DreamstateSeven
New Member
- Jul 15, 2019
- 8
- Boat Info
- 1990 Sundancer 270
- Engines
- 7.4L Mercruiser Bravo 1
Hi CSRs! Been lurking on here for a while, and this community has already helped me figure out a bunch of stuff for my 1990 270 DA and 1980 260 DA. But now the 1990 7.4 L Mercruiser is having a strange coolant issue that has me stumped.
When the engine runs up to temp, the coolant recovery bottle fills up and starts to overflow into the bilge. I've probably drained about 5 liters of what looks like diluted coolant. Even when the engine cools, it doesn't drain back into the heat exchanger.
The engine sits nicely at temperature, even for extended higher-RPM runs (around 3,000), so there's no signs of overheating.
I've tried pouring coolant back into the heat exchanger, and it fills up, but then it drains very slowly. I've confirmed that coolant is not leaking from anywhere else in the system, so it's going -- somewhere from the heat exchanger.
Current working theory is that I might have a tiny leak in the heat exchanger coil, so sea water is mixing with the coolant, causing the recovery bottle to overflow -- but allowing the engine to still be kept cool. And that when I manually fill it back up, the coolant is escaping into that leak.
I've ordered a new pressure cap for the heat exchanger to see if it helps. Next step is going to be to use an infrared temperature tool to shoot different parts of the block and make sure that it is being consistently cooled.
Just trying to see if anyone has any other thoughts or advice! I'm feeling like the heat exchanger might be at the end of its life, but I'd really like to narrow it down. It's an expensive replacement part, so I wanna be sure!
Thanks all!
When the engine runs up to temp, the coolant recovery bottle fills up and starts to overflow into the bilge. I've probably drained about 5 liters of what looks like diluted coolant. Even when the engine cools, it doesn't drain back into the heat exchanger.
The engine sits nicely at temperature, even for extended higher-RPM runs (around 3,000), so there's no signs of overheating.
I've tried pouring coolant back into the heat exchanger, and it fills up, but then it drains very slowly. I've confirmed that coolant is not leaking from anywhere else in the system, so it's going -- somewhere from the heat exchanger.
Current working theory is that I might have a tiny leak in the heat exchanger coil, so sea water is mixing with the coolant, causing the recovery bottle to overflow -- but allowing the engine to still be kept cool. And that when I manually fill it back up, the coolant is escaping into that leak.
I've ordered a new pressure cap for the heat exchanger to see if it helps. Next step is going to be to use an infrared temperature tool to shoot different parts of the block and make sure that it is being consistently cooled.
Just trying to see if anyone has any other thoughts or advice! I'm feeling like the heat exchanger might be at the end of its life, but I'd really like to narrow it down. It's an expensive replacement part, so I wanna be sure!
Thanks all!
