
A leaking Hx is basically a throwaway item. Yes it can *sometimes* be fixed but is typically not worth the cost. OEMs were typically not copper-nickle (more expensive) and more prone to pin-holing (between the seawater and engine coolant sides) esp in saltwater. Coolant doesn’t end up in the bilge (it goes out the exhaust) so it’s hard to diagnose w/o pressure testing the Hx.
A leaking WH (again, typically a pinhole between the potable water vessel and coolant tube) typically does NOT lose engine coolant - it GAINS engine coolant. Why? The closed engine-coolant loop maxs out about 15 psi, and the hot water vessel is nominally at whatever pressure your potable water pump is set at (much higher than the engine pressure.) So coolant can’t push against that high pressure and get into the potable water side (good thing cuz it’s toxic, so BEWARE if your potable water is unpressurized.) The WH pressure can actually go much higher than the engine block*** (why the WH tank has a temp/pressure relief valve) so potable water can move in the opposite direction, sometimes with coolant ending up in the bilge or wherever the coolant reservoir bottle can overflow to (potable water pushes into the WH hoses, to the engine block, out the exhaust manifold pressure cap, to the coolant reservoir overflow.)
*** Why the check valve on the WH must be rated for WH use, and not the plastic ShurFlo CVs that are typically used on potable water lines. They can blow up (and ruin your day.)
but understand that the first A engines that Wb produced (25XPA/3-20A/35A, etc.) were in March 1993 (source TOAD universal model history which info I’d imagine came from Wb?) Before then (1990-1993) I’d guess that Wb was still turning out “non A” Universals??