Hi all!
Taking over my old man's sailboat and A4 engine maintenance is new to me. I've been spending hours reviewing and reading forum posts, this web site is the bomb.
We have a late model A4 with FWC. Years ago the raw water strainer was removed and never replaced. Engine hasn't seen a lot of use over the last 5 years or so, maybe 20 hours combined.
Engine began overheating during a sailing trip up the eastern shore (NS, Canada). Steam from the engine compartment as the coolant boiled over (we don't have a overflow/recovery bottle, it just dumps to bilge). A healthy amount of raw water still ejecting with the exhaust but we still double checked the sea water intake valve, raw water impeller, and hosing up to heat exchanger. Due to lack of strainer we then found and removed a healthy clump of seaweed salad in the raw water access port on the heat exchanger, but this didn't resolve the issue.
I believe the issue lies somewhere with the cooling system. The coolant ran dry but I believe this was due to boiling over but could a coolant leak be possible?
Here are the things that come to mind but I need help to figure out if I'm on point, missing anything, and what order of operations make sense:
- Blockage in the seawater tubes of the heat exchanger? We poked around with a narrow screwdriver but didn't find much.
- Thermostat blockage or failure?
- Coolant pump blockage or failure? (Is there some way to visualize whether coolant is flowing through the lines?)
- Manifold blockage? (Am I even correct that the manifold is the rectangular box right next to the block where coolant flows from the tstat housing to the manifold then to the heat exchanger?)
- could a downstream blockage in the exhaust cause the overheating conditions as described? Again, getting healthy amount of sea water exiting out the back
As far as order of operations, I'm thinking to first remove and asses tstat and clamp bypass line to gauge whether full coolant flow through engine solves problem.
Then, open up coolant pump to see if any blockage in impeller.
Then, check manifold output for blockage.
Then, somehow blow out heat exchanger?
What am I missing...
Any and all advice welcome.
Regards,
Dave C.
Taking over my old man's sailboat and A4 engine maintenance is new to me. I've been spending hours reviewing and reading forum posts, this web site is the bomb.
We have a late model A4 with FWC. Years ago the raw water strainer was removed and never replaced. Engine hasn't seen a lot of use over the last 5 years or so, maybe 20 hours combined.
Engine began overheating during a sailing trip up the eastern shore (NS, Canada). Steam from the engine compartment as the coolant boiled over (we don't have a overflow/recovery bottle, it just dumps to bilge). A healthy amount of raw water still ejecting with the exhaust but we still double checked the sea water intake valve, raw water impeller, and hosing up to heat exchanger. Due to lack of strainer we then found and removed a healthy clump of seaweed salad in the raw water access port on the heat exchanger, but this didn't resolve the issue.
I believe the issue lies somewhere with the cooling system. The coolant ran dry but I believe this was due to boiling over but could a coolant leak be possible?
Here are the things that come to mind but I need help to figure out if I'm on point, missing anything, and what order of operations make sense:
- Blockage in the seawater tubes of the heat exchanger? We poked around with a narrow screwdriver but didn't find much.
- Thermostat blockage or failure?
- Coolant pump blockage or failure? (Is there some way to visualize whether coolant is flowing through the lines?)
- Manifold blockage? (Am I even correct that the manifold is the rectangular box right next to the block where coolant flows from the tstat housing to the manifold then to the heat exchanger?)
- could a downstream blockage in the exhaust cause the overheating conditions as described? Again, getting healthy amount of sea water exiting out the back
As far as order of operations, I'm thinking to first remove and asses tstat and clamp bypass line to gauge whether full coolant flow through engine solves problem.
Then, open up coolant pump to see if any blockage in impeller.
Then, check manifold output for blockage.
Then, somehow blow out heat exchanger?
What am I missing...
Any and all advice welcome.
Regards,
Dave C.
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