Just starting the conversion on my Mercedes 190d.... I've got 3/8" od PEX fuel line inside 5/8" heater hose for my HIH. There's a 3/8" copper heat exchanger in the 2nd tank and 3/8" coiled heat exchanger around the veggie oil filter. I can run the garden hose through the whole deal no problem. The system is t'ed at the intake to the heater core (just behind the oil filter near the firewall) and returning just before the electric aux coolant pump. It should all work great, but it doesn't! I had the same setup in my old rabbit, and it worked flawlessly. It seems I'm not getting much coolant flow from this Mercedes. With the hoses off, Almost none at all at idle a decent flow at about 1500 rpm, but not much pressure behind it. I even wired the aux coolant pump to run all the time, and it's still not running the coolant through the system. All the air is out. Why don't I have enough pressure to feed through my HIH/ heat exchanger setup???????? drove it 100 miles, and the hih setup is cool as a cucumber.... heater works. '85 190d 2.2. Thanks in advance!

Just a oouple thoughts...

1. Is it possible that you actually T'd in on the wrong side of the heater core?

2. Sooner or later you may want to consider a metal line in the interior of the HIH. There have been some reports of PEX not being quite up to the task over the long haul.

Good luck.

Charlie

I had to install an auxillary pump on my veggie system on my benz, my food service salesman had to install one on his too. I hear reports of people having great success without the pump but I haven't had any luck yet. I even had a new water pump on my benz and it still wouldn't push the coolant throught the veggie system. I didn't have a problem with mine running down the road but in town going slow or idling behind the pizza shop it would cool right down to nothing.

It can be reall PITA to burp the air from the cooling system of the 616 and 617 engine. I bet that is the problem.

Go to http://www.mercedesshop.com/shopforum/forumdisplay.php?f=15 and do a search using "burping, burp, Coolant, hose" Use the fill in box that says something like not all words have to be present.

I have heard it's a pain to get a Benz to flow, so I put in a FPHE and used full sized 5/8" hose to feed it. It flows well, but the length of hose to and from is pretty short, not all the way to the tank and back like yours.

You could install somewhere in there at a high point a temporary RV water pump? Once it all seems to be working right take the pump out. Then you only got that small amount of air from removing the pump to deal with?

Pizzaman, Where is the MB aux. water pump in the system anyway?

OK... spent the day messing with this problem. The fix was one of 2 things. I installed bigger fittings on my HIH tees so more coolant would flow. (3/4" instead of 1/2") then gave the whole system a reverse "enema" with a garden hose hooked up at the input side of the SVO heating system. I let the hose run with the reservoir cap off until all the gurgling stopped. I suspect it was an air in the lines problem all along, more-so than the new fittings, but it can't hurt. Thanks for all the replies. If it wasn't for this forum and others like it, I would have never tried these coversions.

now I got mostly water in my cooling system.... thank goodness it's summer! gotta pull out that old anti-freeze tester to see. where the heck did I put that....

Jeep,
I put it on the end of the vegoil system where the coolant would be coldest. Just before the t back into the coolant system at the water pump.

John,

Would you be able to post photos or schematics of the conversion on your 190D? I'm getting ready to convert my 1984 190D 2.2, and I'd love to see what you came up with.

Thanks,
Jason

I had a very similar problem getting my coolant to flow nice and hot all the way back to my veggie tank in the trunk. I installed a 12 volt RV aux. water pump in the trunk and I have a switch to turn it on on the dash. When the car is heated up and i've been running the pump, the fittings in the trunk are hot to the touch! This is with 20 feet of hose to the trunk and 20 back to the tee into the coolant line. so it's a long stretch, the l in sdl stands for long wheel base! My car is looooooooong. This has worked extremely well for getting very hot coolant all the way back there. otherwise the coolant will take the path of least resistance through the heater core or straight into the radiator and never even think about making the trip bake to my trunk.