Car is getting hot at stops then cools once moving, but still a little
hotter than normal. When hot, at idle, fan looks like it's coasting,
thought it was the fan clutch, but radiator is cool in front of fan,
radiator is hot mostly at top and warm at sides. It is the radiator,
water pump (no obvious leaks) or a defective thermostat? Any educated
guesses would be appreciated? I could start replacing things, but
budget/time is tight and I'm doing the work myself. Anyone have luck
flushing a MB radiator? Thanks, Fredrik
Well, changed thermostat and still heating up with center of radiator
cold and outsider edges hot.... I think it's a clogged radiator and
not water pump... it's backing up at the coolant reservoir when hot...
Where can I get a deal on a radiator?
Forgot to mention car has 170K when I bought it and I'm not sure of
last owners maintenance of it... owners book shows oil changes
only....I noticed a lot of crud at the outer bottom flange of the
heater hose connecting to thermo housing...
Secret to loosening thermostat housing: with bolts removed, bang
housing at bolt holes/flange edge (ones you can see) with alternating
blows to rotate housing clockwise and counterclockwise, with a wood/
plastic dowel or stick. Six or seven hard blows, back and forth should
loosen housing. You'll notice slight shifting of of housing mating to
water pump assembly with each blow....patience will save the housing..
I drained radiator and back flushed it with hot water and could feel
heat on fins all around, thusly eliminating a clogged radiator... it
all points to a bad water pump cause car runs fine until car opens
thermostat, car gets hot, then the top return hose from radiator to
water pump is steaming/gurgling and backing up overflow reservoir
(water seems to not be flowing). Don't see any leaks by water pump??
Mmm... you done your homework. I am wondering if you have a blown gasket
problem... pumping air into your cooling system so that it can never be bled
If you have access to a cooling pressure tester (Autozone loans them for
free), make sure you properly release the pressure... then hook up the gauge
and pump it up to 15 PSI. See if the pressure stay there. If not, it is
Do you have alot of white smoke when you drive?
If you can't find the leak and the pressure keep dropping, then I want you
to start the car up with that pressure tester hooked up... keep an eye on it
while the car is warming up. Release the pressure before starting the car.
The pressure will rise to something like 25 PSI... and then hovers up and
down there... but if it above to 30 and keep climbing, release the pressure
from the the adapter and shut off engine. This would means blown head
There is another positive test for head gasket... the CO detector for
no... only some on cold days during warm up----60 degrees
Car will run normal temp for about 20 minutes then starts getting hot
(below red mark, but never in it, high white line) and when I stop
motor I hear a rumbling/gurgling (boiling) sound in hose from water
pump to radiator.
I'll check pressure gauge test next...
With engine running, I tried squeezing hose from water pump to
radiator and didn't feel any pressure from water pump? I'm hoping it's
water pump issue rather than head gasket (ugh!)
Thanks for the help!!!!!
After the car reaches proper temperture, the hose should be stiff.
It may be a strong possibility that your coolant cap is defective... which
would cause the bubbling noise as in overheating. Cooling system need
pressure to raise the boiling temperature.
Bingo!!!! Cap was defective or maybe a combo of thermostat & cap
issues.. car runs at 100 mark and below.... also a trick for a lazy
electric cooling fans in front- tap it and if you get it spinning,
once at high revs bang it with a rubber mallet, a couple good whacks,
it seems to have cleaned the armature or scuffed up the brushes or
I weaseled my way out of throwing in the towel with this classic MB
that I love... this car is an ultimate driving machine ($54K new back
then, I paid less than 10% of original price and it drives about the
same, maybe smoother)...much different than the later e's... not as
sporty but thoroughbred MB... I owned a 1965 220sb as my first MB that
set my standards for MBs... Early posts of mine about rough running
after 15 minutes warm up may disappear with cooling system fix....
One good lesson through all of this is:
If you can not nail down exact problem, start replacing cheapest item
first within system where problem exists.
This is an order to consider for diagnosis:
Check for white exhaust steam
Check oil color if milky may be internal leak
Check coolant level when hot- be careful of hot/high pressure
Check coolant color- should be clear yellow tanish cast not brown or
redish (transmission leak) or green(wrong coolant), MB coolant is
special mix (or Zerez GO5)
Check for leaks- everywhere
$6 radiator cap---- just replace
$175 ea Electric Fans---B4 you buy- make sure they turn on when hot-
if lazy to start after tapping (see prior message for tip to resurrect
Free Pressure Test--- Autozone test equipment loaner
$40 thermostat----B4 you buy--can remove and try the hot water test to
open/close it (see prior message for tip removing)
$250 Radiator----B4 you buy--try flushing it with hot water and feel
heat transmission to see if clogged or remove and take to radiator
shop to clean/test it ($80)
$375 Water pump---B4 you buy--try all prior steps
$400 Fan & clutch---B4 you buy-see how is spins when hot and cool (may
not operate well is other system problems)
if you have a bad head gasket it might show up during pressure test
(not sure about leak fixes with pour in products.. ugh)
I'm sure there are a couple of other nuggets to check cooling system
but also make sure you have good coolant and proper amount bled
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