300se Leaking Antifreeze
 

I have a 89 300se with 193k on it. The other day, I was under the hood checking oil, etc. and I noticed a spot of antifreeze on the garage floor. I checked around to see if I could see anything leaking in the motor such as hoses, waterpump, etc. and found nothing. I went on about my business and have been watching it for the last few days. Everynight after the car is brought into the garage and has sat for a while, you can look under the car and there will be a spot of antifreeze about the size of a softball. Last night I crawled under the car and tried to look from underneath. All I saw was a bead of antifreeze that looked like it had come from the front portion of the oil pan and had settled under the pan and there was where it would drip on the floor. In the past when I have had waterpump problems on other cars, the antifreeze will show up around the waterpump itself and a lot of times will splatter on some of the hoses. Can anyone tell me if I am looking at a new waterpump or could it be something else? Also, is there something else I can check to pinpoint the problem?

When the water pump on your 103 engine fails, the fluid finds its way down the left side of the engine and drips off the left pan rail toward the front of the engine. You cannot see the weephole of the engine very easily, if at all.

If that is where the leak is coming from, it is almost certainly the water pump. The water pump on these engines is a real challenge to change.

Hope this helps,

Just as Larry says. The dribble starts at the snout of the water pump behind the pulley, continues along the bottom surface of the pump then towards the block, hits the block below the water pump, travels rear above the oil pan mating surface, then to the ground below the engine mount. You won't see a trace of the leak anywhere upstream of the water pump to block mating surface so it's tempting to think it's a bad o-ring.

Remove the serpentine belt and tug on the pulley. If there's any axial or radial play whatsoever, it's time for a new water pump.

If your fingers are small enough, see if you can feel wetness along the lower part of the snout of the water pump behind the pulley.

Sixto
95 S420
87 300SDL

Timing of the Waterpump
 

Larry, how fast do they normally go when they go? It has been doing the drip for a couple of weeks and the level in the resevoir seems to lead down very, very, slow. Where would be the cheapest place to buy a waterpump?

Scott

when you take the pump off, make to spin the idler pulleys and replace the noisy one(s). belt tensioner, shock, look at them before you take it apart. good luck, chuck.

Thanks for the post. I have been seeing a small drip spot under my normally dripless 300se over the last 2-3 weeks. One under the front and one further back by the pan. Because of the red tinted color I was beginning to think it was two leaks. One coolant in front and one tranny in back.

Now I have a glimmer of hope it might be one problem.

Not a good problem but one nevertheless.

the red drip near the pan probably is atf. haven't seen red coolant in a benz. good luck, chuck.

Do a search on 'm103 "water pump" and read up on it. Mr. sixto has some info.

I just finished this task. I started last week and finished today, due to the cold weather. I have three cars so I could take my time.

I removed the radiator. It's not necessary but it makes for more room. It's a plastic radiator so watch out for breakage, esp the AT lines.

There is an AT coolant pipe attached to the bottom of the radiator so watch its placement.

I could not remove the viscous fan drive so I removed the blades.

I was not able to remove the tensioner bracket so I just moved the tensioner out of the way to remove the lower WP bolt.

Unbolt the PS pump and move it out of the way.

Remove the tensioner shock as well.

Sixto uses a 1/4" drive for the top rear bolt. My WP was the original and the u-joint broke, I used my 3/8" drive. It's a PITA.

Use some grease on the water pump o-ring to keep it in place.

Get a new short hose from the pump to the head pipe.

You will also have to remove the distributor cap to loosen the heater pipe cap screw. I have to replace my cap, rotor and wires, the coil wire is charred at the cap.

All I have to do now is add coolant and check for leaks.

I'm going to replace all my hoses, overflow tank, radiator and overhaul the mono valve.

Whew! What a job.

OR YOU COULD RENT A COOLING SYSTEM PRESSURE TESTER AT AUTO ZONE OR OTHER SUCH PLACE.

THIS DEVICE ELIMINATES THE GUESS WORK.

SORRY FOR THE UPPER CASE. IT'S LATE & I'M TOO TIRED TO CORRECT.

Water pump for sure. You have about a month before the leakage gets serious, maybe more, but probably not less from my experience on the TE.

Water pump change is about 6 hrs. I'd plan on a new tensioner, and if the visco clutch is covered in sticky oily crud, put a new one on (or refill it) while you are in there.

Watch the tensioner when you release it -- if the hub doesn't move back to the start mark, it's shot and you will have to replace it. I'd get one, just in case, although they are NOT cheap. Better to have it and not need it than not be able to finish the job til you get it!

If you've replaced the tensioner recently, this isn't a problem.

When you get it all back together, fill the engine by filling the overflow tank til it won't take any more coolant, then squeeze the upper radiator hose flat. Squeeze the small line to the overflow tank shut and release the upper rad hose. This draws coolant into the radiator and helps pull it through the heater core and head. Repeat with filling as necessary until the upper hose is full and the level in the tank doesn't drop.

Run to operating temp with the heater on full blast, then cool and repeat the hose squeezing. You may still need coolant later as the rest of the air works out, but the above procedure will prevent you overheating the engine trying to get coolant into it.

Peter

The M103 has bleed ports on the head. There are a couple of bolts on the surface of the head beside the valve cover rim above where the stub hose from the water pump meets the head. They take a 14mm socket. Some engines have a thermo-vacuum switch in one of the ports.

Consider filling with coolant before fitting the thermostat to minimize the amount of air trapped to that height.

That lower hose looks like it'll hold a quart of air.

With the right hex key you don't have to remove the distributor cap to remove the heater line clamp.

Sixto
95 S420
87 300SDL

True, but an inspection is helpful. That's how I found I need a new one. I could do what someone I know does, he puts his Volvo 240 distributor cap and wires in the dishwasher. He says it works every time.

Yes, with the right hex key you don't have to remove the distributor cap, but note that you don't have to remove that bolt, just loosen it. The tab on the pipe is slotted, so you loosen the bolt and the other attachments for the pipe and slide it out.

There was a mention of six hours. It might take that if you completely strip everything, but even if you don't have the special Snap On flex socket extension, it shouldn't take six hours. You can use an extension, a universal joint with tape on it to stiffen it and you won't have to remove everything.

The special Snap On Tool is over $40, but they didn't have one in stock via the website and the Snap On man didn't have one on the truck when I needed to do the job. Maybe they have it in stock via the website now. I think that the number is something like FLXM 13.

Don't try to stretch the water pumps life. You're expensive engine is at risk. Just replace the pump and be happy.

My $0.02,

Larry:

With the proper tools (I borrowed them from my friend), it took me exactly 6 hrs from parking the car to starting it to test the seal. Would have been faster if I'd known that the belt tensioner shock pushes the belt pulley so far over.

I'm sure it would be somewhat faster the second and third time, but I'd expect someone who has not done this before to take just about 6 hours.

The water pump bolts are a little fiddly, but can be reached with swivel sockets or extensions without too much trouble.

Peter

I finished mine this morning. I added the antifreeze, started the car and looked for leaks. No leaks, the car warmed up fine but I think I need a new tensioner. So I'll have to do that too, and the idler on the passenger side of the engine.

That was a real chore.