Hello all,
I was changing the oil in my 86300sdl yesterday and noticed that the rubber hose that attaches to the wastegate was dry rotted and cracked. I replaced it with a piece of fuel hose that I had. What does this hose do? If it was cracked and leaking what would my symptoms have been? The car seems to drive the same as it did before I replaced this hose. I get 25-27mpg all the time. I have 90,000 miles on it. It uses no oil. I use Mobil One 5W-40 Truck and SUV synthetic oil. EGR has been disconnected. Turbo spins up normally.

If this is an important piece of rubber hose, why is my car still running the same?

Thanks
John

The hose provides manifold pressure to open the wastegate and prevent excessive boost from the turbo. The spec is about 12 psi as a limit.

Without the hose, the turbo can probably get over 20 psi. There is a safety "overboost protection valve" on the firewall that should dump fuel enrichment at a manifold pressure of 15 psi and effectively drop the boost.

A cracked hose will usually function in similar manner to a integral hose, provided the hose is relatively intact. The SD had a similar situation recently and it never reached unsafe boost levels AFAIK.

Thanks for the reply. The hose was intact, just had stress cracks in it. The hose I used to replace it was a German braided fuel hose from my 67 VW Beetle. It is a little smaller in diameter that the original rubber hose. Do you think that might make a difference, or should I find a larger diameter hose?
John

It will be fine. There is very little flow through the hose.

I would replace it with something a bit more heat resistant. It gets a bit warm in that area. I have heard of people using silicone to replace the hose as it offers better heat resistance than the factory material.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine