7.4 Coolant Issue


WhatsTheFormula

WhatsTheFormula

New member
I recently bought an SS with twin 7.4L. I noticed my coolant was lower on both sides and that the reservoirs seemed a little dirty too, like there was some old coolant in there for awhile. I took off the reservoirs and cleaned them well. I took off the hoses to the reservoirs and also cleaned them. Then filled with Merc 50/50 premix to the neck on the heat exchangers and added some to the reservoirs as well. The Starboard side engine looks to be just fine, but the port side does not. Anyone have any ideas? Almost looks like water in the reservoir.. Could be a crack in my heat exchanger?

Starboard side:
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Port side:
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Since you have a closed cooling system your next step would be to drain the coolant and do a cooling system pressure test. There is a special Heat Exchanger cap that you can buy (automotive) to do the test. You want to see if the cooling system holds 15 psi of pressure without leaking down.
 
The easiest thing to do rite now would be to check your heat exchanger end seals out. On the exchanger you have a rubber gasket on each end that seals the unit up. They almost always leak internally, you also will loose antifreeze when they go bad. Its super easy and inexpensive to check and do, take the end cap off both sides of the engines heat exchanger your having problems with and that rubber frisbee sealing it on there is what I am talking about.. The parts are like 10 bucks and should only take you a few minutes to do. If that seal looks like something out of a horror flick, then that's probably your problem. Replace them on both engines if they look nasty, your anti freeze can leak out and sea water can get in when these fail. Super easy to do and inexpensive but very common for them to fail, start with the easy stuff first. :cool:
 
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Here a pic of a good one, around 10bucks on ebay for a pair.
 
Excuse my ignorance.. im still learning. How do these allow sea water to get into the internal system? When looking at the exchanger it seems as if these are just caps at the end that keep the sea water from leaking out of the ends of the exchanger? Wouldn't there need to be a crack in the tubes inside the exchanger for the sea water and internal system to mix?
 
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