1987 300D ...What is this part?

[iamtheosprey]

I changed my fuel pre-filter yesterday (clear plastic with a metal screen inside) and now I have a diesel leak.

First of all, within the old filter I found what looked like tiny bits of metal.

I didn't have a magnet handy except for magnetized screwdriver tips and it looked like they were iron.

Second of all, after installing the pre filter I started leaking quite a bit of fuel even when engine was off.

Today I got to fiddling around and found that whatever is connected to the pre-filter via fuel line was the culprit.

During installation I evidently caused the connection on this part to rotate upward. I pushed it back down and it appears as though the leak may have stopped for the time being and my performance is back.

While driving today I noticed that on hills especially that I was struggling where normally I could power up with no loss in speed.

All that stopped after I rotated the connection down.

Is it the lift pump or something like that?

Also, could it be in good shape still or is the fact that simply moving the intake causes a leak mean I should replace it?

[jay_bob]

If you are talking about the little barrel device below and rearward of the IP, with 4 connections, that is the fuel preheater thermostat.

Chances are when you rotated the connection that disturbed the seal.

This device is easily rebuildable using a rebuild kit available at the dealer or from this forum's sponsor.

In the mean time you can bypass it by direct feeding the lift pump from the pre-filter. I would not leave it bypassed especially in the winter. The other 2 hoses go to a heat exchanger wrapped around the heater hose at the upper rear left of the cylinder head (hidden under the intake manifold).

[iamtheosprey]

Originally Posted by jay_bob

If you are talking about the little barrel device below and rearward of the IP, with 4 connections, that is the fuel preheater thermostat.

Chances are when you rotated the connection that disturbed the seal.

This device is easily rebuildable using a rebuild kit available at the dealer or from this forum's sponsor.

In the mean time you can bypass it by direct feeding the lift pump from the pre-filter. I would not leave it bypassed especially in the winter. The other 2 hoses go to a heat exchanger wrapped around the heater hose at the upper rear left of the cylinder head (hidden under the intake manifold).

Thank you very much.

I wondered what those other two hoses were for.

Could this condition lead to water getting into the fuel?