I've only owned my 1988 560sl for a few months now, so this is my first summer with it. The car has been running great until I drove it back from the mountains to Phoenix this week.
Problem #1
It was 110 degrees today and the car doesn't like it. I am having a hard time getting it started. It cranks but won't start for a long time, pumping the pedal seems to help. After it starts it runs fine, smooth idle etc. If I shut it down hot and try to restart it it fires right up. The ABS light is NOT on (I searched the archives and found the OVP relay ABS light thing) doesn't seem to apply. Any Ideas?
Problem #2
Until the weather got hot the engine temp was always around 80 degrees. Now that it's warm I've noticed the temp rising to 110+ degrees when climbing hills on the highway, turning off the A/C doesn't seem to help. It cools right down to 80-90 degrees on level ground. It also gets a little warm in stop and go traffic. I hear the electric fan (under the hood) come on when the A/C is turned on. The temp gauge in my C-280 stays at 80-90 degrees under these same conditions. Is this normal for the 560sl or do I have a problem?

Ken

It's common to lose radiator heat transfer capacity with age and mileage. The degradation will be more rapid if "green" antifreeze is used as the silicates and other inorganic salts will tend to build up deposits in the aluminum radiator tubes and form a thermal barrier.

You may be close to having to replace the radiator. I doubt if the average 15 year old car that has received indifferent cooling system maintenance would make it through an entire Phoenix summer. A fifteen year old radiator probably has in the range of 10 to 50 percent loss of original heat transfer capacity depending on the quality of coolant and frequency of coolant changes.

The best coolants to use are MB brand, Zerex G-05 or Havoline Extended Life (Dexcool). Prestone also offers a licensed Dexcool.

The first problem may be vapor lock, even if the accumulator and pressure regulator are still in spec 110 ambient temps could cause some vapor lock as underhood temps could reach over 180 after five to ten minutes of hot soak in the sun.

Flooring the throttle might be the best response to lack of hot starting as this will call for maximum fuel flow and purge the vapor more quickly.

Duke

Duke
I just looked at the coolant and it is green. Would flushing the system and refilling with the right stuff help or is it too late?
The starting problem is worse when the engine is cold (thats a relative term in Phoenix) If I try to restart it right after I park it it starts right up.

Once the deposits form they're virtually impossible to remove by flushing, so changing coolant now won't have any effect. You should start shopping for a radiator. It's probably made by Behr and available through the aftermarket, which might be cheaper than the dealer.

I believe there are also some outfits that can remove the plastic side tanks, which would allow the core to be "rodded out", and then install new tanks.

Your starting problems are unclear. Is it hard to cold start in hot weather, cold weather - hard to start after a hot soak, what? Be more descriptive of the conditions where it starts easy and starts hard. Electrons are cheap!

Duke

Duke

I'll start hunting for a radiator.

Let me clearify the starting problem.
First thing in the morning it won't start. It cranks and cranks and won't fire until I pump the gas.
After reading your previous post I tried a different techique this morning. I put the pedal to the floor and held it there. I cranked and it fired right up.

Ken

Well, at least now you've got a workaround. It sounds like a flooding problem. How does it restart after a hot soak.

Say you shut it off from a fully warmed up condition and let it sit in the afternoon Phoenix sun for 30-60 minutes and then start it up.

Duke

Duke

When it's heat soaked it doesn't start without pumping the gas.
I'm assuming this is just vapor lock (my airplane does the same thing). The two strange things are:
1) never had this problem until this week.
2) If I shut it off hot and immediatly try to restart it it fires right up.

Ken

Hard starting after a heat soak could mean flooding due to leaky injectors. If it's reluctant to start after a heat soak due to flooding, flooring the throttle should help.

Not sure why it starts easier with the throttle wide open when it's cold, unless the flooding is not clearing out overnight, which is possible.

Could be the problem is caused by your recent high temps or it could be something on the car. Take some resistance readings of the KE engine temperature sensor at cold and operating temp and see how they compare to spec.

Immediate start after a hot shutdown is consistent with flooding as the fuel from a leaking injector will take some time to build up and cause a flooded condition.

Duke

The hard starting needs to be addressed.. However on most of the cars when the temps are over 80 they take 6 to 10 sec. of cranking... I would reread the drivers manual and follow it exact.. One often forgets just what it says about that engine and often addresses any normal problems the engine has.. Odds are like Duke said.. leaking injectors.. however there could be lots of other reasons..


The temps..

110C to 115C on a hot day 90 F or above while setting in traffic or climbing steep grades is not as bad as some will try to make you think.....

Thermostats open full at about 107C or so.. So thats really about 110 for most of us to read on the gage..

Most MB fan clutches come in at 104C to 110C so under about 110ish for most of us the fan clutch is not working..

The electric fans come on at about 100C on low and go to high about 107C to 115C.. so if your car is one of those that runs things in the upper limits 110C to 115C is really where every thing really starts doing what it should..

Above temps are from a Mercedes Factory Manual and cover several models so your should be near those..

In general most of the newer cars tend to run 100C ish to 115C in temps above the upper 80sF... Newer meaning 88 and up...

I would change the Thermostat and change the anti freeze.. Never a bad thing to do any way..

After that you can park the car nose in to a wall so it gets little air flow .. back of garage or side of house on a hot day.. turn the AC on... Roll the windows down so you can hear whats happening... Run the car up to temp at about 2000 to 2500 rpm..

At some where around 100C you should hear the electric fans come on low... about 105C to 110C you should hear the roar of the fan as the fan clutch kicks in... and soon after.. 110C to 115C you should hear the electric fans kick in to high.. ..

If all this happens at temps some where in that area.. Odds are things are normal..


I have no clue why every one thinks their car should run at 80F.. when the thermostats start to open at 85C to 90C.. If your car runs 80ishF it means the thermostat has failed or you have no need for the radiator and fan system as none of the water is going thru it.. Just running thru the engine.. 100C to 115C is normal for a normal working car in warmer temps... and if your car runs under about 90C in 75F plus temps.. Replace the thermostat.. in winter much of the engine cooling is done by the car heater as it is inside the closed engine cooling system and often the thermostat never opens.. thats why the cars will run 80ish C... However in the summer things should start to work normal... 90C to 115 C..

Ken


__________________