Ben the 1980 300SD Lives!!!

Gentleman Ben, the beloved 300SD, has now recovered from the unpleasant 3-piece camshaft episode (change out your vacuum pump before this happens to you!). After almost 2 years in the home hospital, a good used engine,
rebuilt transmission from Adsitco, a double buff & wax, and a lot of TLC it now ticks over like a sewing machine and is ready for daily driving.
Questions to the group to aid final recovery:
The heat now doesn't want to shut off. Without doing a lot of troubleshooting I am thinking that something in the heater servo valve or the control unit may have gotten stuck or corroded during the extended idle spell. I've already corrected some electrical glitches caused by corroded contacts in the lighting. Are there any typical failure modes in the climate control system? I am about to go through the CD to gain familiarity.
Does anyone out there rebuild the servo valve and control unit for reasonable prices? The options I see at Rusty's and Performance Products and Adsitco seem pretty high for these parts ($250-$1400).
Thanks again to Mr. Lambert and other frequent contributers for the advice I've gleaned over the years.
Next in the emergency room is the 1986 300SDL with the possible cracked head.
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the cutlets, top with parsley, lemon slices and cracked pepper. Serve with spinach salad, macaroni and cheese (homemade) and iced tea...
Spaghetti with Real Italian Meatballs
If you don?t have an expendable bambino on hand, you can use a pound of ground pork instead. The secret to great meatballs, is to use very lean meat.
1 lb. ground flesh; human or pork 3 lb. ground beef 1 cup finely chopped onions 7 - 12 cloves garlic 1 cup seasoned bread crumbs ½ cup milk, 2 eggs Oregano basil salt pepper Italian seasoning, etc. Tomato gravy (see index) Fresh or at least freshly cooked spaghetti or other pasta
Mix the ground meats together in a large bowl, then mix each of the other ingredients. Make balls about the size of a baby?s fist (there should be one lying around for reference). Bake at 400°for about 25 minutes - or you could fry them in olive oil. Place the meatballs in the tomato gravy, and simmer for several hours. Serve on spaghetti. Accompany with green salad, garlic bread and red wine.
Newborn Parmesan
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for a smooth consistency, then mix again. Form the sausage mixture into patties or stuff into natural casings.
Stillborn Stew
By definition, this meat cannot be had altogether fresh, but have the lifeless unfortunate available immediately after delivery, or use high quality beef or pork roasts (it is cheaper and better to cut up a whole roast than to buy stew meat).
1 stillbirth, de-boned and cubed Ό cup vegetable oil 2 large onions bell pepper celery garlic ½ cup red wine 3 Irish potatoes 2 large carrots
This is a simple classic stew that makes natural gravy, thus it does not have to be thickened. Brown the meat quickly in very hot oil, remove and set aside. Brown the onions, celery, pepper and garlic. De-glaze with wine, return meat to the pan and season well. Stew on low fire adding small amounts of water and seasoning as necessary. After at least half an hour, add the carrots and potatoes, and simmer till root vegetables break with a fork. Cook a fresh pot of long grained white rice.
Pre-mie Pot Pie
When working with prematurely delivered newborns (or chicken) use sherry; red wine with beef (buy steak or roast, do not pre-boil).
Pie crust (see index) Whole fresh pre-mie; eviscerated, head, hands and feet removed Onions, bell pepper, celery ½ cup wine Root vegetables of choice (turnips, carrots, potatoes, etc) cubed
Make a crust from scratch - or go shamefully to the frozen food section of your favorite grocery and select 2 high quality pie crusts (you will need one for the top also). Boil the prepared delicacy until the meat starts to come off the bones. Remove, de-bone and cube; continue to reduce the broth. Brown the onions, peppers and celery. Add the meat then season, continue browning. De-glaze with
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AFAIK the climate control system is designed so that when the control unit fails, it won't do anything other than give heat, so I think that's your culprit on that front. If you want better prices on parts and don't mind going used, check pgauto.com. They have a storefront not too far from me and as my car ages it has quite a few parts from them in it, the oldest being an 8 year old heater blower, which means the used unit has lasted almost as long as the original and shows no signs of impending failure. Richard

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What happened to your vacuum pump? How did it fail? Was it a diaphram pump?
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The most common failure mechanism is for the climate control servo to go bad. This controls the heater core water flow, vacuum flaps for the heat/ac system, compressor, fans speeds, etc. One failure mechanism is for the lower plastic case to crack and leak water into the motor/grear train and destroy it. If you see coolant dripping from it, it's shot. It also has a feedback potentiometer in it that's part of the resistor chain that maintainst the set temp. Like all pots, it is subject to dirt/bad spot's developing, particularly if it hasn't been worked in awhile. That's why it's advisable to cycle the system from max heat to max cool about once a month.
Another common failure is the amp module that drives the servo. The servo is located in the engine compartment, pass side, near the firewall. The amp is directly behind the glove compartment. These are easily replaced and go for about $100
If you get to the point where you want to try to directly drive the servo, you can do that with a 9V household battery. You need to locate the two connectors on the servo that run the motor inside the servo. They can be found on the service diagram. Disconnect the two wiring harnesses from the servo Applying the battery in one direction will wind the motor all the way to full cool, reverse the polarity for full heat. And only apply it for a short period, if it's working, you will hear the motor whir. When it stops, its at the end of its travel, (full heat or cool) so dont leave the battery connected or it will burn out the motor. If it's an issue with the pot, cycling it back and forth a few times may restore it.
You can also measure the resistance of the pot through the terminals to verify it that's the problem. If it is, it's possible to remove the top of the servo and spray cleaner into the pot. Beyond that, the rest of the servo is beyond the servicing of mere mortals.
If you need a new one, George Murphy at Performance Analysis, in TN sells rebuilt ones. He replaces the lower plastic housing with an aluminum one. I think he charges $5-600 for one. However, beyond the one yr warranty, he offers lifetime repair for $100, which I think makes it a good deal. I've had one for about 2 yrs now and it's been working fine. Also, T.G. said he was putting one of the new digital ones, that replaces the whole craptacular system of servo and amp, so you might want to check with him if it turns out you need one. I think those were a few hundred $$$ more.
Good luck!
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snipped-for-privacy@aol.com (VCopelan) wrote in

Thanks to all for your advice. The unit has fortunately broken loose and is working OK now (the AC still needs to be recharged / converted).
The vacuum pump that failed was a piston type. It might have been the original with 250M miles. The spring and lever are missing (probably in the sump or out the exhaust pipe) and the pivot bracket was broken. I had just had the timing chain changed a month before, but the parts got tangled in the chain and it jumped time. My son, who was driving it, said it had chugged for about 20 seconds as he tried to turn around and head for home. Then there was a frighteningly loud crack followed by silence as he coasted to a stop. The autopsy found that the timing chain was broken, the camshaft was in three equal length pieces, and the front three aluminum cam bearing towers were broken. No 2 cylinder top shows just a light scratch corresponding to the valve that it met. I think that the cam towers are probably engineered to fail first to save the bottom end. I will further tear the block down to be ready for a complete overhaul if the replacement 'used' engine shows signs of eventual weakness.
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I have a 1980 300CD which snapped a timing chain at 208,000 miles. My diaphram type vacuum pump did not contribute to the failure but I never did determine the actual cause of the failure. I broke my timing chain in two places. Several camshaft towers also snapped. The timing chain cut a hole in the upper oil pan. However, the force of the chain stopping also broke off the crankshaft wood drift key and welded the crankshaft gear to the crank. My machinist welded the wood drift keyway back into shape. About $2,500 later I rebuilt my engine with new Mahle pistons, a new head, oil pump, oil pump intermediate gears, chain tensioner and exhaust valves. I'm still using my original vacuum pump at 273,000 miles because I couldn't find anything wrong with it upon diassembly. Do the vacuum pumps often fail? Should I change mine?
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snipped-for-privacy@aol.com (VCopelan) wrote in Writes:

I had read here and been told by a Mercedes mechanic (after my incident) that the vacuum pumps last up to 200M miles and should be preventatively changed out. My offending piston type was frozen in the sleeve when I disassembled it. I went with back with a new one from Rusty on the replacement 'used' engine. Due to a parts ordering mixup I have rebuild kits for both a piston and diaphragm type that could be let go for a fraction of the original cost.
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I'll have to speak to my mechanic about vacuum pump replacement. I have friends who have driven their 240D's to over 400,000 on the original vacuum pump with only diaphram replacement. The diaphram pump is so simple, it's hard to believe that much could fail. I guess the bearing on the cam follower could go?
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It is like you said... stuck servo. Take the hoses off and see if you can somehow free the valve... Once freed, I think it will be fine... try this before you decided to replace the entire servo.
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Congratulations on your restoration job, many others would have give up.
The climate control system has two troublesome components: the "amplifier: (logic board} which is located behind the glove box - remove the glove box to access it - look for a cigarette size perforated black box on the fire wall with a multi wire connector on its bottom side. The logic board's solder connections crack and its logic becomes erratic and illogical.
These are sold rebuilt for about $100.
Then there's the servo, that cursed monster under the hood. These are sold rebuilt for $400 to $500 - I'm told that 20% of the rebuilt units fail in the first month so you may want to keep your old "core" until the rebuilt has proven itself.
I would normally say the amplifier is suspect but since the servo hasn't operated in two years it may be the offender.
There's a new alternative which I'm going to try. Performance Products sells a digital servo replacement kit for $700 that does away with the amplifier and the servo. It uses modern components. Its inventor reverse engineered the old "system" and figured out how to replicate its functions using modern parts.
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Q wrote:

Not having heard this one, what happened with the vacuum pump?
Rochelle 1979 Frankenbenz (240D with 300SD engine)
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