coolant

[davids]

1971 280sl coolant constantly coming out the overflow tank when running?

[Peter van Es]

Either you've overfilled, or you have a vapour lock, or a blocked coolant line, or a more serious problem.

Peter

[bogeyman]

Have you checked the cap?

[davids]

with the cap off ,after just a few minutes running ,coolant flow is steady coming out the overflow until i shut car down .temp rises very quickly.

[J. Huber]

First of all, if temp is rising -- do not run it for long. Obvious but must mention it.

It sounds like maybe the thermostat is shot? or there is some kind of blockage. What is your radiator/maintenance history?

[ja17]

Yes, whats the history of this problem,?

[Benz Dr.]

I had the same problem after a rebuild on a late 280SL. It puked out a lot of coolant before I got it sorted out.
Normally I run just plain water in the engine while I'm doing the intital start up and break in. Since this was a winter build I had to use coolant - what a mess.

 I solved this by using a thermostat cover with a screw in cap - it may have been a plug for a 100 C switch. I opened the cap and let all the air release and it was perfect after that.
 With this problem the engine will over heat very quickly and the temp gage will spike in a minuet or two whereas a normal heating up period will be slow and gradual by comparison.

[davids]

new radiator,new water pump, just replaced thermostate again,pullled system apart to see if i hade a blockage,everything seamed well,but when i was flushing threw heater core water didnt seam to go threw very well,noticed the valve was half open , so i opened all the way then water flowed threw fine .put everythig back together now everything seems fine.but dont know if was a blockage or got air trapped in system ,because heater core was half open and water was not flowing threw freely. any thoughts. Thanks 

[ja17]

Hello,

Most likely a air lock.  The top tank of the radiator will become hot when the coolant begins to circulate. If the top tank of the radiator does not get hot, turn the engine off before it overheats, let it set, than add more coolant. Repeat until the radiator top tank gets hot.

[tel76]

When i recently first started the engine after refitting, i lost a lot of coolant due to airlock i overcame it for the future with this modification.
Remove the nearside heater hose on the heater radiator, (you could use the rhs but the lhs is easier to do) mark where the hose clip fits,drill a small hole in the top of the pipe,refit hose and clip but leave the hole exposed,fill with coolant and as you do so you will hear the air being expelled,when coolant comes out of your drilled hole push the hose and clip back on making sure the small hole is under the clip.

[Garry]

Eric,

what did you do to stop the end of the heater pipe from rusting now that it has the hole with unprotected metal there?

Garry

[tel76]

Hello Garry,
The pipe is brass,so no rust issues.

[Bill Sgro]

Should the expansion tank cap be on and the system be pressurized when trying to eliminate and airlock?

[Benz Dr.]

I tend to keep the cap off until all of the air is released from the system. You can also lower your running temp about 5 degrees by using water wetter. Sometimes that's enough to keep it in a safe range.