Hello I just got a 450sl and have a few questions - PeachParts Mercedes-Benz Forum

78 450sled · #1 02-04-2007, 09:17 PM

My name is Dave and I just picked up a beautiful 78 450SL yesterday. I traded it for a 1992 Blazer. Go figure. I have one other Mercedes. It is a 1959 190D and it is world apart from this one. I have two questions. What temperature do these engines run at normally when crusing at 60 or so ? Mine runs a little below 100 on the gage and it seems a little high to me. What temperature is the electric fan suppose to come on ? I haven't seen it run yet and I was wondering if it works. My next step is to get a manual so most of my questions can be answered. I have 10 other cars but this is my first roadster. I have always wanted one and I love it....

page62 · #2 02-04-2007, 09:30 PM

Congratulations, and welcome to the wonderful -- and occasionally frustrating -- world of SL ownership.

Is your car US-spec or gray-market? US-spec 450SL's have temperatures marked in Fahrenheit (0-125-175-225). It sounds like yours has Celsius markings...

How is your oil pressure gauge marked? Is it 0-1-2-3, or 0-15-30-45?

78 450sled · #3 02-04-2007, 10:19 PM

MIne has Celsius markings and it runs just below 100. Is this within the correct range ?

Walrus · #4 02-04-2007, 10:46 PM

Quote:

Originally Posted by 78 450sled

MIne has Celsius markings and it runs just below 100. Is this within the correct range ?

Without opening a can of worms, I'm gonna assume all things equal and advise your temp sounds fine. Not knowing anything about your location (?), guessing you wern't pushing the ole gal hard, and you were not running the A/C, I'd expect 80-95C to be normal, with minor excursions above 100 not unheard of. Now, if it was 40F or colder outside, you were babying her, and the heat was on full-bore, I might be a bit concerned with the temp near 100.

al76slc · #5 02-05-2007, 05:59 AM

10 other cars... sweet.

Test the antifreeze mix. Mine consistently ran hot until I drained and refilled with 50-50 using MB coolant. I also use Water Wetter. I can't say which has worked, but temperature has stayed lower since (16 years).

If yours is gray market, does it have cats? If they are under the hood, they will be a big source of heat.
Al

page62 · #6 02-05-2007, 08:37 AM

Quote:

Originally Posted by 78 450sled

MIne has Celsius markings and it runs just below 100. Is this within the correct range ?

Does the temperature rise to 100 from start...and stay there? If so, your car probably has a 100 degree (C) thermostat. So this would be normal.

If it makes you nervous, 80 degree thermostats are available.

78 450sled · #7 02-12-2007, 11:09 PM

Sorry I was out of town. Thanks for all the info . I'm still confused about what temperature the electric fan comes on. Does anyone know ?

On a different point does anyone know where I can get a LOCKING gas cap. I have searched everywhere and can't find one...

page62 · #8 02-13-2007, 07:43 AM

The electric fan comes on at 100 degrees C, or when the A/C is running.

The gas filler door is supposed to be part of the central locking system. In my car, it was disconnected...probably due to a failure of the system.

78 450sled · #9 02-13-2007, 11:13 PM

"The gas filler door is supposed to be part of the central locking system. "

I don't think mine has a central locking system. It's a 1978 and I don't see anyplace in the owners manual where it is mentioned or where it is attached to the gas filler door.

tjohn · #10 02-14-2007, 12:14 AM

They all have central locking. When you lock the driver's side door, both the gas filler door and, if you have set it to do so, the trunk, should lock. If they don't you have a vacuum issue.

Jim B. · #11 02-14-2007, 12:31 AM

Quote:

Originally Posted by al76slc

If yours is gray market, does it have cats? If they are under the hood, they will be a big source of heat.
Al

Only the '75 and '76 models had them under the hood. In '77 they were moved downstream so with the '78 he shouldn't be worried about that

#12 02-14-2007, 12:44 AM

Quote:

Originally Posted by 78 450sled

Sorry I was out of town. Thanks for all the info . I'm still confused about what temperature the electric fan comes on. Does anyone know ?

On a different point does anyone know where I can get a LOCKING gas cap. I have searched everywhere and can't find one...

Congrats on the sweet ride

The electric fan should come on when coolant reaches 100 deg/c, or the a/c freon switches on the a/c drier tell it to. A single prong switch near the upper rad hose gives a ground to the fan relay when the temp is high enough.

Does your car have a fan shroud? It should, and that will cause the elevated temps if somebody lost it along the way.

Retarded ignition timing, or slightly plugged radiator, or bad/wrong thermostat are more likely causes. I mention timing because someone may have retarded it, in order to use cheap gas.

One last, and remote, thought, the guage is electric, so a ground problem or loose connection may show incorrect temps.

As for a fuel cap, try a Stant catalog and remember that there isn't much space between the standard cap and the filler door.

78 450sled · #13 02-14-2007, 12:50 AM

Thanks but I have tried Stant and they don't even list a 450SL. I have only had the car a little over a week and I'm still learning about it.

#14 02-14-2007, 01:37 AM

It's a long shot, but the 113 chassis cars(1963-1972 230SL/250SL/280SL) came with a optional locking cap that will probably work.

Try calling these people, they probably can tell you for sure, and they will know where to get a 113 chassis locking fuel cap.

http://www.millermbz.com/

Tomguy · #15 02-16-2007, 10:35 PM

Erm, just so I know, was some change made on these 4.5 engines I am not aware of?
Thermostats are 75 or 80 - no such thing as a 100°C thermo to my knowledge. That's boiling water. 450 engines are supposed to run right at 175°F like most other MB engines. My 4.5 only gets up to the 212 mark when I am in HEAVY traffic and idling on 85°+ days. This is why 175°F/80°C marks are in the middle of the gauge. That is where these engines were intended to run. The fan comes on at 100°C for a reason. You would never have a 100°C thermo AND a 100°C fan - your fan would never stop running.

No matter how hot it is outside, a 4.5 with a proper cooling system won't go much above 175°F (and never 185°F) on the highway, even if you cruise at 120MPH+ for an hour. Ask me how I know

You may need a new thermostat. You very likely need a good coolant flush and new coolant. If it's green, it's garbage. If it's red, it's garbage. Put in Xerex and be done with it!