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  #1  
Old 05-19-2019, 05:30 PM
JHZR2's Avatar
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Ran my 300CD for the first time in ~7 years...

Bought my 300CD in CA, drove it cross country, drove it quite a bit around on road trips, etc., then got caught up in figuring out window regulators, parked it in my garage, kids came and... Now Im trying to get it back going.

Had changed out the coolant to G-05...

Diagnosed a leaky schrader, so changed it...



Got tires mounted on my CalChrome Clear'ed 15" Bundts:



And went for a drive...

The AC charge is insufficient, and it was 86 out, so it was OK but not cool in the cabin. I can fix that.

There is a sound I hear at 40-50 but nowhere else, will need another thread on that...

There is no heat. Tried running the car with defrost on when filling, no dice. I dont particularly care about having heat besides wanting active chemistry in the heater core.

So the issue...

Driving along, under harder braking, like a more rapid stop at a red light, it felt like if I applied the brakes it was OK, but let off there was a front end clunk. Like something is loose in the front end.

Now remember that when I parked it, Id drive the car anywhere. Literally did. Ran great, nice AC, etc. I did stuff to it, but never encountered this. Almost feels like the suspension is shifting forward and backwards a tiny bit when doing this braking action...

So I got home and checked the wheels - left front wasnt able to be touched. Immediately jacked the car up, could barely touch the lugs, got them off with my impact. Got out the IR camera.





(ouch!)



This is it in real life. Nothing could be touched 15 minutes after removing the wheel.



For reference on the other side...



Which still seems a bit hot to me...



I know, not the exact same spot on the rotor, but it was much cooler overall.

So... I guess it means seized caliper, and need to re-do the entire brake system. Not a big deal.

But my questions are now:

1) When braking, it felt like something in the front suspension was shifting back and forth very, very slightly. Maybe it was a seizing of the pads to the rotor? nothing on the front is loose, I had rebuilt most of the front suspension, and the steering on this car is tighter and better than any W123 or 126 Ive ever driven, including my 240D with 73k miles. Is there something else I should check given that the typical play and shake tests yield nothing, and it only happens after a hard stop?

2) We drove all over doing errands. Probably 30 miles, six startup and shutdowns, etc. All was perfect. But the last leg, the last 2 miles just in town, slow to get home, the braking got softer in the pedal, and after I pulled up in my driveway and tried to shut the car off, it hesitated to shut down. Im not sure that the continuously softer pedal and the difficulty shutting down were coincidental. But Im not sure the seized/hot caliper is the same error as if there is a brake booster/vac issue. Any thoughts?

Thank you for any recommendations!

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)
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  #2  
Old 05-19-2019, 06:39 PM
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When I encountered something similar, re-torque of the caliper bolts seemed to resolve the "shift".
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84 300SD 350K+ miles ( Blue Belle )
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  #3  
Old 05-19-2019, 07:42 PM
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Quote:
Originally Posted by JHZR2 View Post

2) We drove all over doing errands. Probably 30 miles, six startup and shutdowns, etc. All was perfect. But the last leg, the last 2 miles just in town, slow to get home, the braking got softer in the pedal, and after I pulled up in my driveway and tried to shut the car off, it hesitated to shut down. Im not sure that the continuously softer pedal and the difficulty shutting down were coincidental. But Im not sure the seized/hot caliper is the same error as if there is a brake booster/vac issue. Any thoughts?

Thank you for any recommendations!
Pull off the main vacuum line connection that screws onto the vacuum pump. Fish around in there and see if any debris or the vacuum check valve broke off. That can clog up and reduce vacuum.
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  #4  
Old 05-19-2019, 09:25 PM
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Man that's HOT, you think the bearings and grease are ok?
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1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

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  #5  
Old 05-19-2019, 09:31 PM
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That brake rotor is such a pretty shade of blue.....

Time to look for restriction in fluid back flow, might well be a hose .

Don't forget to re pack the wheel bearings .

Nice looking Coupe ! .
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1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

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  #6  
Old 05-20-2019, 12:20 AM
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Quote:
Originally Posted by SD Blue View Post
When I encountered something similar, re-torque of the caliper bolts seemed to resolve the "shift".
Aren’t those single use bolts? I will give that a try for diagnosis purposes.


Quote:
Originally Posted by HarvAMG View Post
Pull off the main vacuum line connection that screws onto the vacuum pump. Fish around in there and see if any debris or the vacuum check valve broke off. That can clog up and reduce vacuum.
I had to move cars in the driveway so I pulled it out and then back in. The booster/pedal is still very soft, feels more like my Chevy pickup then any w123 I’ve owned. Not clear what that means... but the engine did shut off as normal when I did that vehicle exchange. So I suspect that it may have been my pumping the pedal that affected shutdown due to the firm, pumping motion Imapplied to see if I could get my pedal harder again.

So it begs the question, what made my brake pedal go soft and stay that way?
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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)
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  #7  
Old 05-20-2019, 04:12 AM
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My vote is for a stuck brake piston - though it is always best to check fixings / mountings / rubber parts if a car has been sitting for a while.
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1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #8  
Old 05-20-2019, 07:23 AM
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Clunk braking is usually guide rod bushing/ mount
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My drivers:
1987 190D 2.5Turbo
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1987 300TD
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  #9  
Old 05-20-2019, 07:55 AM
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Quote:
Originally Posted by vstech View Post
Clunk braking is usually guide rod bushing/ mount
I know. That’s my consideration/concern.

Not really sure how it could go bad while sitting, but that will be something to pursue. I’d suspect that if one brake is dragging like it is, perhaps the tire front end has a bit of misalignment or pull on it due to that, which might then make a part that is marginal behave worse. Not looking forward to that job if it is required...

I’m going to re do all the brakes and go from there when I have time...
__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)
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  #10  
Old 05-20-2019, 09:08 AM
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I agree that the heat problem is probably a sticking caliper. Had the same problem on my '81 300SD; changed it out and problem resolved. Before that I could take a short drive and the wheel would heat up so much I could not touch it. Other three wheels would be fine.
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  #11  
Old 05-20-2019, 06:35 PM
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Some of your difficulties are probably directly related to that stuck caliper.
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  #12  
Old 05-21-2019, 01:20 AM
JHZR2's Avatar
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Yes, the caliper is my first job to fix, potentially before I even do a real brake job.

I’m not quite seeing how I can get the clunking feeling upon brake pedal release without something else in the front suspension being off, but not sure what it could be either.
__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)
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  #13  
Old 05-21-2019, 11:20 AM
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Exclamation Work Smart

And do the entire job in one go, it'll be faster, easier and cheaper plus a better job in the end .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better
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