1985 300D back from near death - Page 4 - PeachParts Mercedes-Benz Forum

Diseasel300 · #46 09-21-2017, 11:25 AM

The injection pump has a maximum RPM limit built in, it will not pass that, despite what the tach says. Think of it as a rev limiter. Even if you do hang in gear too long, it'll still be governed by the IP, so there's not a possibility that the engine is going to grenade from some ridiculous speed.

300Drestoration · #47 09-21-2017, 11:28 AM

So then is there a possibility that i will never reach third gear in WOT?
Should i basically expect a super duper long high rev PLATEAU and then somehow it'll shift to 3rd at some point after that's held?
Or should i rather expect 3rd to be reached during an increase in RPM's?

Diseasel300 · #48 09-21-2017, 11:31 AM

It's difficult to say what will happen, that's why you're doing a test.

One of 3 things will happen:

1: You will get 3 high RPM gear changes (~4500 RPM or so)
2: You will get a hung gear change (stuck at 4500-5000 RPM) and immediately dump into 3rd then 4th
3: You will simply get stuck at RPM limit in 1st with no upshift to any other gear

300Drestoration · #49 09-21-2017, 11:43 AM

ROGER THAT!
will post back when i get to crank the pedal somewhere..

vwnate1 · #50 09-21-2017, 12:53 PM

You need to stop skipping steps .

Go back to #1 and have the damned valves adjusted .

You're endlessly asking "but what if ?" questions instead of following the good advice you get here .

300Drestoration · #51 09-21-2017, 01:06 PM

Quote:

Originally Posted by vwnate1

You need to stop skipping steps .

Go back to #1 and have the damned valves adjusted .

You're endlessly asking "but what if ?" questions instead of following the good advice you get here .

This is the first time i'm hearing that this needs to happen first. How's a new guy to know this? I even mentioned that topic just a few posts ago, trying to be clear here and do it right.

Every time i ask anyone what to try given my symptoms i get a different opinion. And then i pursue it, thinking that i am then following to good advice i get here.

This is the first vehicle i've ever owned in my life. 37, lived in cities till now. I'm doing a pretty good job so far. Installed a damn turbo alone without breaking anything (rusted bolts, bones, etc).

i guess i'll get them valves adjusted.

Also, budget planning is a factor. I'm not going to blindly toss steps of investment without having a whole sense of what is at issue still. I.E. it would be helpful to know my transmission needs B1 repaired (major expense) before tossing money at valve adjustment, timing chain and adjustment, exhaust line, and panels. Some folks have encouraged me to consider the car too much of a money pit and just fly to arizona and pick up a rust free vehicle for 4 or 5 K and drive it home.

The car has been relatively low total cost so far (maybe 2500 or 2800) but it's at a point where if i throw another sets of a few hundred into it and discover the entire thing will require quite a bunch more after that, well..it's just nice to know things sometimes.

So, valve adjustment now?

vwnate1 · #52 09-21-2017, 02:01 PM

O.K. ;

I obviously thought you were the guy who in other, previous threads said he'd had the valves adjusted . sorry 'bout that .

Yes, along with that very first HOT oil & filter change the valves should have been adjusted before you ever touched the turbocharger .

It's a simple job for the Mercedes Mechanic because he'll have the correct angled wrenches, best done with the engine stone cold and shouldn't cost over $125 as it's a 1/2 hour job .

It will greatly improve cold weather starting as well as smooth up the idle even more and yes, it even affects shifting (not the missing 2nd gear though) because the TV cable is affected by how much throttle you need to apply and tight valves require more foot action to do the same job .

Don't be fooled by '! rust free Az./Ca. cars!' hype ~ I live here and most of the ones for sale haven't been maintained and need $2K + of work to be daily drivers .

The timing chain is either good or not, there's NO ADJUSTING IT . the Mechanic will (should if he's any good) automatically check it as no cost when he's adjusting the valves .

Sooner or later you're going to get this one sorted out .

Diseasel300 · #53 09-21-2017, 02:11 PM

Well that escalated quickly... Holy cow!

The valve adjustment is important for refinement and ultimate power and economy, but it won't cause a missing gear!

Let's put the horse back in front of the cart... You're trying to troubleshoot a transmission problem. The car runs, maybe not factory-perfect, but enough that you're not complaining about it. Let's troubleshoot the transmission first, then worry about refinement issues. Sloppy valves aren't going to make a damn bit of difference on your WOT tests anyway.

Work on one thing at a time. If you get carried away doing every suggestion that every person makes on a variety of different things, none of them will ever get done and you'll wind up extremely frustrated. Speaking from experience, if you try juggling too many projects at once, you'll become disenchanted with the car and develop a loathing of its very existence (thoughts of dousing it in gasoline and striking a match WILL come creeping into your thoughts!). It's a soul-crushing experience to be tackling multiple problems and NONE of them are making any progress to show for it!

300Drestoration · #54 09-21-2017, 03:12 PM

That is how i had interpreted the valve adjustment as well, being a power/efficiency refinement but not something that will suddenly fix an actual system issue.
However, i suppose the other perspective regarding addressing the valve adjustment first is so that one can at least eliminate it from something that could be causing poor behavior which might otherwise distract from solving bigger issues.. but what observable poor behavior would that be? Would a non adjusted valve state effect RPM's and throw off my assessment of shifts in this test?

Diseasel300 · #55 09-21-2017, 03:32 PM

If you have loose valves, you will have a noisy valve train and will be causing excessive wear to the camshaft compared to properly adjusted valves. Too tight of valves will cause the valves not to seat properly and will cause low compression or leakdown of combustion, usually resulting in poor power, rough idle, or grey smoke.

None of that will affect a transmission test. You are solely forcing the transmission to do what it was designed to do - shift gears. You're looking for how many gears it shifts through, you don't really care how well it does it or at what RPM it does it at. You only care that it shifts right now.

Go do the test already and get back to us. If it turns out you really do have a B1 problem, then you can go down that avenue. If it turns out you actually have 4 gears but it isn't shifting properly, then we can help you tune that instead.

300Drestoration · #56 09-21-2017, 04:43 PM

Was able to do a brief test but am off now to find a place to do a more thorough test.
Happened upon a highway onramp that was level by luck, and with nobody behind me I was able to start from near stop. Gunned it and reached 5200 rpm and had to back off due to running out of entrance road and plenty of traffic to enter ahead.
Never a hint of shifting. Nice white cloud though. Not grey or blue.
As soon as I let off the gas I of course was at a nice 3rd gear when I started accelerating again.
Will see what I can do next...

300Drestoration · #57 09-21-2017, 05:13 PM

Ok i was able to pull off 3 good tests and the results were identical..
RPMs plateau completely at 5000 and stay there and it's just a brick wall. I held it for a while each time, maybe up to 10 seconds entirely at 5000. No shift at all.
Interestingly, there was virtually no smoke for these 3 tests. Just for that one getting on highway. Maybe I cleared out the sinuses.

Diseasel300 · #58 09-21-2017, 05:58 PM

Now you've conclusively proven that you have a valve body problem or a piston problem of some sort.

With transmission problems, you start to teeter on the edge of get rid of the car or fix it. If you pay someone to work on the transmission, you're talking some pretty big bucks. Doing it yourself still isn't going to be cheap, but it will be a fraction of what a shop will charge you.

300Drestoration · #59 09-21-2017, 06:03 PM

This is why I have held off on certain modest chunks of investments.

So, yes, back to the parts car... if it's transmission seems to be performing well enough, and i can get it for 500$ ish, do I go for it and pull the tranny and the exhaust line and maybe other parts and maybe even panels.

Back to square one.

Diseasel300 · #60 09-21-2017, 07:22 PM

I guess it sorta depends on the condition of the parts car? Is it in better overall shape than yours is? It may be a better idea to use your own car as a donor and fix up the parts car? Not sure what your skill level is or what your long term plans are, but I gather your idea is to take 2 cars with faults and make 1 good one out of them.