Overheating w123

[digieditny]

1984 300td euro turbo with manual A/C

Summer is coming so I really would like to get this problem fixed before it gets too hot out.

The fan clutch is good. The Thermostat is good. The temp sender and gauge are also good. When it starts to overheat, I turn up the heater full blast and the temps go back to normal. Not sure if any of these clues help at all. I never let it go above 110c. So I don't know if it levels off.

My A/C works great. Would be nice to be able to use it on long drives.

[dude99]

hmm, well the two things that come to mind are a failing water pump (the fins on the impeller can corrode away) or a plugged radiator. I'd try doing a cooling system flush first.

[charmalu]

Check for debris between the Radiator and the Condensor. make sure the fins are not blocked with debris and straighten out any bent fins.

A few people have installed a larger W126 AC fan.

Charlie

[digieditny]

In the haynes manual, it says to test the water pump:

"With the engine at normal temp, squeeze the upper radiator hose. If the water pump is working properly, a pressure surge will be felt as the hose is released".

It also says to check the weep hole. I'll try both of these tomorrow.

I'll see about the coolant flush

[digieditny]

Charmalu. Can this be done with the radiator still installed?

[bricktron]

Originally Posted by digieditny

"With the engine at normal temp, squeeze the upper radiator hose. If the water pump is working properly, a pressure surge will be felt as the hose is released".

that's the easiest test i've ever heard of! no tools required!

[Delibes]

From cheapest to most expensive...

1. Check for any point where you may have pressure loss (leaking hoses, cracks and take appropriate measures such as re-tightening or JB Weld).
2. Pressure wash your radiator fins and get all the road debris out!
3. Flush your radiator thoroughly with Mercedes' citric flush. Their formula is strong and effective, most radiator flushes seem half-hearted in comparison.
4. Replace your water pump; you can install additional mods like the eight-fin fan, a W140 aux fan or smaller water pump pulley out of a W126.

[digieditny]

Delibes. How firm should the hoses be once the car is at temp? Should I be able to totally squeeze them?

[barry12345]

I might suspect old radiator. Take a temperature reader and scan various areas of the radiator. Looking for any cold areas. Junk accumulate between the condensor and radiator has already been mentioned and is a good thing to check.

[funola]

Originally Posted by digieditny

Delibes. How firm should the hoses be once the car is at temp? Should I be able to totally squeeze them?

hose should be squeezable and not rock hard. If rock hard, it is pressurized by compression gas. not good.

[Diesel911]

If the Euro Model has an Auxiliary Fan the Fan is it supposed to turn on when the AC is on?

With out taking the Thermostat out and immersing (suspend the Thermostat off the bottom of the Pot and away from the sides, a Teaspoon of Salt helps decrease the bubbling) it in hot Water with a Thermometer to monitor the temp how would you know it is opening all the way or not?

You also would not know if the Temp Sensor or Gauge was working properly until you check it with a test Gauge.

If you plan to do a Coolant Flush it is a good idea to have another way to get to work as a few have had the Flush open up holes in the Core/Freez Plugs and even the Heater Core.

[w123fanman]

Originally Posted by digieditny

In the haynes manual, it says to test the water pump:

"With the engine at normal temp, squeeze the upper radiator hose. If the water pump is working properly, a pressure surge will be felt as the hose is released".

It also says to check the weep hole. I'll try both of these tomorrow.

I'll see about the coolant flush

I'm assuming this same test applies to OM602 engines. How long are you supposed to squeeze the hose? I would squeeze it for 2-3 second and feel nothing, so I am assuming my pump might be bad.

[digieditny]

Thanks Funola! How's it going?

Barry. Good idea. Will do that.

Diesel911. Yes the Aux fan does come on when the AC is turned on. The car overheats with or without the Aux fan.

I took out the thermostat completely to see if it'll overheat and it still does. So it's not the thermostat. Anyway I checked the thermostat.

I'm assuming that the temp and gauge are fine since the readings are accurate according to my ir gun.

Yes Ive heard of disasters because of collant flush. Will leave that as very last resort.

w123fanman. I dunno. This is what the haynes manual says for w123 1976-1985.

[funola]

put the Tstat back in asap! I've heard the 617 will overheat w/o a Tstat.

[digieditny]

Finally got out there and squeezed the hose and it was firm but squeezable. Seems fine. So now I suspect the radiator. Anyone know how much it might cost to get the radiator removed and flushed? I don't want to flush the whole system.