First drive in my 300CD in ~ 7 years...

[JHZR2]

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. 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? Keep in mind that this diesel relies upon a vacuum pump and vacuum manifold to give brake boost and engine shutdown... Thank you for any recommendations!

 

[Astro14]

Most likely a seized caliper. Might also be a collapsed brake hose. They fail internally and act as check valves, restricting the return flow of fluid and keeping the caliper in contact with the rotor. If you do the caliper, I would replace the hoses at the same time. ATE probably makes them and as I recall, W123 hoses were cheap...

 

[justintendo]

Originally Posted by Astro14

Most likely a seized caliper. Might also be a collapsed brake hose. They fail internally and act as check valves, restricting the return flow of fluid and keeping the caliper in contact with the rotor. If you do the caliper, I would replace the hoses at the same time. ATE probably makes them and as I recall, W123 hoses were cheap...

sound advice...too many times the hoses are over looked..

 

[ecotourist]

Why not fix the brakes and see if the "clunk" is gone?

 

[Lolvoguy]

Glad to see you got it running again! I still remember when you first got that car. As for the problem, also make sure the wheel bearings are spinning freely.

 

[bullwinkle]

A dragging caliper on one side would make it pull that way. Here's to hoping it's not the front sway bar, those are a nightmare!

 

[bullwinkle]

Also, the failure to shut down is a vacuum leak (or weak vacuum to the shutoff valve)-the shutoff valves (on the back of the IP) are known to leak, if there's oil in the line going to it, it may need a new one. If you have a Mighty Vac, that can test it too. Ignition switch or anything leaking vacuum, even excessive blowby or leaking power lock system can do it (my old ‘82 300D had issues with both, had to disconnect almost all vacuum to make the shutoff work).

 

[atikovi]

My vote is for a brake hose. Dealt a lot with those on cars that have sat a lot. Cheap first fix before replacing a caliper.

 

[Chris142]

Are you familiar with "Rollguy" on the Peach parts forum? He makes AC brackets to put a Sanden compressor on those cars. He also sells hose kits,condensers etc. I make many of his specialty AC hoses.

 

[KrisZ]

I agree with others that the dragging caliper may create a sensation of suspension movement. I would get that fixed and see how the car behaves afterwards.

 

[eljefino]

I had this issue on my w123 300d that had sat for ~2 years. End cause was likely a bad master cylinder that wasn't letting fluid back into it after releasing the pedal. I replaced pads/rotors/calipers and drove a few hundred miles with a rock hard pedal like I never noticed in any other car. Got further into it with rubber hoses, not them either, then finally replaced the m/c. I don't think there's a pushrod adjustment on it. My 240d suffered from sticky sliders on a rear caliper, but that was just rust that needed brushing/knocking off. Lots to check, but no more than any other car. The bleeders take a 9mm wrench, so it's good to know that's good for something. As you know, there's no lower front ball joint, and I've had the tire roll back and forth an inch when torquing lug nuts. An odd feeling. You could go around and see if one side does this way more than the other, could have a bushing issue.

 

[JHZR2]

Originally Posted by Astro14

Most likely a seized caliper. img] Might also be a collapsed brake hose. They fail internally and act as check valves, restricting the return flow of fluid and keeping the caliper in contact with the rotor. If you do the caliper, I would replace the hoses at the same time. ATE probably makes them and as I recall, W123 hoses were cheap...

It sure is a seized caliper. All that heat, not the same on each side, points to that. The car does have "new" (I.e. 7-ish year old) hoses. The old ones looked like this:

Originally Posted by eljefino

My 240d suffered from sticky sliders on a rear caliper, but that was just rust that needed brushing/knocking off. Lots to check, but no more than any other car.

I have to think that's it... Here's a pic I took when snooping around: (Bad side, note inner pad is more worn than outer fwiw) (other side) Did find this on the non seized side, may be part of the clunk reason. Don't recall it being an issue when I parked the car... I will be doing brakes, calipers included, all around,

 

[JHZR2]

Originally Posted by bullwinkle

A dragging caliper on one side would make it pull that way. Here's to hoping it's not the front sway bar, those are a nightmare!

It's not a pull, it's definitely more of a clunk that I can feel in the steering and/or floor a bit.

 

[JHZR2]

Originally Posted by bullwinkle

Also, the failure to shut down is a vacuum leak (or weak vacuum to the shutoff valve)-the shutoff valves (on the back of the IP) are known to leak, if there's oil in the line going to it, it may need a new one. If you have a Mighty Vac, that can test it too. Ignition switch or anything leaking vacuum, even excessive blowby or leaking power lock system can do it (my old ‘82 300D had issues with both, had to disconnect almost all vacuum to make the shutoff work).

Yes, I'm pretty familiar with the vacuum system on these cars. The curious thing was that the pedal was getting softer in the last mile or so of our trip (very consistent the whole rest of the time), and then and only then did we face vacuum difficulty. Never any other time in all of our errands stopping and going. Thus why I'm trying to correlate the shutoff issue to the brakes. The car is fine relative to the IP, unless thst valve just now went bad. I'd have my doubts regarding that luck... I did try pumping the brakes a bunch of times to see if it would firm the pedal. No luck. My fluid was exchanged when I did the hoses those years ago, and the car has sat out of the elements since. But there could be moisture at the end, or vaporized brake fluid, and that could be starting to compress... my suspicion is that was the case, I started pumping the brake pedal to see if I could form the pedal, and exhausted a bunch of vacuum in there. It takes some time to reestablish, and I shut it down shortly after that. Hoping that is all...

 

[Gasbuggy]

Very Cool. I swear I've seen that car before somewhere near the PA side of the Commodore Barry Bridge years ago, only time I saw those wheels in chrome. I just fixed a sticking caliper on my 76 300D. An old Benz tech I know says after 10 years of age the hoses on these cars can hold pressure on. The calipers come apart very easily. I took the pistons out and gave them a quick clean up with 1000/2000 grit. new hoses. Brakes are great now.

 

[JHZR2]

Originally Posted by Gasbuggy

Very Cool. I swear I've seen that car before somewhere near the PA side of the Commodore Barry Bridge years ago, only time I saw those wheels in chrome. I just fixed a sticking caliper on my 76 300D. An old Benz tech I know says after 10 years of age the hoses on these cars can hold pressure on. The calipers come apart very easily. I took the pistons out and gave them a quick clean up with 1000/2000 grit. new hoses. Brakes are great now.

I cross over the Commodore Barry if going to/from the Wilmington Amtrak station, so it's a possibility! I replaced the hoses not long after I got the car. So I have my doubts that it's the hoses. But I'm going to investigate more and see. What is strange to me is that the pedal is now much softer then it has been in any w123 I've owned. It feels more like my Chevy truck...

 

[Astro14]

You might consider rebuilding the calipers. As I recall, they are very expensive to buy as rebuilds, and Cardone, et. al, would worry me. If you go with rebuilds, find a specialty rebuilder that deals with MB.

 

[Gasbuggy]

Originally Posted by JHZR2

Originally Posted by Gasbuggy

Very Cool. I swear I've seen that car before somewhere near the PA side of the Commodore Barry Bridge years ago, only time I saw those wheels in chrome. I just fixed a sticking caliper on my 76 300D. An old Benz tech I know says after 10 years of age the hoses on these cars can hold pressure on. The calipers come apart very easily. I took the pistons out and gave them a quick clean up with 1000/2000 grit. new hoses. Brakes are great now.

I cross over the Commodore Barry if going to/from the Wilmington Amtrak station, so it's a possibility! I replaced the hoses not long after I got the car. So I have my doubts that it's the hoses. But I'm going to investigate more and see. What is strange to me is that the pedal is now much softer then it has been in any w123 I've owned. It feels more like my Chevy truck...

Yup, that had to be you. That's my area. You might have boiled the brake fluid in one caliper and now you've got a soft pedal leftover from it.

 

[JHZR2]

Originally Posted by Gasbuggy

Yup, that had to be you. That's my area. You might have boiled the brake fluid in one caliper and now you've got a soft pedal leftover from it.

Wouldn't brake fluid re-condense? Like... hours later? Or am I missing something? Probably was me, not many 300cd around here. Small world though!

 

[Gasbuggy]

Originally Posted by JHZR2

Originally Posted by Gasbuggy

Yup, that had to be you. That's my area. You might have boiled the brake fluid in one caliper and now you've got a soft pedal leftover from it.

Wouldn't brake fluid re-condense? Like... hours later? Or am I missing something? Probably was me, not many 300cd around here. Small world though!

Brake fluid absorbs water, the older it gets the more water it absorbs. Then if the fluid boils the water introduces air. Plenty of guys need to bleed their brakes after doing track days. Could also be that you glazed the pad/rotor and need more pedal pressure to stop?