Mercedes E420 overheating

I've been looking to purchase a '92 to '95 Mercedes 400E or E420. My problem seems to be finding a car which doesn't overheat. The last two I test drove,
both had overheating problems or at least I think they did.
For example, I test drove a '95 E420 over the weekend. It was a one owner car with 88,000 miles on it and the seller confessed that the car had been overheated three years ago. The seller said that the temperature gauge had been pegged out and the car was towed in for repairs. The invoice from the dealer indicated the overheating problem had actually been "repaired" a year ago. What did the dealer do? They replaced the radiator and a couple of temperature senders. When I drove the car, it was a hot day with an ambient temperature of 95 degrees. With the air conditioning on, we got on the freeway. The engine temperature initially climbed to 85 C. Five minutes later, the needle was nearly touching the 100 C mark on a very gentle hill at 70 mph. On another slightly steeper hill at only 50 mph in heavier traffic, the engine temperature reached approximately 107 C. Descending these hills (and we are talking gentle hills) the engine temperature dropped down to 85 C. Exiting the freeway and driving surface streets at 35 mph to 40 mph resulted in nearly 100 C engine temperatures once again. And, yes both of the auxillary fans were running.
This is the second E420 I've driven with apparent overheating problems. In both cases the sellers confessed that the cars had been overheated and fixed. I've spoken to one of my local dealers and they have nothing but praise for the 420 engine. They tell me that fan clutches commonly go out on these cars but the engines don't have any special overheating problems. My dealer also tells me that the cooling systems on these cars was unchanged from 1992 thru 1995.
Should I be avoiding the 420 engine or do most of these things just run hot? Thanks in advance...
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I have a 420 and it does not run hot in my 99 S420.

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Mercedes E420 overheating Group: alt.auto.mercedes Date: Wed, Sep 17, 2003, 1:53am (PDT+7) From: snipped-for-privacy@aol.com (VCopelan) I've been looking to purchase a '92 to '95 Mercedes 400E or E420. My problem seems to be finding a car which doesn't overheat. The last two I test drove, both had overheating problems or at least I think they did. For example, I test drove a '95 E420 over the weekend. It was a one owner car with 88,000 miles on it and the seller confessed that the car had been overheated three years ago. The seller said that the temperature gauge had been pegged out and the car was towed in for repairs. The invoice from the dealer indicated the overheating problem had actually been "repaired" a year ago. What did the dealer do? They replaced the radiator and a couple of temperature senders. When I drove the car, it was a hot day with an ambient temperature of 95 degrees. With the air conditioning on, we got on the freeway. The engine temperature initially climbed to 85 C. Five minutes later, the needle was nearly touching the 100 C mark on a very gentle hill at 70 mph. On another slightly steeper hill at only 50 mph in heavier traffic, the engine temperature reached approximately 107 C. Descending these hills (and we are talking gentle hills) the engine temperature dropped down to 85 C. Exiting the freeway and driving surface streets at 35 mph to 40 mph resulted in nearly 100 C engine temperatures once again. And, yes both of the auxillary fans were running. This is the second E420 I've driven with apparent overheating problems. In both cases the sellers confessed that the cars had been overheated and fixed. I've spoken to one of my local dealers and they have nothing but praise for the 420 engine. They tell me that fan clutches commonly go out on these cars but the engines don't have any special overheating problems. My dealer also tells me that the cooling systems on these cars was unchanged from 1992 thru 1995. Should I be avoiding the 420 engine or do most of these things just run hot? Thanks in advance... ****************************************************** This is apparently normal for MB's and the temps will fluctuate quite a bit with the A/C on. Its only when temps start climbing towards the red that one needs to be concerned. (Mine did and the thermostat was defective). I also found a recommendation that coolant/water ratio be diluted to 45% coolant and 55% water in warmer climes, rather then the 50/50 ratio. Antifreeze has a greater absorptive heat capacity and will make your engine run hotter. Be sure you only use MB Antifreeze and filtered or purified drinking water. Also get a Antifreeze Hydrometer and check the ratio. Dealers tend to use 100% Antifreeze when making repairs (mine did) and I had to dilute the coolant. HTH
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I don't know if I would go so far as to say that it's normal for the engine temperatures to fluctuate quite that much. I've driven several mercedes models to high mileage and none of them acted that way unless their was a problem with the engine. I know mercedes published air conditioning service bulletins showing what temperatures different engines should be running at with different ambient temperatures. Some of the 420 cars I've looked at are off that chart. Mercedes cooling systems may be marginal in hot weather. However, when I see a 100 C engine temperature return within a few minutes of descending a long hill, I know the cooling system capacity has been exceeded. BTW I forgot to mention that the E420's I was looking at all had low water levels in the radiator expansion tank. Not below the low coolant sensor but low none the less.
Personally, I don't think it's a good idea to run any mercedes engine above 100 C for an extended period of time. But that's probably because I cracked a head on a mercedes which was never overheated.
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Some Merc engines run at a temp range 80-100c. If your drive the car on motorway, the temperature will probably drop to around 80-90c. As soon as you stop the car, the temp will go up but not more than 110c. The Antifreeze is to increase the heat capacity (boiling point) of water and also to prevent freezing in winter.
(VCopelan)

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hill,
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head
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A slight correction: heat capacity is not the same as boiling point. In fact, heat capacity is *lower* for a mixture of antifreeze and water than it is for water alone. http://www.tpoparts.com/questions/cooling.html explains it quite nicely.
Cheers
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snipped.............. I don't know if I would go so far as to say that it's normal for the engine temperatures to fluctuate quite that much. I've driven several mercedes models to high mileage and none of them acted that way unless their was a problem with the engine. I know mercedes published air conditioning service bulletins showing what temperatures different engines should be running at with different ambient temperatures. Some of the 420 cars I've looked at are off that chart. Mercedes cooling systems may be marginal in hot weather. However, when I see a 100 C engine temperature return within a few minutes of descending a long hill, I know the cooling system capacity has been exceeded. BTW I forgot to mention that the E420's I was looking at all had low water levels in the radiator expansion tank. Not below the low coolant sensor but low none the less. Personally, I don't think it's a good idea to run any mercedes engine above 100 C for an extended period of time. But that's probably because I cracked a head on a mercedes which was never overheated. ***************************************************** Perusing in other MB forum discussions I have found your temp concerns are quite common. However, having lower coolant levels in the expansion tank leads one to believe that there is another problem, such as a leaky head gasket, or a leak somewhere. I had a leaky water pump, but was apparent only after the car sat overnight and cooled down, when a small puddle collected under the car. If you really want to avoid the headaches you anticipate in the purchase of a used MB, I might suggest you find a Starmark MB at a dealership with an MB extended warranty. You will pay a lot more, but will have the peace-of-mind of knowing that for the warranty period, most problems and repairs are covered. One of the reasons most people get rid of a luxury car is that their having too many costly problems with them. 92 - 95 MB's (and newer models) have now become the most trouble prone and expensive to repair. For example, CU's current rec's say to avoid all 94-99 MB C280's! I recently spent $1100 to replace my water pump, belt tensioner assy, and acc. belt. Ciao!
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I may finally purchase a Starmark mercedes from a dealership. The problem is I'm trying to avoid buying a mercedes with rack & pinion steering and the '96 to present automatic transmission.
I'm told that the '96 and later transmissions which have electronic shifting also have a plastic bushing which replaced a torrington needle bearing. These transmissions don't usually live very long. I guess the post '95 S class cars still have the recirculating ball power steering?
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steering and the > '96 to present automatic transmission.
Just my opinion here, but I think that's nuts. The new trans is the 5 speed, best autobox I have ever owned. My W210 E-Class steers very well with R&P steering.
MC
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How many miles do you have on your 5 speed W210 E-class transmission? BTW I've owned plenty of cars with rack & pinion steering. They all drive fine and they all start leaking around 100,000 miles. I would be on my third rack & pinion on one of my mercedes if it didn't come with recirculating ball steering.
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I only have 61k on my car but many on the group go hundreds of thousands of miles with no trans troubles. As for the rack, no leaks yet but I have not heard of that being a common problem either. Now if you're talking about window regulators or electronic glitches......
MC
Writes:

speed,
BTW
fine and

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I've heard about lots of problems with the '96 and later 5 speed transmissions. Most of the problems involve the use of a plastic bushing instead of a steel torrington needle bearing on one of the shafts in the transmission. I've been told it's not uncommon for these transmissions to fail at 80,000 miles. I've also been told this is a problem by two different transmission shops and one of these shops only work on mercedes transmissions. One shop tells me they fit a torrington bearing from one of the earlier transmissions into post '96 transmissions. Does Mercedes have an extended silent warranty on these transmissions?
How many rack and pinion cars have you owned? I've owned BMW, Toyota and GM cars with R&P power steering. They all developed leaks around 100,000 miles. Perhaps mercedes is better than that?
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transmissions.
steel
I think this problem was solved in later years. I'm not a Mercedes tech but I lurk in the Merc boards all the time. Here is a quote from an MB technician:
"I've SEEN them (722.6 transmissions) go 300,000 miles without ever being serviced, so I know they can do it."

GM
miles.
My best experience with R&P steering would have to be my 1989 Mustang street/track car - 122,000 miles, probably 1/4 of that on the racetrack. Original rack, tie rods, PS hoses, ball joints, only thing I replaced was the bushings and I did that because I wanted urethane. No leaks, but the car has been garaged since day one if that makes a difference. I have had several other Fords with manual R&P and a Chevy Corsica with 180k on it that had the original rack too. I like the weighting of the rack steered cars better than the recirculating ball. I guess I've just had better luck than you with regard to leaks.
It sounds like you are caught in a very typical quandry. If you look at W210s (or any model) that are early in the build cycle then you will be the victim of the issues sorted out in the later models. Either way, it's a Mercedes so you're going to be spending money maintaining it. I would agree with the idea of buying a 124 but not because of the trans and rack. Because they were built to a higher standard of quality. Unfortunately, the fact that they are older can make them more troublesome. One way or another, the general consensus is that you should buy the best car you can afford up front because maintaining it can put you behind in a hurry. Look for meticulous record keeping. A warranty would be a great idea if you can get one. Good luck!
PS - I certainly would NOT call my E430 reliable - So far with two owners the following have been replaced:
CD changer Rear window regulators (three times) Harmonic balancer (common M112 & M113 engine failure) Lower control arm bushings Oil cap and filler neck valve cover gaskets cupholder door hood pad various instrument panel and other bulbs seat adjusters (another common E-class fault) rear shocks
That's all I can remember. I was very agressive with my local dealer when the warranty was about to run out and I insisted that everything be fixed. Hopefully the car will be reliable for a while.
MC
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Well, I did speak to a couple of transmission people and what they tell me is the 5 speed transmission problems actually began with the '98 model year. The 5 speed transmissions built up until July '97 are fine because they don't have that plastic bushing. Apparently, the plastic bushing is still present in some if not all mercedes remanufactured 5 speed transmissions. Repair parts are available to replace the plastic bushing with a torrington bearing but these repairs involve $1,000 of other parts. You can't just change out the bearing. I believe you are correct in that the later cars don't have these problems but I don't know when these changes occured.
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Power steering leaks is standard for all older MB. If your old Merces doesn't leak check the reservoir now!!
Keith Beast E14 4NS Docklands
Writes:

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Leaks from where? The steering gear box or the power steering pump? I own three Mercedes with recirculating ball steering and none of them leak power steering. I've checked the fluid levels. The lowest mileage car I own has 185,000 miles on it. One of my cars is approaching 265,000 miles. But that's nothing, I have a friend who drove his 1979 240D to nearly 400,000 miles on the original engine, transmission and clutch. His car didn't leak power steering fluid either.
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snipped: I may finally purchase a Starmark mercedes from a dealership. The problem is I'm trying to avoid buying a mercedes with rack & pinion steering and the '96 to present automatic transmission. I'm told that the '96 and later transmissions which have electronic shifting also have a plastic bushing which replaced a torrington needle bearing. These transmissions don't usually live very long. I guess the post '95 S class cars still have the recirculating ball power steering? ***************************************************** I wouldn't be concerned about the type of steering in such a heavy car, unless your going to race it! R&P types are more responsive and have less inherent play because of the design, then Ricirculating Ball type steering. You do get a greater 'sense' of the road with R&P, as with my last BMW and my current Supra, compared with my MB. The MB is geared toward a 'luxury' (softer) feeling. I can't tell you which models have R&P or RB. You have to test drive the cars and see which one 'feels' the best. At high speed driving, I would prefer R&P, which drifts less and is more responsive to small steering changes. I have 'heard' that the early models of the 5 speed auto were somewhat trouble prone, but they have been upgraded later on by MB goodwill (silent) recalls when brought to the dealer's attention. When I was shopping for a 500SL (which I didn't get, as it was impracticle for my needs, a 2 seater) my MB service advisor advised to get one with the 4 speed, a 95, fewer problems, then a 96. Anyhoo, Good Luck!
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