Hello,

I have owned a 1992 300SD for 18 months that was converted to run on veg oil. It has done well for 12,000 miles. Last week the alternator went out an got it rebuilt. During that time, I also noted that the car was running hot. It is 105 degrees in Salt Lake right now.

Anyways, I got the car back yesterday and it is accelerating poorly. It did not do this before I got the alterator changed. Seems unrelated? Also I put a half tank of B20 in the car to see how it would run about 1 week ago. Could the fuel filter be clogged and could that explain the slow acceleration and loss of power going up hills.

Thank you

Chinu

Yep.

Hey,'

I have read many of you suggestions in the past and greatly apprecitate your input. Could there be anything else causing this problem?

Also, I had the cooling system checked but the car still seems to run hot. The radiator cap was changed (no rubber seal) but no significant difference noted. Any ideas?

Thanks

Chinu

There could be a dozen things causing this problem. But, the fuel filter is the simplest task and the first place to start. Stating every possible source of low power for climbing grades in a W-140 will take most of the day.

If you're going to tackle the problem yourself, the filter is the first place to begin.

Ok,

I'll start with the fuel filter.

Chinu

If the filters check out...

Check that all the vacuum hoses behind the right headlight are connected as they should be. The ECU uses vacuum actuators to enable boost. If there's no vacuum to close the wastegate, default is full open and effectively no turbo.

IIRC there's no way to replace the alternator from below. You have to remove the turbo air intake hose and pull the alternator through the gap. Very easy to hit the vacuum hoses behind the headlight in the process.

Sixto
87 300D

Hey Sixto,

Enjoyed reading your conversion of the 3.5 to the 3.0. hope it works well.
Your explanation would explain the temporal relation of the loss of power to the changing of the alternator. I will have the mechanic who did the work look at those specific connections.

Thank you

Chinu

Hey,

The fuel filter was ok. Sixto you were right, one of the vacuum lines got unplugged. It was an easy fix. Thanks for the advice.

Couple of questions. Should the fuel filter be changed more often than the 30,000 miles that the manual says since I am running it on biodiesel and WVO.

Also, it is 100 + degrees here in Salt Lake and the car runs between 80-100 C on the temp gauage even sometimes higher going up a steep grade. Is this nomal for the heat or should I get it checked out. I had to have the radiator cap replaced but the cooling fans and the water pump seems to be ok.

Thanks again,

Chinu

I would consider 100c normal for 105f outside. There's a product called Be Cool, in what looks like an old oil can, that cuts a few degrees off the water temp. 92c is nominal for these cars.

With a clean block, MB label coolant and a 606 11 blade fan and clutch as recommended by speedy300turbo, my 93 SD 3.0 would stay under 90*C unless pushed really hard. Even at WOT in fourth up the Sunol and Altamont grades in the SF east bay it didn't cross 100*C. Ambient was never more than 90*F before its demise so I don't know how it would have fared idling on hot days. And I always have AC running.

What's the point? A 603 in a 140 is capable of running cooler unless there's something inherently hot about a 3.5. FWIW the 3.5 would idle close to 100*C on 100*F days but it had a dead clutch.

If you see 100*C while idling with the AC off, I'd be concerned.

Sixto
87 300D

I wouldn't go 30K miles on a fuel filter. I'd rather throw away a clean filter than a dirty filter, if you know what I mean.

How does the clear filter look at 30K miles?

I ran 20% winter/50% summer WVO with fryer oil cone filtration and no engine mods. I replaced the fuel filters every 5K miles more or less because that's a year of driving for me.

Consider also your engine oil change interval. I don't know what bio does when it dilutes engine oil but WVO washing down the cylinder walls doesn't do engine oil a lick of good. I kept it to 4K with dino and 6K with synthetic which was a gamble without oil analysis.

Sixto
87 300D

Hey,

I have a 2 tank WVO system from grease car and it works great. I change the WVO filter about every 6,000 miles (changed it 2 times). I get the oil changed every 3,000 miles. I will get the fuel filter changed at the next oil change interval.

As far as the engine temp goes, it idles between 80 and 100 with the AC on but going up hills it gets up to 100.

It hasnt done this before. most of the time the needle on the thermostat barely goes above 80. In the winter time it is just below 80.

Should I get the clutch/cooling fans looked at or just keep driving it and see what happens.

Thanks.

Keep driving.

Sixto
87 300D

Hey Sixto,

Thanks again for the advise


Chinu