Hi Guys.
New member to the forum here, struggling with an ongoing issue that I am hopefully someone may be able to shed some light on.
When I am running my engine at temperature and under load (say 3 or 4 thousand RPM), then I come off of plane I have a situation where coolant overflows from my heat exchanger and into my reservoir. This I would think would be normal as pressure builds up in the engine and cooling system, however, the issue is that the engine continually dumps the coolant into the reservoir until it is full, then eventually the reservoir exits coolant through it's overflow into the bilge. This process continues for approximately an hour until coolant has completely exited the engine and heat exchanger, resulting in an eventual overheating situation. Adding more coolant/water to the top of the radiator stops the overheating, however, it is only temporary until the pressure is built back up and the system exits the new coolant to the reservoir. Once the engine cools, coolant never seems to return to the heat exchanger either, which I find perplexing.
Things to note:
- The engine seems to run very well once warm, however, does run a bit rough at cold start requiring me to keep the RPM at 1k to keep running. Slight smoke is present from the exhaust at cold start (smells rich though not sweet to me).
- The engine is a pretty newly rebuilt motor from a machine shop (a year old), so I would be surprised if the head gasket was going, although symptoms I realize might suggest this. With that said, the new engine may have been running slightly hotter then normal operating temperatures due to exhaust flappers having deteriorated and sitting in the exit of the exhaust which was found when replacing the impeller.
- Which leads me to mentioning that I have replaced the impeller in the Alpha one leg and can confirm that the raw water flow is strong.
- With the engine cold, I have pressurized the cooling system and it holds pressure without any issues.
- While the engine is overflowing coolant I do not have overheating, only once the coolant has exited the engine and heat exchanger does it start to overheat.
- The rad cap was replaced and appears to be sealing well.
I purchased a combustion tester from the auto parts store (the type which you connect to your rad/heat exchanger and it looks for exhaust gasses in your coolant) ie: http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm. I tried to test this yesterday, however, it asks that you connect the other end of the tester to a vacuum hose so that it can pull the fumes from the coolant and I don't believe that this engine has vacuum lines? Perhaps I am wrong is there vacuum lines? If so where?! Assuming I am right, any other suggestions in terms of how I could do the test? Maybe bring a hoover down and rig it up to it to create vacuum? Obviously I am trying to determine if there is a head gasket issue here.
Outside of exhaust fumes pressurizing the coolant (bad head gasket), what else could be causing this problem? I have not removed the heat exchanger, and some people have suggested that the heat exchanger could be faulty and pressurizing the system some how? Others have suggested that mercruiser put out a bulletin which suggested the impeller in the alpha one did not supply a strong enough flow of raw water and that they recommended adding a belt driven raw water pump as well?- This would make sense if it was a boil over issue, but it seems like a pressure issue to me?!
Any other ideas as to what it could be would be greatly appreciated. I am wits end here and I don't know what else to consider...
Thanks all.
New member to the forum here, struggling with an ongoing issue that I am hopefully someone may be able to shed some light on.
When I am running my engine at temperature and under load (say 3 or 4 thousand RPM), then I come off of plane I have a situation where coolant overflows from my heat exchanger and into my reservoir. This I would think would be normal as pressure builds up in the engine and cooling system, however, the issue is that the engine continually dumps the coolant into the reservoir until it is full, then eventually the reservoir exits coolant through it's overflow into the bilge. This process continues for approximately an hour until coolant has completely exited the engine and heat exchanger, resulting in an eventual overheating situation. Adding more coolant/water to the top of the radiator stops the overheating, however, it is only temporary until the pressure is built back up and the system exits the new coolant to the reservoir. Once the engine cools, coolant never seems to return to the heat exchanger either, which I find perplexing.
Things to note:
- The engine seems to run very well once warm, however, does run a bit rough at cold start requiring me to keep the RPM at 1k to keep running. Slight smoke is present from the exhaust at cold start (smells rich though not sweet to me).
- The engine is a pretty newly rebuilt motor from a machine shop (a year old), so I would be surprised if the head gasket was going, although symptoms I realize might suggest this. With that said, the new engine may have been running slightly hotter then normal operating temperatures due to exhaust flappers having deteriorated and sitting in the exit of the exhaust which was found when replacing the impeller.
- Which leads me to mentioning that I have replaced the impeller in the Alpha one leg and can confirm that the raw water flow is strong.
- With the engine cold, I have pressurized the cooling system and it holds pressure without any issues.
- While the engine is overflowing coolant I do not have overheating, only once the coolant has exited the engine and heat exchanger does it start to overheat.
- The rad cap was replaced and appears to be sealing well.
I purchased a combustion tester from the auto parts store (the type which you connect to your rad/heat exchanger and it looks for exhaust gasses in your coolant) ie: http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm. I tried to test this yesterday, however, it asks that you connect the other end of the tester to a vacuum hose so that it can pull the fumes from the coolant and I don't believe that this engine has vacuum lines? Perhaps I am wrong is there vacuum lines? If so where?! Assuming I am right, any other suggestions in terms of how I could do the test? Maybe bring a hoover down and rig it up to it to create vacuum? Obviously I am trying to determine if there is a head gasket issue here.
Outside of exhaust fumes pressurizing the coolant (bad head gasket), what else could be causing this problem? I have not removed the heat exchanger, and some people have suggested that the heat exchanger could be faulty and pressurizing the system some how? Others have suggested that mercruiser put out a bulletin which suggested the impeller in the alpha one did not supply a strong enough flow of raw water and that they recommended adding a belt driven raw water pump as well?- This would make sense if it was a boil over issue, but it seems like a pressure issue to me?!
Any other ideas as to what it could be would be greatly appreciated. I am wits end here and I don't know what else to consider...
Thanks all.
