Head port question on '83 300SD - PeachParts Mercedes-Benz Forum

PNO TECH · #1 12-02-2005, 10:16 AM

Hah! Got your attention, didn’t I?

What I wish to inquire about is not grinding on the head, but rather the advisability /practicality of plumbing into the coolant system at one of the ‘ports’ on the driver’s side of the head of a 617 95x. They are between the glow plugs. The one near the oil filter housing has a heater hose going to the aux. pump, the second forward seems to have a temp sensor in it, and the one just above the IP looks perfect to tap into for heating my planned two-tank WVO conversion. I can’t access Braingears or Skinnerbox from my work computer so I don’t know how the flow goes in there but if it won’t mess up the MB cooling design, it looks like a great place to tap for a heat exchange. Thoughts, advice, warnings are appreciated.

I want to preheat my blend for now, and have decided on coolant rather than electric heat. I plan to return the coolant to the system after the aux. pump.

Scot

#2 12-02-2005, 10:26 AM

I believe you are talking about the return line from the heater core to the engine. That line will only have flow when the heat is on, and the coolant will have already been cooled somewhat. It doesn't sound like the best location.

PNO TECH · #3 12-02-2005, 10:37 AM

The diagram I got from a WVO heating post on this forum seems to show the flow from the head to the "heat exchanger" thru a "regulating valve for vehicle heater" so I am assuming that is to the heater core. I'm looking for the 'get hottest quickest', and the port near the IP looks like it would be a straight shot out instead of messing with the doubled-over hose behind the oilfilter tower.

sailor15015 · #4 12-02-2005, 11:17 AM

The diagram I got from Neoteric Biofuels was crap. Here's the best solution I've come up with. On the driver's side, where it comes out of the block and goes to the heater core, put a T fitting and run it where you will. This will be your supply side. Plumb the return in right before the aux pump, where the metal line turns to rubber. This way you bypass the monovalve and don't have to have the heat on to circulate coolant. It works great and the cabin heat isn't affected and the tank warms right up. PM me if you still have questions and I'll take some photos for you.

#5 12-02-2005, 11:18 AM

Quote:

Originally Posted by PNO TECH

The diagram I got from a WVO heating post on this forum seems to show the flow from the head to the "heat exchanger" thru a "regulating valve for vehicle heater" so I am assuming that is to the heater core. I'm looking for the 'get hottest quickest', and the port near the IP looks like it would be a straight shot out instead of messing with the doubled-over hose behind the oilfilter tower.

I think you're correct, I just looked at the diagram and at my car. I looks like the line from the drivers side of the head is the supply to the heater core and the other line with the monovalve and the aux. pump is the return to the engine. I always thought it went the other way, but I guess not.

It sounds like your plan is reasonable if you are talking about a relatively small line. I would be concerned if you installed a large bypass and reduced the amount of coolant getting to the heater core. I would connect the return line between the aux. pump and the engine because (I think) the pump only runs when the heat is on. I doubt it would effect engine cooling if its a small flow.

Pete Burton · #6 12-02-2005, 11:26 AM

you can probably take it off there, but you'll be robbing the heat to your cabin somewhat. I doubt it'll hurt anything, that head is pretty tough. I have another thought though. Consider the vacuum switch fitting on top of the thermostat housing. It inhibits the opening of the EGR when the engine is cold. Since coolant starts to flow by this area when the thermostat opens, you could tap straight into this. Flow would automatically begin when engine is up to temp.

PNO TECH · #7 12-02-2005, 11:30 AM

Thanks, Seth, I will. Right now I gotta go earn my keep.

PNO TECH · #8 12-02-2005, 05:47 PM

Quote:Consider the vacuum switch fitting on top of the thermostat housing. It inhibits the opening of the EGR when the engine is cold. Since coolant starts to flow by this area when the thermostat opens, you could tap straight into this. Flow would automatically begin when engine is up to temp.

I thought about that, but, 1) I want to keep the install as simple and 'clean' as possible-and the 'port' I'm talking about is already at the IP (where I need the most heat) 2) IF I understand correctly, the aux pump circulates coolant from the head whether or not the thermostat is open; hence my "hottest quickest" remark.

Am I making sense? More importantly, is the above right?

Thanks,
Scot

#9 12-02-2005, 06:27 PM

Quote:

Originally Posted by PNO TECH

2) IF I understand correctly, the aux pump circulates coolant from the head whether or not the thermostat is open; hence my "hottest quickest" remark.

On my 300D, the aux. pump only runs when the heat is on. You may want to check your car.

t walgamuth · #10 12-03-2005, 01:16 AM

he was talking of an extra port in the head on the drivers side that is simply plugged. if so that seems ideal to me as it wouldnt interfere with anything else, then perhaps return in to the heater return line or a t in the rad hose.

by the way, craig, would it be better to insulate this line or not? (sly aside about the turbo insulating post).

tom w

Elktonjohn · #11 12-03-2005, 01:32 AM

interested lurker requests pics...don't yet see where you want to tap in but will check it out tomorrow and have the same concerns/issues...in need of the best place to tap heat for vo. I've got an 83 SD and don't THINK it's got an aux heat pump...can't find it. Personally I figured there had to be a logical place, easy to find for easy heat exchange but man I don't know...it's not like my Father's Oldsmobile....please continue....

#12 12-03-2005, 03:05 AM

Quote:

Originally Posted by Elktonjohn

interested lurker requests pics...don't yet see where you want to tap in but will check it out tomorrow and have the same concerns/issues...in need of the best place to tap heat for vo. I've got an 83 SD and don't THINK it's got an aux heat pump...can't find it. Personally I figured there had to be a logical place, easy to find for easy heat exchange but man I don't know...it's not like my Father's Oldsmobile....please continue....

Your aux pump is between the two firewalls deep below the mass of hoses next to the top of the monovalve.

All of us w126 bodies have one

TonyFromWestOz · #13 12-03-2005, 12:19 PM

The most accessible locations to tap into the coolant system for providing heat to a Used Cooking Oil (UCO) fuel system, is to cut a Tee into the vertical part of the hose coming from the head, near the oil filter. Be careful how you route the hoses, to avoid issues when changing the oil filter. The return coolant Tee can be cut into the hose going to the water pump on the other side of the engine.

The water pump on these engines is strong enough to circulate the coolant through a fully open thermostat, into the radiator and back to the engine. Even with the thermostat fully open, the water pump has plenty of pressure available to circulate coolant through the heater core AND any parallel fuel heating system, even if constructed of coolant hose of the same diameter as the heater circuit.

PNO TECH · #14 12-03-2005, 01:39 PM

[QUOTE=TonyFromWestOz]The most accessible locations to tap into the coolant system for providing heat to a Used Cooking Oil (UCO) fuel system, is to cut a Tee into the vertical part of the hose coming from the head, near the oil filter. Be careful how you route the hoses, to avoid issues when changing the oil filter. The return coolant Tee can be cut into the hose going to the water pump on the other side of the engine.

Thank you, sir. Thats the design I had settled on, but I want to try to tap in closer to the IP and avoid that little curly hose; its tight over there! Just trying to tweak it and make it 'mine', I guess. I'm looking for hard data on whether it is safe to pull coolant from there.

Thank you all for the input.
Scot