Cooling system advice

[Plum76]

Hey all, starting to go though my list after the summer, prior to winterizing. Boat is out of the water and up at the house, so starting to look into the more significant issues, namely fuel delivery and cooling.

On the cooling side, looking for some advice on best way to clean and descale. I pulled my thermostat housing, and as I suspected, no thermostat. My cooling is a direct/freshwater system, and while it was adequate over the summer, I wouldn’t call it great. I was planning on a white vinegar soak to descale, but it’s just running out the exhaust. The inside of the housing is ugly with corrosion, though apparently unblocked. I can replace that lower section, but suspect issues deeper in the cooling jacket.

Any secret tips on how to get things cleaned out, short of pulling the whole block apart?



On a positive note, I did get my drain cock replaced without breaking the old one off in the block, and the new fuel pump is on and has suction when is spin the motor over by hand, so there’s that..

Thanks.

Jason

[uptank001]

What engine?

[Plum76]

Albin AD-21, freshwater cooled. I ended up doing a white vinegar soak, then flushed out, then a gallon on CLR once up to temp and let that sit 15 minutes, then flushed with clean water and then winterized.

Planning on ordering a thermostat before spring, hoping to smooth out the cooling function, was somewhat erratic towards end of summer, like intermittently block passages or something. I did not see a lot of debris come out, though hard to tell what's actually coming out of exhaust..

What engine?

Jason

[dkirsop]

You may have trouble finding the correct size thermostat. It needs to open at 80C. The last time I looked Albin motor only carried a thermostat for 50C which is far too cool for the AD21. Attached is a photo of my spare thermostat, it is a Wahler 01/7 80C unit. The flange diameter is 48.3mm.

Thermostat.jpeg

[Plum76]

I have seen conflicting information on temps, recommendations as low as 60c for a thermostat for freshwater cooling to prevent scale buildup, which seems quite cool for my understanding of desirable operating temps. I think I'm shooting for ~180F (or a 170-190F range) or 80C-ish range like you suggest.

My housing is sized at a 54mm thermostat unit, which is available through Albin, though at the 50C rating you suggested, which does seem too cold.

I need to spend some time at the local parts store to see what else comes up with a 54mm flange, or perhaps if nothing else, a replacement thermostat housing from Albin Motor, though I'm not seeing right off what size thermostat they are using. Two options there, bronze or cast.

What I'm hopeful of is that a thermostat will provide some closure of the bypass and force more flow through my block. It seems like the bypass is such an easy outlet, there might not be much incentive to push flow through the block, which might be part of my erratic cooling issue. I've even though about putting a slight restriction in my bypass to encourage more flow through the block, but I don't want to be running too cool, it does seem to produce much less soot at/near 180f (80c) and seems 'happy' at that temp. My system would operate happily, then creep up to ~190, then go back down in a short amount of time, really erratic for what should be a pretty consistent load on a motor..

Edit, looks like maybe a couple options here to try (from a Ferrari 308 resource of all places):

http://www.birdman308.com/service/therm ... mostat.htm

Looks like I can get a 80c (model A) and a 71C (model E) so I can have some options, and relatively cheap. Despite the '056' it seems it has a 54mm body and uses a gasket to get to a 56mm application.

You may have trouble finding the correct size thermostat. It needs to open at 80C. The last time I looked Albin motor only carried a thermostat for 50C which is far too cool for the AD21. Attached is a photo of my spare thermostat, it is a Wahler 01/7 80C unit. The flange diameter is 48.3mm.

Thermostat.jpeg

Jason

[dkirsop]

The small fluctuation you have noticed is normal. It rises and falls as the thermostat opens and closes in relation to engine temp. I expect at WOT it would display constant but at lower RPM the engine would have a greater response to the change in water flow. Interesting that the flange diameters are different; must be my closed cooling system versus your raw water system.

[Plum76]

Well, if I were running a thermostat that would be more sensical, but as my engine was without over the summer (prior owner was not running one), I'm at a loss to attribute.

The local parts store had the stant alternative to the Wahler unit, rated at 82 degrees, and for $6, figured it was worth a shot. I won't be running it until the spring, so it'll be a while before I have any results to report..

I suspect (and this is just a theory) that after a few hours of running the motor in it's insulated compartment, that it just builds up a mass of heat that is harder to cool, so over a few hours cruise, a nominally higher temp is seen, a few degrees over the start of the cruise at the same load/conditions..

JP

The small fluctuation you have noticed is normal. It rises and falls as the thermostat opens and closes in relation to engine temp. I expect at WOT it would display constant but at lower RPM the engine would have a greater response to the change in water flow. Interesting that the flange diameters are different; must be my closed cooling system versus your raw water system.

[WillieC]

My tstat (FWC) started fluctuating nominally. Then it got worse. Found 75C stat at ASAP. Price was good and it came faster than parts I have ordered stateside.

Once, some stuff I ordered got a customs charge that somebody in the chain paid just to keep my parts moving, It wasn't much so I don't think I got scammed.

I had a very hard time even finding one the correct temp, even at the "official" Volvo Penta dealer 'fiche. These engines were all originally raw water cooled and ran a 40C stat. So that's what the microfiche showed. I did not, however, make a phone call. But I know the ASAP part was about half.

New stat is rock solid, unambiguous. I know exactly how it is operating just by watching the gauge. If it doesn't open in fifteen minutes underway, I know something is amiss.

[Plum76]

I was pleasantly surprised to find one locally, much less for $6. I did ask if they had the 71 degree equivalent (this one is nominally 82C rated), just for the sake of experimentation (no joy). I'm hoping that it evens out my cooling system. In addition to the flushing I did, I will also be re-inspecting my impeller, and I replaced the raw water intake hose as well, PO had exhaust rated hose on there, so possible it was collapsing a little bit or just old and adding restriction. On my longer list is re-bedding that thru-hull and replacing/updating the valve, which may or may not be a full port valve, adding more restriction. We will see how the spring goes, at this point I'm trying to wrap up all the open jobs I have going before the weather gets too bad.

Boat was shrink wrapped over the weekend, so I'm going to reinstall my painted floor stringers and finish the fiberglass repairs from the abandoned transducers that I removed, then maybe park the boat for the winter..

JP

quote=WillieC post_id=85812 time=1602624500 user_id=4800]
My tstat (FWC) started fluctuating nominally. Then it got worse. Found 75C stat at ASAP. Price was good and it came faster than parts I have ordered stateside.

Once, some stuff I ordered got a customs charge that somebody in the chain paid just to keep my parts moving, It wasn't much so I don't think I got scammed.

I had a very hard time even finding one the correct temp, even at the "official" Volvo Penta dealer 'fiche. These engines were all originally raw water cooled and ran a 40C stat. So that's what the microfiche showed. I did not, however, make a phone call. But I know the ASAP part was about half.

New stat is rock solid, unambiguous. I know exactly how it is operating just by watching the gauge. If it doesn't open in fifteen minutes underway, I know something is amiss.
[/quote]

[dkirsop]

Assuming you have the original casting you may want to look at the exhaust elbow. This has a water jacket cast around it and extends down to where the exhaust hose connects. There is a 1/2" diameter hole inside at the bottom where the raw water discharges into the exhaust just before the hose spigot. The hole is shallow and extends just through the inner wall of the exhaust jacket. Corrosion debris can collect in this location and block the flow of water.

Clearing the rust out is a tedious job but can be done. It requires removing the elbow from the engine, soaking the manifold in the softener of your choice, making sure the exhaust is fully submerged. Then rodding out the water jacket from the inlets at the upper flange and working the material out through the lower hole or loosening material at the upper end and shaking it out through the flange ports.

Use a 1/2" drill to clear the lower discharge hole before starting. It is accessible through the exhaust pipe spigot.

Once done consider soaking the exhaust in a bath of rust inhibitor to slow further accumulation . This is probably a once in 5 year task provided you flush your engine with a corrosion inhibitor such as Salt Away at the end of each season. I know you do not boat in salt water but this product incorporates a corrosion inhibitor as well.

[dkirsop]

One other note. The ports in the elbow flange are redundant as the mating manifold flange is blind. I expect the ports were provided specifically to assist in removing accumulated corrosion scale.

[Plum76]

This is good info, seems like it’s worth doing as I’m not sure the last time (if ever) that it has been done. Motor only has 466hrs, but not sure of rebuild extent at the time, would like to think it was thorough, but you know..

JP

Assuming you have the original casting you may want to look at the exhaust elbow. This has a water jacket cast around it and extends down to where the exhaust hose connects. There is a 1/2" diameter hole inside at the bottom where the raw water discharges into the exhaust just before the hose spigot. The hole is shallow and extends just through the inner wall of the exhaust jacket. Corrosion debris can collect in this location and block the flow of water.

Clearing the rust out is a tedious job but can be done. It requires removing the elbow from the engine, soaking the manifold in the softener of your choice, making sure the exhaust is fully submerged. Then rodding out the water jacket from the inlets at the upper flange and working the material out through the lower hole or loosening material at the upper end and shaking it out through the flange ports.

Use a 1/2" drill to clear the lower discharge hole before starting. It is accessible through the exhaust pipe spigot.

Once done consider soaking the exhaust in a bath of rust inhibitor to slow further accumulation . This is probably a once in 5 year task provided you flush your engine with a corrosion inhibitor such as Salt Away at the end of each season. I know you do not boat in salt water but this product incorporates a corrosion inhibitor as well.

[Plum76]

Minor update, the Stant unit does not fit my housing, it hits the top of the housing prior to seating, so no go.

JP

I was pleasantly surprised to find one locally, much less for $6. I did ask if they had the 71 degree equivalent (this one is nominally 82C rated), just for the sake of experimentation (no joy).

[Plum76]

So this turned out to be pretty prophetic advice. I pulled the exhaust manifold and exhaust and had a look. I found chunks of the raw water impeller that munched itself earlier in the summer, three pretty good sized ones.



These were stuck near the bottom outlet on the manifold, certainly impeding flow. Will sort out how to best remove whatever corrosion I can reach, but at least nice to find something obvious, wonder how many other bits of that impeller are in the rest of the system?

The engine side of the equation:



Jason

One other note. The ports in the elbow flange are redundant as the mating manifold flange is blind. I expect the ports were provided specifically to assist in removing accumulated corrosion scale.

[dkirsop]

There is clearly some significant differences between your engine - raw water cooled, and my engine - closed cooling system. I noticed your thermostat housing looks different from mine too.