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  #1  
Old 04-29-2005, 01:15 AM
Veloce300DT's Avatar
TEAM MULHOLLAND
 
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Timing Chain??

how long do the timing chains typically last on a 617.952?
I have a feeling mine may need to be tightened or replaced.

I have an 84 300D and I have been experiencing a rough idle (motor mounts are new, and valves were recently adjusted within the past 10K miles) and I am also noticing a power delivery problem at low rpm speeds... take off from a stop seems to be healthy- quick, BUT there defintely doesnt seem to be as much power as usual. I really notice the power loss when decelerating and then accelerating.... as one does when exiting a freeway for example- reducing speed (exit ramp light turns green, dismissing the need to stop or continue to decellerate) and then accelerating. Theres very little power and I find myself with the pedal to the floor in situations like these..... just to keep up with traffic.

There is no smoke when the engine is warm.... very little soot. But at start up on a cold engine there seems to be some light puffing of smoke.

Another possibloe symptom of excessive stretch of timing chain in addition to loss of power and rough idle is some mild overheating after shut off.... say i drive at 75mph for 25 minutes, exit the freeway, stop and go street traffic for 2 miles, then park, let idle down, and shut off. Whenever i start the car up within a few minutes after a drive like this the temp gauge rises up to nearly 100 deg. and the lowers as i start driving.

Am I correct to assume my timing chain could be over-stretched?
I just turned over 188K miles.

As always- comments/info.greatly appreciated!!
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1995 E420
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  #2  
Old 04-29-2005, 01:44 AM
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those lousy chains are only good for 300K-500K miles. Search for valve adjustments and timing. Lots of good info.
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  #3  
Old 04-29-2005, 02:20 AM
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At 160k miles the chain on my 240D is stretched about 3 1/2 degrees. Adjusted the injector pump timing to compensate for this and performance picked up tremendously.
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Old 04-29-2005, 02:47 AM
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At 188K miles you should not need a new timing chain, but you can easily check the stretch when you have the valve cover off for valve adjustment. Power loss at highway speeds is typically a clogged fuel filter. It is normal for coolant temp to increase somewhat after shutdown after a high-load run, especially with these iron heads that store lots of heat and transfer it to the stagnant coolant. When you start your engine, the coolant starts circulating, thus cooling the engine. A new thermostat may help keep coolant temps lower.
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  #5  
Old 04-29-2005, 03:27 AM
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Thanks for the replies guys!

I checked my records and my last valve adjustment was at 177K miles, so to be precise, its been 11K miles since my last valve adjustment. Seems a tad early to have valves that are excessively out of adjustment to cause the amount of rocking that the car exhibits when running at warmed up temp. at idle. But who knows....

I figure now is a good time to go through the whole car and sort out everything, just before summer hits. So next week in addiitiion to an oil change, the valves, idle, fuel system, injectors, injection pump, coolant and climate conntrol systems will be checked and adjusted as necessary. Glad to know the timing chain should have some life left in it...
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1995 E420
1992 BMW 525i
1984 300D Turbo sold
1993 Volvo 244 sold
1995 Volvo 944T R.I.P!


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  #6  
Old 04-29-2005, 09:14 AM
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Quote:
Originally Posted by Veloce300DT
I checked my records and my last valve adjustment was at 177K miles, so to be precise, its been 11K miles since my last valve adjustment. Seems a tad early to have valves that are excessively out of adjustment to cause the amount of rocking that the car exhibits when running at warmed up temp. at idle. But who knows....
search on "rack damper"
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  #7  
Old 04-29-2005, 10:47 AM
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So how exactly does one check the slack in the timing chain when adjusting the valve? is it as easy as rocking it back and forth? I recently had my valve cover off to replace the gasket and was going to do the valves but I didn't have a feeler gauge that went to a small enough size. I'd like to check the chain when I do the valves again soon. I've got good service records on my car but none that mention when the valves were last done.
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  #8  
Old 04-29-2005, 12:24 PM
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Sailor and Volce,

The elongation (its not stretch, its wear) of the timing chain is measured on the engine vibration damper by how many degrees late the timing is when the cam is at the notch on the cam towerr.

If the cam timing is within 4 degrees its usually OK. Offset woodruf keys are available to correct the cam timing to compensate for wear of the chain and the IP can be adjusted accordingly.

P E H
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  #9  
Old 04-29-2005, 12:51 PM
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The notch on the cam tower is a good rough indicator that can tell you if you need to adjust that timing. If you decide to adjust it, you use the more accurate measurement based on crank position when the #1 intake is at 2mm lift to determine what offset key you use and/or replace the timing chain.
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  #10  
Old 04-29-2005, 02:50 PM
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Check the chain stretch via the cam timing gear mark and crank indicator very carefully. I agree with Pindelski that this is easyest if you remove the fan and shroud. Then you can crank with ease from above and really get the cam gear in perfect alignment with the marker.

If you have 2 degrees or less chain stretch, you're not going to be impressed with re-timing the IP and putting in an offset woodruff key to get the valve timing back to where it should be. A couple degrees off just isn't a big deal in performance, and even 3 degrees will be more of a fuel economy issue.

Your off the line acceleration problem is more likely to be solved with an ALDA adjustment. I'm sure you can find a write up in the archives. The ALDA adjustment on the IP is very easy and can provide a profound improvement in performance. No other adjustment is so immediately satisfying!

Your rough idle is most likely caused by injectors. Try some diesel purge. I finally built my own pop tester so I could match my injectors. Now I've got a great idle.

Bruce McCreary
(2) '85 300Ds, '83 300CD

Last edited by BruceMcC; 04-29-2005 at 02:56 PM.
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  #11  
Old 04-29-2005, 04:17 PM
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Quote:
I finally built my own pop tester so I could match my injectors. Now I've got a great idle.
How did you do that? I would like to do that myself.

danny
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  #12  
Old 04-29-2005, 04:50 PM
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As far as my power problems go, off the line acceleration seems to be very healthy in terms of how fast the car speeds up, however, the amount of throttle I have to put in seems to be excessive. I have to floor it. II tiimed my acceleration from dead stop to 60MPH on a flat road. I clocked a healthy 14 seconds. However, I had to floor it all the way up to 60MPH, and while normally you have to floor these cars, I dont feel like im getting thhe same amount of power that I normally get when my car is running right- seems like the engine is having to work harder than normal.... i guess the perfect way to describe it is to say that it feels like I am driving at a high elevation, although I live 5ft below sea level.

Now, with that said, I have been running BG 248 (diesel fuel addiitive- boosts cetane, disperses any water that mayy be in the fuel, and cleans injectors) EVERY tank for the past 10K miles. I have very little visible soot.
This power loss problem really shows itself when I am decelerating... as I mentioned above- if I am running at any speed and let off of the throttle, and then step backk into it... there is a tremendous lack in power.... the rpms max out at every shift, and the engine feels very meager.... and I HAVE to floor it... which isnt normal considering how the car used to drive. Accelerating from any given speed with smoothness and ample power used to be one of my favorite thhings about this car.... it was never FAST but I NEVER had to floor it unless I was going up a hill.

I want my engine back! I feel like someone has stolen my good ol 617!
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Nate

1995 E420
1992 BMW 525i
1984 300D Turbo sold
1993 Volvo 244 sold
1995 Volvo 944T R.I.P!


"The details are not details. They make the product."
-Charles Eames

www.cbs.nu
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  #13  
Old 04-29-2005, 06:13 PM
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Maybe you're not getting any turbo boost. Check the plastic vacuum line running to the ALDA on top of the IP.
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  #14  
Old 04-29-2005, 06:26 PM
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Yeah if it just happened suddenly you should check to see that it's boosting. May have a plugged banjo bolt, broken banjo line, something disconnected.
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  #15  
Old 04-30-2005, 04:17 PM
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I don't see how he could have bad boost pressure to the IP if he still gets 14 seconds to 60mph. Reduced boost signal should hurt his acceleration greatly.

So it is more of a throttle responce issue??? Perhaps the throttle linkage needs looking at.

As I recall, disconnecting the overpressure sensor at the intake manifold DISABLES the boost. You have to bypass the overpressure relief valve at the firewall.

Bruce McCreary
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