[W126 Coupe] 420 SEC coolant system problems

[Dick Spellman]

Welcome Oisin.

That sure sounds like your thermostat is firmly stuck in the closed 
position where you are only reading a temp of 40-50 C.   Do not drive 
the car to your mechanic until you do the following.  With engine cold, 
remove the bolts securing the upper radiator hose fitting to the water 
pump.  Now remove the thermostat, keeping the rubber seal.  Replace the 
rubber seal followed by the upper hose fitting and bolts.  Replenish the 
coolant level and drive to your mechanic.

Or purchase the correct thermostat and new seal for the car and do this 
job your self in 15 minutes simply replacing the thermostat and noting 
that the little weep hole in the thermostat rim (flange) should be 
located at the highest point of the engine.  Your choice.  Either way 
when done have a pint of Harp on me.

Regards,

Dick

Oisin Margey wrote:

>  

> Hi everyone,

>  

> i'm Oisin and just joined, nice to meet you all. I'm Irish, living in 

> Dublin.

>  

> i've just got myself a beautiful 1990 420SEC, 76k FMBSH and 

> unfortunately am having problems already !

>  

> Yesterday after being out for a run for about an hour i started 

> hearing a slooshing / churning kind of a noise which

> seemed to be coming from the area in front of the driver, i could only 

> hear it while stopped at traffic lights,junctions etc.

>  

> At this point the temperature guage was at around 40-50 degrees, the 

> oil pressure was at the top of the guage at 3, so i think normal

> for both of these.

>  

> When i got the car home i sat and listened to it for a few minutes 

> with the driver's door open. Next thing steam starts

> escaping from the corner of the bonnet by the driver's wing mirror and 

> through the hinge area of the open door, then

> a liquid started pouring onto the ground from, what appeared to be 

> under the driver's door, the liquid was green and i

> believe it is the anti-freeze.  Thinking about it now the churning 

> noise could have been a boiling sound. 

>  

> I let it cool for an hour or so and brought some water to fill the 

> head tank for the radiator. ( i think this is the correct name ).

>  

> It filled up but if i waited a few minutes i could always put a little 

> more in, looking through the plastic tank it seemed to be about 3/4 full.

>  

> This morning the water level in this tank had dropped to about 1/4 or 

> less.

>  

> The car itself has only done about 5k in the last 5 years but has just 

> had a service with new plugs, leads etc. I'm hoping

> this is just some hosing or other consumable which may have perished 

> over time due to the car not being used regularly.

>  

> Any ideas ? Do you think it'll be safe for me to drive as far as a 

> mechanic ?

>  

> thanks

>  

> Oisin

>  

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