Cooling system questions - PeachParts Mercedes-Benz Forum

polarisrmk · #1 02-11-2011, 10:33 PM

I currently have a project where i am putting a 617.952 into a boat. I am working on the cooling system and have a few questions to discuss. I am thinking about getting rid of the pressurized mercedes expansion tank from the cooling system and using a filler neck like the one in the picture in the return line from my heat exchanger to the thermostat housing. then i would just use a radiator cap and a conventional overflow bottle. Thoughts? suggestions?

BimmerBenz · #2 02-12-2011, 12:01 AM

Yup, no problem.

The Gears · #3 02-12-2011, 02:56 AM

You still have to keep a pressure on the system. Why not just mount the MB tank on the bulk head. Fill as in the car.

polarisrmk · #4 02-12-2011, 10:30 AM

Quote:

Originally Posted by The Gears

You still have to keep a pressure on the system. Why not just mount the MB tank on the bulk head. Fill as in the car.

Would my plan not still keep pressure in the system? last I checked it would.....radiator cap just wouldn't have a tank under it. I don't want to use the mb tank for several reasons the major reason is there is not much room in the engine compartment and I am having trouble fitting all the fittings in required to hook the mb tank up. The heat exchanger does not have provisions for hooking up the tank like an mb radiator does so all connections have to be made externally. The second reason is it's quite ugly with all the hoses and fittings. I would like a much cleaner look

The Gears · #5 02-13-2011, 02:24 PM

Don,t forget about expansion of the cooling fluid. It has to go somewhere.
Any kind of tank of sufficient size can be "teed" into a line. It also has to keep some pressure, about 1 bar same as in the car. Use the same cap.

polarisrmk · #6 02-13-2011, 02:54 PM

Quote:

Originally Posted by The Gears

Don,t forget about expansion of the cooling fluid. It has to go somewhere.
Any kind of tank of sufficient size can be "teed" into a line. It also has to keep some pressure, about 1 bar same as in the car. Use the same cap.

I was going to used a unpressurized expansion tank ...

josha37 · #7 02-13-2011, 03:31 PM

You will be totally fine, plently of cars use radiator caps on parts of the system other than the radiator. Fab on!

The Gears · #8 02-13-2011, 05:36 PM

Think about what happens when you loose the pressure on your car. the cooling system usually boils over. If you can run sufficient water through the heat exchanger you may be ok. I have a 671 GM diesel in my boat.
Neither the seawater side nor the fresh water side are under pressure.
The heat exchanger acts as the expansion tank. I fill it to the brim and let it spill over on the first run, then leave this as the correct fresh water level. Don't forget about anti freeze.
How will you pump sea water through the heat exchanger, and at what volume.

babymog · #9 02-13-2011, 06:01 PM

The system will be fine, pressure held by the cap, un-pressurized overflow tank to contain expansion water, you'll be fine.

Gears: On your 6-71, it needs to be pressurized, and needs the proper SCAs or you'll find cavitaion pitting through your cylinder walls. Wet-sleeve engines (especially 71 DD) are very sensitive to coolant quality, surface tension, nitrates, pH, etcetera. It should have a pressure cap on the glycol side.

The Gears · #10 02-13-2011, 06:10 PM

Babymog.
Up on the coolant stuff, Use GM marine dealer supplied for 15 years and all ok so far.
Thanks for concern. As for the cap I guess it may be spring loaded and there is a drain tube going down to the bilge.

polarisrmk · #11 02-14-2011, 12:08 AM

Quote:

Originally Posted by The Gears

Babymog.
Up on the coolant stuff, Use GM marine dealer supplied for 15 years and all ok so far.
Thanks for concern. As for the cap I guess it may be spring loaded and there is a drain tube going down to the bilge.

it will work just like any car with an unpressurized expansion tank. the system will still have pressure ~1 bar there is a fitting on the side of that radiator cap adapter for an expansion tank. not quit sure you are understanding what the rest of us are saying.

The sea water will be coming from the normal pickup at normal volume for an engine with a closed cooling system. The boat has an Alpha 1 (gen 1) on it with the pump mounted to the top of the lower unit. I have already done tests to make sure the cooling is adequate.