First time here hoping that someone can help me with my problem. I had a 94 SL500 that was my daily driver for many years. I put it together from a basket and it was relatively trouble free. I replaced it with something that my ancient frame could get in and out of easier and it sat in my side yard for over two years. I finally gave it to my granddaughter as a throw away first car. BIIIIIIIGGGGGGG mistake. I accept full responsibility for not checking it close enough before I gave her the keys but the first thing it did was to blow the heater hose behind the left cylinder head. She did not realize what was happening and barbequed the engine. Found a used engine and put it in. While I was trying to get it running and back on the road the electrical problems started. ASR light and throttle in limp mode, A/C control problems, heater core and an whole host of other problems. Over the next 5 months I finally got all the gremlins fixed ( I thought) drove it down to the tire store to get the leak in the left rear fixed. It cracked the plastic radiator and took out the head gaskets. Replaced the head gaskets, put in an all aluminum radiator and now I have a heating problem I cannot figure out.

Here is what I know. For some reason the left side of the engine will not fill with coolant unless I disconnect the heater hose at the rear of the left cylinder head and force the coolant across. On surface streets it runs consistently at 80-90 but as soon as you get on the freeway the coolant temp is well over 100 in less than a minute, get back on the surface streets and it will settle back down to 80-90. I don't think it is head gaskets because 1, it is fine on the surface streets and 2, it is not blowing the coolant out. First thing that went through my mind was thermostat so I tried to pull the t stat housing and two of the three cap screws seized in the water pump. In about three or four days when my blood pressure comes down out of the stratosphere I will pull the pump and probably replace it along with a new t stat.

In the mean time does any one have any thoughts on what the problem might be.

 

The new head gaskets are either on wrong or are wrong for your non-original replacement engine that you think is the right engine for the car.

 

Gaskets can not be put on the wrong side, the left side gasket has a much bigger cam chain hole, and they match the gaskets that came off exactly, hole for hole. The engine part number is the same as the engine that came out. Good thought though.

 

For anyone that has a similar problem I finally got back under the hood and pulled the water pump. Got the t stat housing off and found that there was no print from the thermostat on the spot to block off the internal passage. Put the stat in a pot of water on the stove and turned on the fire. Stat opens late and does not open enough to close the internal passage in the pump. For over 60 years I have been doing quickie stat checks by holding the upper hose and checking the temp gauge. I am here to tell you that it does not work on a Mercedes, at least of my vintage, because the thermostat is entirely capable of working partially. Put the pump on off of the original engine because it had no broken bolts seized in the aluminum and I know that the pump only has about 20,000 miles on it. put in a new stat and the engine is running steady below 80, A/C on or off. Just thought I would mention this because It cost me a lot of time and effort to figure out. Maybe it will save someone the same effort.

 

I found out my thermostat wasn't fully closing (to warm the engine) until I went on a trip north last winter. I live in FL and it never got cold enough for me to find out.

In the north the engine would not warm up fully and the CPUs (V12 engine, 2 management computers) kept the fuel curve rich, not so great mileage, I changed out the thermostat in Virginia and the engine warmed up properly. I never had a thermostat stick open.

Good thing you still had the old engine to forage the water pump AND thermostat for the A/B comparison. So the new setup wouldn't fill or circulate the left cylinder bank? Tricky.

These cars are never dull. Cheers on your thought process and repair.

 

You were lucky that it was apparently stuck in the full open position if yours is plumbed like mine. Had it been stuck in between it would have hot spotted the engine all over the place and you probably would have been doing head gaskets at the very least. Yours is three years newer so possibly they had figured out that it was not such a good idea and changed the system.

Still haven't figured out the left bank fill. When I got the pump on still had to take the heater hose off to get it to fill but once full with a good t stat it runs at a lower temp than the original engine ever did. As long as it gives my granddaughter good service for a few years don't see why I need to figure it out.

Now if I could just figure out the AIR pump issue and get the CEL off.

 

I swapped out my secondary air pump, associated air filter plus soft hoses a few weeks ago. I was planning a new thread on the repair, but something else popped up.

 

Lucky you. I replaced it twice and it didn't get better. Afterwards I pressed the big spring completely together about 10 times, since then the thermostat has been working. I suspect the new thermostats have too much bias.

 

I am not sure that luck has anything to do with it. After 6 months of chasing obscure problems on this accursed car that no one has ever heard of I may have shed enough blood to satisfy the Mercedes gods (or devils). In addition I have discovered that using non Mercedes parts when possible seems to be a good idea. The t stat is a Beck Arnley.

 

In early days it was a good idea to find out what the original facturer is and buy original parts direct from then. More and more, this will not work anymore. The OEM of the thermostat is WAHLER, sold 2014 to the proud of USA BorgWarner. You get what you pay for.

 

I recently told a new supplier of the cabin plastics that sometimes I think the car is haunted. Haunted sounds more sporadic rather than cursed.

Aside from the replacement plastics, they also made me a beautiful wooden tambour door slide handle to replace my original broken brown painted plastic one on the console.

 

Is the handle really made of plastic? Mercedes has always had the talent to make wood look like plastic.

 

The OEM handle is hollow black plastic and painted a dark brown.

The 2 attachment points are surprisingly fragile and easily damaged. Mine was bad from the beginning and I tried to repair it with epoxy on the backside, but it still never fit well because there are two EVEN more fragile projections from the attachment points that help locate the handle on the tambour slat. When I made the original repair to the plastic, I didn't have any brown paint and just left the handle as it was with most of the paint worn off.

The new handle is well made and the contrast to the dark walnut burl makes it stand out for easy recognition. The camera flash makes the wood look lighter than it really appears.


Attaching the new wooden handle.

Finally, a snug fit and a handle of one solid color.

The original and new handles.

 

I recently told a new supplier of the cabin plastics that sometimes I think the car is haunted. Haunted sounds more sporadic rather than cursed. (mayhunt)

Considering what I have gone through on mine for the last 6 months I will stick with cursed.

As for the plastic I will echo what many before me have stated. Why is it that a car that cost that much new is loaded with cheap and fragile plastic parts and self destructing wiring?

 

According to legend, the insulation material of the cables was changed at the request of the California environmental authorities. The original material lasted too long and degraded too slowly. After that, the material didn't last long enough, the rest is history.

The plastic parts are up to 30 years old, I can't compare them to other makes and their plastics. But: I like the handle, that gives me an idea ...

 

Although I like my current wooden handle, I advised the seller to choose a harder and darker wood like American Black Walnut.

Ideas! That's one of the reasons why I posted the picture. I thought it was a novel solution to a mildly troublesome original part.

I hear you on the wiring and plastics issue. Those are 2 additional reasons why I chose a 1997 and a SL600 with the Exclusive Leather interior (less shrinking vinyl). Now all I have to do is swap out my tonneau cover for leather (like I did recently for my slowly flaking roll bar cover) and all vinyl will be purged from the interior. The remaining plastics are another issue.

 

If legend is correct why amongst all the vehicles sold in California both foreign and domestic, is the only one with disintegrating wiring a Mercedes?

 

I think I read something about a stupid environmental regulation the reason why the wiring is able to crumble, but my guess mercedes overengineered the biodegradability

 

My guess is that the legend was started by Mercedes so they would not have to take responsibility for the wiring. Instead they will sell you out of the goodness of their hearts a new loom for $600.00. At least that is what the tariff was when I needed one. I purchased $100.00 worth of wire from R.I. wire and in 4 afternoons after work rebuilt the loom. It is still on the car and working fine. I am still using the leftover wire from the loom rebuild.
I was in the business up until 2000 and I never heard of the EPA getting into wiring insulation. They are responsible for a ton of other ridiculous regulations but to the best of my knowledge wiring was not among them. If you think about it why would they want wiring insulation to disintegrate and possibly cause an unknown number of dangerous conditions by shorting out. I mean not even the EPA is that stupid.

 

...but my guess mercedes overengineered the biodegradability.

http://www.mercedesdefects.com/