230sl coolant loss problem

[wisnia07]

Gentelman,
I have a problem with coolant being spilled through the overflow pipe. After I turn the engine off, the pressure in the system is forcing down about 0,5 liter of coolant, and after some half minute, the coolant level drops down to zero in the expansion tank. It seems to me that when the engine is running, the extra pressure is somehow distributed within the system, and when the water pump stops the pressure increases for a while.

The ignition timing is 'spot on' with the 123 distibutor installed, the thermostat is new, as well as the coolant tank cap and radiator fan clutch. I got the whole system 'back flushed' and filled using these instructions - http://www.sl113.org/forums/index.php?topic=6385.0, so I'm pretty sure there are no air bubbles in the system. The engines temp is constantly around 180deg. The fuel/air mixture looks correct to me, every spark plug looks exactly the same. There is no extensive smoke from the exhaust and coolant and oil are not mixed.

My first thought was the blown head gasket, but then I should notice different deposits on the spark plugs or at least some white smoke.


Any hints appreciated! 

[ja17]

What is the history of this problem?  If you have just replaced your coolant, the problem might just be an "air lock" in the cooling system.

[wisnia07]

When I got the car, there were many issues with the engine. It was overheating, WRD was constantly on, the spark was weak and not in time (123 ignition helped here). Someone had pulled out the main thermostat, so there were something wrong with cooling before.
Now the engine keeps the correct 180deg and the last problem seems to be the coolant loss.

Yeah, I've changed the coolant and tried different ways of getting the air out. First I was filling it through the heater hose, and then with the engine runnig, I let the air out of the highest points in the coolnig system (WRD top hose and drivers side heater hose). The heating works very good, so I dont think that this is a problem.

Are there any other 'tricks' to make sure that the 'air locks' are gone?

[Benz Dr.]

Try a bottle of water wetter.

 You could have a small leak in your head gasket.

[rutger kohler]

Hi, I know the 230Sl coolant reservoir  is different to the 280SL but this is how I get rid of the air out of the coolant system everytime I refill my 280SL coolant.  

In the attached photo, the water bottle has the bottom cut out of it and I have wound thread tape around the cap thread so it is a tight fit in the inner diameter of the reservoir cap .

I mix up the correct amount of coolant and pour it in through the upended drink bottle.  The reservoir fills up with less than the full amount and I keep filling until the drink bottle is about a third to a half full. The engine is then started up and run on idle, when the thermostat opens there is a "burp' through the coolant in the drink bottle and the coolant level drops away. The rest of the correct amount of coolant can then be poured in and the drink bottle removed.  The engine is then stopped and the coolant reservoir cap fitted.

I had exactly the same problems that you had before i hit on this idea.  It seems the static head in the drink bottle is just enough to displace the air.  Do not fill the drink bottle over 1/2 full when starting the procedure otherwise you and the engine bay will wear coolant!


I have done this three times now and it works beautifully.

[Benz Dr.]

Drill a 1/8'' hole in your thermostat and it will self bleed.

[wisnia07]

Thanks rutger kohler, I will try your bleeding procedure. Maybe that would help!

I've just noticed on your photo, that there might be one more reason. My engine block is 230sl, but the head is from a 280. My coolant reservoir is from a 230sl. It seems to me that the two reservoirs have their tops mounted at a different level in the engine bay. Maybe I should have the reservoir for a 280 model???

And when it will be a little leak in the head gasket, do you think that re-torquing the head might help??

I will try to bleed it first, but I got a feeling there is something more happening. I will check it tomorrow and let you know!

Thanks for your help.

[Jonny B]

There is a discussion about coolant flush and system bleed in Pagoda Notes Vol 5 no 4.

One item is to park the car with the front higher than the back and open the coolant tank. The proper thermostat should have a small air bleed in the rim. The thermostat should be placed with this little air bleed at the front of the engine.

[Benz Dr.]

There is a discussion about coolant flush and system bleed in Pagoda Notes Vol 5 no 4.

One item is to park the car with the front higher than the back and open the coolant tank. The proper thermostat should have a small air bleed in the rim. The thermostat should be placed with this little air bleed at the front of the engine.

That air bleeder won't release enough air and sometimes you need to add a small hole to augment that process.

[Benz Dr.]

Thanks rutger kohler, I will try your bleeding procedure. Maybe that would help!

I've just noticed on your photo, that there might be one more reason. My engine block is 230sl, but the head is from a 280. My coolant reservoir is from a 230sl. It seems to me that the two reservoirs have their tops mounted at a different level in the engine bay. Maybe I should have the reservoir for a 280 model???

And when it will be a little leak in the head gasket, do you think that re-torquing the head might help??

I will try to bleed it first, but I got a feeling there is something more happening. I will check it tomorrow and let you know!

Thanks for your help.

A 280SL head may fit on top of a 230SL block but the coolant holes won't line up. On a late 280SE/A head you will have a lot of problems. Are you sure you have a 230SL block?

[wisnia07]

I'm pretty sure and I know it's a strange combo. But after reading this article http://www.sl113.org/wiki/Engine/CylinderHead, I'm still hoping it can work together.
My engine number is 127 981 - 10 - 001866 (230SL) and the head is 130 016 1101 (which is 280SE).  When I look at the engine bay photos of 230 and 280sl the coolant reservoirs are mounted in a different level.
Maybe having a 280 head, I shall use the 280 coolant reservoir?

[Benz Dr.]

I can't imagine how that would make much difference.

 Drill a small hole in your thermostat and that should help to fix your problem if it is an air lock. I can imagine however, that you may have a compatibility problem with your head, the head gasket, and your block. Any one of these things could be causing coolant leakage into places you don't want it to go.

[wisnia07]

I've went through the cooling system again, did 'a few' bleeding procedures to be sure about no air locks. I took it for a ride and nothing changed. I was still loosing coolant. It was late at night and on my way back home from the garage  I've had the last 'look' at the coolant reservior... and then I've realised that the overflow hose and the one going back from the top of the radiator were mounted the oposite way.  Quite a surprise from the previous owner - it took me while to figure it out.

So I've switched the hoses and went on the road again. This time with no overflowing coolant! It seems that I have finaly solved that issue.

Thank you all for your help!

[Cees Klumper]

Sometimes it's simple things .... Hope this did solve the issue but it sounds like it to me.