Heat exchanger end cap

[Richit]

I was changing the zinc in the heat exchanger and some broke off inside. To clean it out of the exchanger, I wanted to remove the cap at the end of the exchanger and wasn't sure how to remove it after I removed the bolt. It hasn't been removed for a couple of years and is solidly on there. I didn't want to pry it loose with a screwdriver for fear of damaging the gasket or bending the cap. I also was concerned about trying to use a large vice grip to pull it off. Any suggestions?

 

[Jeff652]

Personally, I would pry it off. The cap itself is relatively sturdy and unlikely to break. You will have to sacrifice the gasket so have another on hand when you put it back on.

 

[Stu Jackson]

Jeff's right, but pry carefully. Much depends on how much of the zinc you "lost" to be able to clean it out that way. If it's just a little, it may not even be worth it.

If it's a lot, I recommend you take the whole HX off. I also read "rod the tubes out" and find that oft-repeated mantra to be useless. If you've been using the engine, the inside of the tubes will usually be very clean because the water rushes through the thin diameter tubes very fast.

What I DO find is a build-up of salt on one of the inlet ports, if you're in salt water. My original HX had it built-up so much that half of the port was blocked.

 

[SG]

Speaking form personal experience (with a lot of hours on our Yanmar with plenty of water flow of both antifreeze on one side and saltwater on the other) -- the rodding-in out may not actually clean-out the heat exchanger. It may look clean, but it actually can have a "scum" on it which reduces the heat transfer.

I'd be careful using acid because some heat exchanger parts are aluminum.

The best way to clean a heat exchanger, form my experience is to remove it and send it to an automotive radiator shop. They have large ultrasound cleaners that will remove all build-up whether visible or not. Usually, by the next day .

 

[Richit]

Thanks all. Normally, the water temp runs at a steady 165, so I think I have good flow. But I've failed to remove all the zinc before, and have had water flow impacted to raise the temp by 10-15 degrees - and the culprit was the end of the zinc. So, I want to open it to verify that a chunk of zinc isn't moving around or blocking the flow. I'll try first to open the cap, then decide if the whole HX needs cleaning. Either way, I'll need to get the cap off. It was cleaned out and acid washed about 4 years ago. I'll let you know what happens.