What pressure to test coolant system?

[prof_mariner]

I ran the engine this morning. The air temp was in the low 60's F and it was calm. I idled the engine out of the marina and then slowly brought the engine RPM's up to 1,000, then 1,200, then 1,500, then 1,800, then 2,000... and that was the extent of the throttles range. That surprised me because I expected it to go to 3,000+/- rpms. When I bought this boat the previous owner replaced the stock alternator with a big 100 amp, single wire alternator, leaving the tachometer disconnected. When I fixed that, I -assumed- the tach readings would be correct. I turned on a gps and it showed I was going 8 knots! So first lesson I learned was that the tach is off, probably by 500 - 1,000 rpms!

I also smelt burning plastic and started to see steam (I'm sure it was steam) coming out of the exhaust. No way to check the temp of the exhaust water but when I checked the raw water strainer (it's the plastic type with the clear top) it was sucking air! Since I wasn't able to see the top of the strainer before (because it was directly under the galley sink, I had to assume that if water was coming out the exhaust, it was working. I now know better.

I also watched the engine water temp gauge and it stayed at a steady 70 degrees Celsius until I kicked up the rpms to full throttle, and then it rose to around 85 degrees Celsius.

When I got back to the slip, I checked the exhaust water temp while the engine was idling and it was warm, and there wasn't any steam in the exhaust. The engine is still hot so can't check the coolant level yet. I checked the raw water pump and the impeller looks fine (although I'll change it and the gasket anyways).

At this point (and unless the coolant level has dropped) I'm thinking it's either the raw water strainer is leaking air and/or the intake strainer is blocked.

[belizesailor]

Sucking air. Maybe a vaccum leak down stream of the raw water pump that needs high RPM vaccum to become an issue? A hose that collapses at high vaccum? ...

[prof_mariner]

Originally Posted by belizesailor

Sucking air. Maybe a vaccum leak down stream of the raw water pump that needs high RPM vaccum to become an issue? A hose that collapses at high vaccum? ...

The raw water strainer is between the pump and the intake through hull. I've had one of these strainers before and after a while the gasket deforms and getting a good seal is next to impossible. I'm going to check the intake to make sure it's clear and then replace the strainer.

[prof_mariner]

I'm beginning to think I may have found the problem.

I opened the raw water pump and although the old impeller looked fine I replaced it anyways. Then I opened the raw water strainer and the gasket (if you can even call it that) was dried out and badly cracked. I cleaned it out and sealed it temporarily with Vaseline. Then I ran the engine and gave it a test. Big improvement and as I increase the throttle, the volume of intake water increases accordingly. Great. Tomorrow I'm off to buy either a new gasket for the strainer or a whole new strainer. Then I'll give it a final test. Incidentally, I'm not really seeing any change to the coolant level. Fingers crossed this was the only problem.

[W3GAC]

Coolant leak tests are usually done at about 15-17 psi... no more than 20 psi. Leaks can be temperature dependent... only when engine is cold or only when hot at normal running temp, or, the easiest to find... when not temp dependent and leak either cold or hot. No need to run the engine while testing... just get it up to temp, shut down engine, and pressurize it... being careful when removing cap of hot engine (might just already have test cap on before running up temp. FYI- getting engine up to running temp at dock may be harder than you think to do since our engines without good load may not come up the operating temp with cooler Winter water temps.

If your gauge holds within 1-2 psi starting at say 15 psi for an hour or so at cold and then at hot engine condition... likely not a leak.

But give us more info:
- Are you losing coolant? How much in 8 hours of run time or some other time frame?

- Are you seeing white smoke at start-up?

- Are you smelling 'sweet' antifreeze smell in engine area/ or exhaust?

- is your oil showing any signs of contamination (bubbles, milky, thick mud)?

- Is a crew member drinking it? (Just kidding)

- Have you tasted it? OK, serious now. If you have a breach in the heat exchanger, raw salt water can mix/ dilute the coolant in the engine coolant loop. It doesn't take much salt water contamination to taste it. Don't drink it! Just dip your finger in the coolant at your 3-4 psi cap area and touch your finger to end/top of your tongue where salty taste buds are most dense/ sensitive. Move tongue around a bit like your a tasting a good wine. Whether you taste it or not, finish up by rising out mouth with fresh water/ wipe tongue on clean cloth/ paper town... maybe drink a little of that good wine, a coke, or rinse w/ mouthwash to erase any after taste. A salt taste means you'll need a new or rebuilt heat exchanger. Fortunately your Perkins has been a popular engine in marine for a long time and you'll have many options to chose.


Sometimes the level in the coolant expansion/ auto-fill reservoir constantly needs topping off. I'm talking about the small (usually plastic tank that has a small 1/4 - 3/8 hose going from that tank to very near the fill cap on engine. Often that small hose fails right at either end/ hose clamp that's been cutting into it/ over tightened and coolant (but not coolant actually in the engine loop) is slowly weeped out and evaporates as it hits the hot engine/ or in the hot engine compartment area. Replace hose/ clamps.

Failing head gasket is another ugly possibility and white smoke at start-up and hard starting or irregular/ rough engine running initially (low compression on one cylinder) are usual signs (along with disappearing coolant w/ o other explanations). Do a cylinder by cylinder compression test to check for compression health on each cylinder. At this point you are getting near the professional mechanic level of experience/ tools. A good diesel mechanic while pricey has much experience and can get to your issue pretty fast with the right tools/ experience. Don't be surprised if he redoes/ doesn't just accept your test results. That just how they are and something you didn't notice during the tests nay be the give-away clue of the leak problem./ solution.

Good luck. Let us know what you find.


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[belizesailor]

Originally Posted by prof_mariner

I'm beginning to think I may have found the problem.

I opened the raw water pump and although the old impeller looked fine I replaced it anyways. Then I opened the raw water strainer and the gasket (if you can even call it that) was dried out and badly cracked. I cleaned it out and sealed it temporarily with Vaseline. Then I ran the engine and gave it a test. Big improvement and as I increase the throttle, the volume of intake water increases accordingly. Great. Tomorrow I'm off to buy either a new gasket for the strainer or a whole new strainer. Then I'll give it a final test. Incidentally, I'm not really seeing any change to the coolant level. Fingers crossed this was the only problem.

Sounds like a potential winner to me. Easy fix so hopefully so.

[prof_mariner]

Coolant leak tests are usually done at about 15-17 psi... no more than 20 psi. Leaks can be temperature dependent... only when engine is cold or only when hot at normal running temp, or, the easiest to find... when not temp dependent and leak either cold or hot. No need to run the engine while testing... just get it up to temp, shut down engine, and pressurize it... being careful when removing cap of hot engine (might just already have test cap on before running up temp. FYI- getting engine up to running temp at dock may be harder than you think to do since our engines without good load may not come up the operating temp with cooler Winter water temps.

I'll give this a try, thanks.

If your gauge holds within 1-2 psi starting at say 15 psi for an hour or so at cold and then at hot engine condition... likely not a leak.

Good to know.

But give us more info:
- Are you losing coolant? How much in 8 hours of run time or some other time frame?

I've not been able to run it that long yet and only have been able to see the coolant level since yesterday when I removed the galley counters and sink. But so far, no, I haven't seen any coolant leaking.

- Are you seeing white smoke at start-up?

No.

- Are you smelling 'sweet' antifreeze smell in engine area/ or exhaust?

No.

- is your oil showing any signs of contamination (bubbles, milky, thick mud)?

No.

- Is a crew member drinking it? (Just kidding)

Not that I'm aware of...

- Have you tasted it? OK, serious now. If you have a breach in the heat exchanger, raw salt water can mix/ dilute the coolant in the engine coolant loop. It doesn't take much salt water contamination to taste it. Don't drink it! Just dip your finger in the coolant at your 3-4 psi cap area and touch your finger to end/top of your tongue where salty taste buds are most dense/ sensitive. Move tongue around a bit like your a tasting a good wine. Whether you taste it or not, finish up by rising out mouth with fresh water/ wipe tongue on clean cloth/ paper town... maybe drink a little of that good wine, a coke, or rinse w/ mouthwash to erase any after taste. A salt taste means you'll need a new or rebuilt heat exchanger. Fortunately your Perkins has been a popular engine in marine for a long time and you'll have many options to chose.

Not sure that I'm going to try that, although if you're in the San Diego area and want to give my coolant a taste, you're welcome to it.

Sometimes the level in the coolant expansion/ auto-fill reservoir constantly needs topping off. I'm talking about the small (usually plastic tank that has a small 1/4 - 3/8 hose going from that tank to very near the fill cap on engine. Often that small hose fails right at either end/ hose clamp that's been cutting into it/ over tightened and coolant (but not coolant actually in the engine loop) is slowly weeped out and evaporates as it hits the hot engine/ or in the hot engine compartment area. Replace hose/ clamps.

With the galley cabinets gone I can see pretty much every inch of the engine and it's plumbing. No leaks anywhere that I can see.

Failing head gasket is another ugly possibility and white smoke at start-up and hard starting or irregular/ rough engine running initially (low compression on one cylinder) are usual signs (along with disappearing coolant w/ o other explanations). Do a cylinder by cylinder compression test to check for compression health on each cylinder. At this point you are getting near the professional mechanic level of experience/ tools. A good diesel mechanic while pricey has much experience and can get to your issue pretty fast with the right tools/ experience. Don't be surprised if he redoes/ doesn't just accept your test results. That just how they are and something you didn't notice during the tests nay be the give-away clue of the leak problem./ solution.

Before I could see what was going on I really thought I had a blown head gasket / cracked head. But now that I can see what's going on, and after a cylinder by cylinder compression test, I'm pretty sure the head is solid.

Good luck. Let us know what you find.

I will. I'm posting this thread in the hopes that it will help others who may run into similar symptoms in the future. Engine over heating seems to be the bane of sailboat owners, I know of 3 other boats in this marina that are all having something fixed related to engine over heating.

[W3GAC]

Great! It does sound very likely that the dried gasket could be the root of your issue. Hope it works out with tomorrow's final test.


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[prof_mariner]

Well I think I'm close to calling this a success. I temporarily sealed the leaks in the raw water strainer (it's a Vetus 150 which nobody seems to sell anymore) using an o-ring, gaskets I fabricated from neoprene gasket material and a liberal amount of vaseline.

Gave the cooling system a pressure test while it was still cold and it held 15 psi no problem. Then I ran the engine under a moderate load until it got up to operating temp (about 70 degrees C). Checked the exhaust water and it was cool, not warm. Stopped the engine and attached the cooling system tester but had a hard time getting it to seal properly. It took a couple tries but it finally sealed and it held 15 psi just fine. Tomorrow will be the full load test. Fingers crossed that test goes well.

[W3GAC]

Congrats! Sounds like you can put this problem/ solution in the log as a success. (I'm not expert on Vaseline but believe its water soluble. Might want to consider silicon grease to lube gasket . Many sources and uses (zipper lube, head lube, waterproofing coax fittings, and available at West Marine, Radio Shack, most hardware stores. )


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[prof_mariner]

SUCCESS!!! I primed the raw water strainer and gave the engine a good workout this morning. Ran the engine hard at about 90% throttle for several miles. Engine temp rose to 78 degrees celcius (the spec'd temp for the thermostat) and stayed there. No steam or white smoke in the exhaust. All fluids where they should be. Boy am I happy.

I did find that the raw water strainer still leaks (my temporary gasket isn't going to cut it) and I also have a small leak at the vented loop, so I still have some work to do. But at least now I know what the problem is and it's relatively cheap and easy to fix.

Thanks everyone for your help.

[belizesailor]

Congrats!