Hello all,

Since a while now I have air in the heating system. If I turn on the heater, which seems to work fine, I can always hear the airbubbles in the system. I have tried to get all the air out of the cooling system, even by slightly lifting the front of the car, but I do not seem to be able to get rid of it. While being at my Benz shop on other business I aksed how they bleed the system for air and explained why I asked. The technician there told me that this is usually caused by a faulty auxiliary water pump.
I have been reading up on this part in these forums and it sounds like a plausible story. The only thing I could not get out of the threads that I read so far is the location of this pump.
I drive a 1993 300e 2.8 24V (M104 engine). I do have something that looks like a swith mounted on the firewall just in front of the battery (when standing in front of the car). It has two cylinders (2-3 inches high and alloy colored) on a plate that seem to connect to the heating hoses. I am not certain which part this is but it does not really look like a pump. Where would I find the pump in this car? Would anybody have, or know where to find, a picture of the part and it's location?
Thanks a lot,....not for the first time,
Marc

To begin with, the gurgling sound in the dash after starting the engine is normal.

Secondly, the aux pump is on the frame rail below the radiator reservoir tank and slightly in front of it.

Good luck,

Hello Larry,

Thanks for the fast reply, I'll look for the pump first thing tonight.

The gurgling sound in my case stays also after a longer drive. In fact, just finding and maybe fixing the pump does not answer all my questions or issues. The main question should possibly be: where does the air come from, how does it enter my cooling system in the first place?
I'll find the pump tonight and have a look.

Again thanks for the fast answer and greets,

marc

Do you have any oil leaks from this engine? Air should not enter the system. Given that this is a 104 engine, I would investigate the possibility of a blown head gasket.

Good luck,

Hello Larry,

seeing that this is a mercedes engine with slightly over 100 k miles the engine is well lubed by the oil that should be on the inside. I fear that the dreaded gasket will cost me money in one of the coming months. The water looks oil free and the oil is very clean. No signs of comtamination in both. Since I loose cooling fluid without finding it on the floor it could very well be a haedgasket that is failing. But since most Benz engines will run for a long time while leaking oil and it is an expensive job I tend to postpone as long as possible. I once pressurized the cooling system and looked for traces of leaking fluid and could not find any ( I really climbed in and under the car to find something) and am therefore not in a hurry.

Greets,

Marc

Check your water pump. These things have a nasty habit of leaking at the seal when they fail BUT they only leak when the engine is hot consequently the coolant is burnt off the hot engine. You end up seeing nothing but your coolant keeps disappearing!! Look for the tell tale sweet smell of coolant...unmistakeable for anything else.

Hello Yal,

The unmistakable sweet smell of coolant is around. But at a certain point I focus on it soooooo much that I smell it everywhere. You could be right about the pump, such as the previous comment about the gasket. The former owner told me that the pump has already been renewed once. Since all his other stories checked out I have no reason to not believe him. I will check on the pump though. There is white deposit on the pump although very little and with the wet weather I live in it could be anything. If the engine is hot and I have her in the garage Imight be able to see leakage. IŽll double check the seals and see if they look new or if some joker used liquid sealer.

]Thanks,

marc

I agree with Yal that the leak is at your water pump. I was losing coolant and couldn't find any on my garage floor. It was leaking out when the car was running, and would evaporate before it would leak on the garage floor.

On my last car (a Nissan) I got two bad water pumps in a row from the dealer that broke within a year. The third pump was the good one.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Hello All,

I have replaced the cap on my expansion tank, let's see what this does. This weekend I need to check out the aux water pump and the main water pump. Since I am not too much of a mechanic I will do a visual to start with. To inspect the aux I need to remove the air filter housing because my aux pump is plaved below it. For the main pump I ned to remove the bottom plate so I can see the bottom side (hopefully) and inspect for residu or water drops.
Since I have a pretty nasty water gurgle in my heating system I would tend to suspect the aux pump. Worst case scenario is ofcourse the head gasket. With over a 100 k miles on the engine this one is also supposed to be suspect.
The engine never overheats though. Even in hot summer weather I can stand in traffic jams or stop and go and the engine does not go over the 100 degree mark. So I do not suspect hot fumes entering the cooling system. I expect the pressure in the combustion chambers to be higher then the pressure in the cooling system so it would be more likely for fumes to enter the cooling system then for coolant to leak away through the combustion process. Am I right in this last assumption?

Thanks and al have fun driving these nice machines,

marc

Hello All,

This morning I needed to top of the coolant level again. While driving in town with my window open I passed a wall and got the scare of the day listening to a loud ticking ccoming from my car. Inside the car it was impossible to hear. I plled over and walked around the car. Standing next top the driver door the clicking came from under the car. I popped the hood and heard a definite rythmic ticking. It is the sounds the valves make if they are icorrectly set. Trying to pinpoint the sounds I think it comes from the waterpump area. I could also hear the sounds of a belt that is hissing. I stopped the engine and pulled the flywheel that drives the pump. I could feel, just by puling it, some play. I am not certain if and how much play is needed or allowed on these pumps but can I assume that this sounds like a pump that is facing its maker?
When driving off afterwards the clicking was gone or at least much less and drowned in the normal engine sounds. There was still the sounds of a belt that was sort of hissing. The belt is older and its near freezing point out so that is not too worrysome.
A ticking waterpump is definitely not a good sign right?

Any suggestion or answer is welcomed.
Greeets,

Marc

So we're dealing with multiple problems here. The gurgling and your talking about air in the system sounded like a head gasket problem and could still be that.

The leak and noise is obviously a different problem. You need to pull the belt so you can spin all the accessories to see what is loose or worn out. You've already found the water pump to be a probable culprit, but don't forget to spin everything while the belt is off. It is a good habit to spin all pulleys even if the belt is just being changed as preventive maintenance.

You'll know more once you've pulled the belt.

Good luck,

Hey guys, I think I can shed some light on the gurgling noise. In 1991 MB came up with a temporary cure for this. We were instructed to raise the front of the vehicle so that the expansion tank was the highest point in the cooling system (except for the top of the radiator). With the pressure cap removed and the climate control set to maximum heat, run the engine at 2500 RPM for at least five minutes. This allows the air trapped in the heater core to escape. I did it several times and it worked just fine. A short time later MB made available an air separator that was to be installed at the area of the heater hose near the firewall on the drivers' side. It was a very straightforward job that is easily within the ability of most DIYers. It's been at least ten years since I've done this job so I'm probably missing a few details, but I'll check it out Monday morning when I get to work. As far as the auxiliary water pump being the reason for the air in the system, I've never heard of that before, but anything is possible.

Hello All,

yesterday I removed the Air filter housing because supposedly the aux water pump was placed beneath it. Well it isn't. There was nothing ther but a solid pipe. There is however a switching unit in the area of the battery. It looks like three cylinders on a plate. Two low ones and a higher one. (I'll make a picture and post it). I assume this is the aux pump. It is out in the open so easy yo test and replace. The clicking and the play in the pump dissapeared after running and shutting down the engine (????).

I agree that I am most probably looking at a head gasket that has seen better days. I'll consider taking the car to the Benz dealer and have them pressure test the system. I can not see any coolant laeking anywhere and as far as I can see the waterpump is dry all around. It is near freezing point ambient temperature here and even after heating up the engine there is pretty much white vapor coming out of the exhaust, but then I see so many cars do this in this weather so I am not certain that this is a tell tale sign of a broken gasket. I guess that just guessing will not provide with the answers I need so I will have to invest in a real test.
Wish me luck,

Marc

Hello All,

This week I was able to get an appointment with my Benz dealer. I explained the loss of cooland and also the loud ticking of the pump and the gurgling in the heating system. The aux pump I had already checked by applying direct current to the pump. It worked fine. According to the benz tech it hardly ever happens that the pump is not triggered. If something is off it is a busted pump. Not in this case though. I asked them to pressurize the cooling system and look for leaks. They called me after a couple of hours and told me that the upper hose on my radiator was leaking. I had not seen this happening so I sort of objected. They replaced it anyway. I then asked them to again pressurize the system and leave it like that overnight and still pay extra attention to the waterpump and the head gasked. They called back the following day saying that the system kept pressure over night and that there were no signs of a leaking pump or a drop of pressure. The mechanic was not really wiling to replace a pump since he could not see a problem with it (good service!!!!).
They took it for a few drives and pressurized for a third time. No loss of pressure. Topped up the level and checked the mix of coolant and water and told me to come pick up my car.
The mechaninc did stress to me to keep paying attention but all should be well. Then the big surprise,.....the bill....... 70 us dollars!!!!! I was more then pleased. So let's just hope that this has actually solved the problem. I never saw this hose leaking but then who knows.
If things go bad again I'll write the sequel in thius thread.
Thanks for all the help!!

Greets,

Marc

Hello All,

And ofcourse misery strikes again. The ticking is still there ( might be a valve though, I can't really pinpoint the location) and I am still loosing coolant at the same pace. After pressurizing the system for three times you would think they can trace the leak. Aparantly not. If there is no leakage while under pressure but I d o loose lots of coolant
(a liter on 200KM's) what could be an alternative cause? Anyone any wild ideas?

Thanks and greets,

,marc