1979 300 SD strange problem, car stops after 30 minute driving

[Mexx]

Just bought a 300SD 1979, perfekt shape, but with odd problems. The car starts, runs and accelerates perfectly, but after about 30 minutes driving (both highway and town) the gaspedal does not rev up the engine anymore.If I stop and floor the pedal in neutral it barely revs up and finaly the engine dies. After a few hours (maybe shorter, I always picked it up later) it starts and runs like nothing happend. This happend now for months and it is not getting better! I restored a 220 D from 1972(No electronicstuff)!! but the 300SD is a very complex car in comparision. Any Ideas anybody? A mechanic told me to remove the gas-cap and drive, because of some blocked fuelreturn line creating a vacuum in the gastank(?) but it did not help either.
2nd QU: My AC(newly refilled )blows only superHOT, no matter which temperature I dial in. Any clues someone?
3rd QU: I always read about vacuumpressure(hoses,..)What is this vacuum for? and how and where can I check if the pressure is right? Thank you everybody for ANY comment.My Car has been registered and insured since July and I drove only 100 miles.I am very frustrated, please help. Any affordable specialist in New York City?? Thanks for all Comments, Mexx.[:(]Your text here

[Karl Heinze]

Mexx,

It sounds like you have something in the tank that is clogging your fuel supply. Have you drained the tank and pulled the tank screen? Also, check your inline fuel filter by the IP. It may be partially clogged and closing off after a bit of a run. I have seen that happen before. Anytime I pick up a new diesel, I change all the fluids, filters, and perform a valve adjustment. Too often these items are neglected.

[tuttebenne]

Mexx - 12/13/2005 8:32 AM

Any affordable specialist in New York City?? Thanks for all Comments, Mexx.[:(]Your text here

I agree with the suggestion to change the fuel filters (2), this would be the first thing to do. I would also check to see if the rubber fuel hose is collapsing due to lack of strength. This hose is commonly called the "cigar hose" because it kind of looks like the shape of a cigar. Its found under the hood in line with the canister type fuel filter. Also track the fuel lines all the way back to the tank to see if someone had spliced a piece of rubber hose as a repair for a rusted fuel line. These could also collapse with age.

I know of a very competent and fair specialist in East Williston (Nassau County.) Don't know if this is too far for you.

Good luck.

[Mexx]

Thank you very much for your suggestions. Do I have to remove the gastank for cleaning? I never did this.
Any suggetions to help my AC to blow COLD? It is newly refilled but all I get is Super HOT! Any relays or electrical issues here? thank you all very much for all comments!