Hello all. In my search for the culprit as to my less than stellar fuel mileage in my '79 300D (about 18-20mpg) many of you provided me with lots of great advice.

Bad MPG Blues

Well today, after changing the oil, I was running the car with the air filter cover off and I heard a sound I've heard before but in an exhaust valve in a former vehicle of mine. It's half a pop and half a ffffttt sound from one cylinder: I have an intake valve that's leaking clear as day. You can even feel it if you put your hand over the intake opening. It also happens to coincide with this new meter lope it developed which is really just one cylinder cutting out at idle.

As a result, with at least 280K miles on this motor, assuming the junkyard it came out of was correct on its original mileage, I'd say I'm looking at a rebuild. I figure why not just do the rings, oil pump, head work, etc... and be done with it.

So aside from the obvious stuff,
timing chain
rings
gaskets
head work
new oil pump

What else should I replace/look at while I'm in there? Also, on the outside chance anyone knows of any method to get an intake valve to start working again even temporarily, I'm all ears.

Frank.

__________________
'82 300SD

Just checking - you've checked the valve adjustments lately?

If you haven't done this maintenance item, I'd try it for results first. I get the impression from reading posts here that the valves will eventually not close properly if you don't keep up with this task every so often. Mercedes says every 15,000 miles - some say you can go longer - but you have to do it.

Ken300D

2 grand for a rebuild! Yikes. That's some dough. It's 2 grand for a junkyard motor that I know nothing about so I'd still lean towards the rebuild for the piece of mind. Heck I still have the original motor in which the rings went bad in my garage. I really don't need two old motors sitting around if you know what I mean.

As for the valve adjust, I should have included that I did that about a month ago. It ran a little better but not much. I believe, based on another post I read a while back, I probably have oil deposites built up on the intake valves from oil leaking down the valve guides interfering with the valve's ability to seal.

So for what it's worth, what else might I replace when I rebuild it besides what I already mentioned?

Thanks

Frank.

__________________
'82 300SD

Scapegoat, just curious, where do yo come up with the 2 grand rebuild price? I went on fast lane did some pricing, here's what I found.

Oil Pump 173.10
Rings 143.29
Valve seal kit 9.67
Timing chain 84.93
Crank case gasket set 61.23
Head gasket set 55.89
Head Bolts ( hear you stretch 'em when you torque 'em down)
It seems there are 25 and they break down as follows
12X145mm (8) @ 5$ ea. 40.00
12X120mm (9) @ 2.24 ea. 20.16
12X105mm (5) @ 2.23 ea. 10.15
8X20mm (2) @ 200 ea. 4.00

all this for a grand total of 602.42. At that rate I could send the head in (as opposed to doing it myself) to get lapped, valves seals, etc... and still get out under a grand. Unless of course I'm missing something big.....

Frank

__________________
'82 300SD

Here are a few more to add to the list.

Rod Bearings
Main Bearings
Crank Bearings
Valve Job
Did you add chain for oil pump?
Head Gasket
Intake Gasket
Exhaust Gasket
Cam gear {if worn}
Crank gear {if worn}
I would have the freeze plugs replaced
And depending on the shape of the cylinders you may need new sleeves installed at Machine shop
I would do all the hoses and belts.
Good luck.
Charlie

The gaskets are in the gasket sets I mentioned.

I'm going to hold off on the crank bearings, last time my dad and I pulled the engine on our old 67 200D with over 400K miles on it(chip broke off the prechamber so the head needed work.), there was no wear that we could detect on the lower end bearings. Put the motor back together with 'em on and went years with out a prob. Eventually sold it, never did get new lower bearings and never needed 'em.

Definitely going to do a valve job. I'm going to start shopping some machine shops tomorrow morning. Last time I had that done it was about 300$, don't know what this will be.

Didn't think of the oil pump chain, I'll look into that for sure. I actually might just old off on the oil pump as I can change that later with the motor in the car. Since the gauge samples pressure right off the motor, I'll know if it goes. (As long as I check gauges once and while.) Also, if the sound of the engine when she's pressuring up after an oil change is any indacation of low oil engine sounds, I don't think I'll have too much trouble noticing a pressure drop.

I should also add, I need 3 to 4 years out of this car while I'm in school. After that, I'm getting a newer one.

Thanks for the help, good advice from all.

Frank.

__________________
'82 300SD

Elripster, where did you price the parts? I, Coincidentally, am looking at the possibility of rebuilding my motor.....or maybe just buying one of those fancy new LADAs

The prices here are from Fastlane. I hae a Performance Products catalog too, but the prices seem comparable. One thing I've noticed about Perf. Prod. is they seem to be out of stuff often when I order form them.

Frank.

__________________
'82 300SD