need help with aux coolant pump, WVO trick - PeachParts Mercedes-Benz Forum

Mistel · #1 02-20-2006, 08:24 PM

I am starting a WVO conversion on an 85 300tdt and I read about this tip/trick on Frybrid's site. It is about the aux coolant pump

The fix is to make sure the aux coolant pump is working properly. On 300's MB added a small coolant circulation pump to help with coolant flow though the heater at low speed. Fixing this pump (with one that actually works) and wiring it into +IGN will dramatically increase the amount of coolant that flows though the system.
"The pump is normally on when there is vacuum (vacuum switch) and the climate control thermostat is calling for heat. If this pump is hooked up to +IGN so it comes on with the ignition, it will help with cirtulation though the whole system all the time."

As I am a newbie to working on my Benz, I am looking for advice on how to do this trick, such as where could I hook-up the pump to +ign? Fusebox? would I have empty fuses that are +ign that I could use? Not afraid of a little wiring.

Thanks

Peter

rwthomas1 · #2 02-20-2006, 09:47 PM

Pick a circuit under the hood that is ignition switched. Unplug the aux pump and wire the ground to ground then run the hot side to a relay with a fuse. Drive/trigger the relay with the ignition switched ciruit. Very easy. I don't know how well this works in the stock location but I am guessing that adding an additional aux pump to the WVO heater lines and wiring as I have described would work even better. This way the stock aux pump can do its things as designed and the WVO system has a dedicated pump. I suppose this all depends on where the coolant feed/return is hooked up on the cooling system. RT

Mistel · #3 02-20-2006, 10:14 PM

RT

Thanks for the response. Maybe I should just do what you suggest, get a second Aux coolant pump and plumb it into the wvo circuit, wired to +ign.

Hmm.. Thinking...

Does the stock aux cool.pump restrict the flow of coolant if it is not running I.E. in the summer? would I then have my WVO aux cool.pump trying to pump in a closed circuit? Winter or summer, I would need the coolant in the WVO circuit to flow

Also, since I have manual windows, manual sunroof, do I have free circuits on my fuseblock that are already wired +ign, where I could just stick a fuse in and run a wire?

That's why I love these forums, new idea's!

Peter

sailor15015 · #4 02-20-2006, 10:33 PM

I would think that, in its stock position, having it run all the time would make no difference since the monovalve has to be open for it to be able to pull anything out of the engine, through the core, pump, then back to the radiator, if I'm remembering the path correctly. In the setup I have, there are two t-connectors, one between the engine outlet and the heater core, the other after the core but right before the aux pump. This setup bypasses the monovalve and allows coolant to flow out of the engine no matter what setting the CCU is on. This works great for me but most of my driving on veggie is highway. I suppose if you weren't running the heater, and doing a lot of stop and go driving, you could add an extra pump to improve flow. I actually did this for a time but I didn't see that much of an improvement. If you want to wire it to be on all the time, look in your fuse box and pull a few fuses until you see a tiny screw hole. There should be several throughout the box. Use a voltmeter to see which hole is on when the key is on. Good luck finding a screw to fit that hole. Mine came with one and that's what gave me the idea to hook the signal wire to my veg heater relay to it so it would be on all the time that the key is on, instead of just when I flip the switch. Good luck.

Mistel · #5 02-20-2006, 10:47 PM

Thanks Seth

Being in Ontario Canada, I want all the heat for my WVO I can get. I am starting to like the idea of a second aux pump.

Peter

sailor15015 · #6 02-20-2006, 11:09 PM

Heat is most definately your friend. I have a copper coil in the tank, glow plug heater before the filter, and a VegTherm heater right before the ip. Any local McParts store should have a generic pump. I went to the same store twice before I found someone who knew what I was talking about. If I remember correctly it only cost around $30.

#7 02-21-2006, 05:21 PM

I use an aux water pump for cylcing the water in my intecooler and it runs whenever the car is on. The pump doesn't mind one bit.

BTW the stock aux water pump shuts off when the heater is selected off...so it only runs when the monovalve is somewhat or fully open...never when closed.

black280ce · #8 02-21-2006, 09:50 PM

Can someone post a pic of the aux water pump?

thx