420SEL coolant not flowing thru radiator

[luvdiesel]

I drained the coolant this weekend to change and refilled. The temperature guage now climbs into the red and I can hear gurgling noises like boiling after I pull back into my driveway and turn off the car. I live in the country and discovered by accident that pushing the throttle down all the way and accelerate hard for a few seconds, the temperature comes down very quickly but then starts climbing back up again.

My thought was that air is trapped and is preventing coolant from flowing thru the radiator. The bottom of the radiator says cool. I tried blowing into the overflow in an attempt to force water thru the system to force out any trapped air. This did not work but intrestingly when I do this I can hear bubbling coming from inside the passenger compartment, i'm assuming the heater core. That indicates that their must be some air space in the heater core that probably shouldn't be there.

Recommendations would be greatly appreciated

[Larry Delor]

With the engine cold, take off the cap, start the car, and re-fill as needed as it goes to operating temp. (turn on the heater too, while you are at it)

Is there any fluid in the reservoir? Once the engine cools down, it should suck up whatever it needs within the engine. Are you sure that your cap is good? Make sure the gasket is good, and that the seating surface doesn't have crud on it.

[JD Tetterton]

Going with what Larry said, but I would also park the car with the front as high as you can ( on a hill perhaps) this will help get the air out of the system. I had the same problem last week.

[david s poole]

that car has a balance tube from the top of radiator to the expansion tank.it sounds to me as though the tubes have shrunk in the radiator and it needs replacing.

[luvdiesel]

Thanks Larry, JD and David.

As per Larry and JD, I drove the car up ramps when cold and let it come up to temp with the resivour cap removed. Some air bubbles did seem to come out. I replaced the resivour cap and drove it. Still heating up.

High rpm's are what bring the temperature down. You could drive all day long in 2nd.

Blowing into the resivour as I mentioned before is strange compared to other cars. On most cars the system will pressurize and you won't be able to blow any more air in. On this car when you blow in you hear a bubbling noise that seems to be coming from under the winshield washer res. I have an 88' 560SEL parts car that I tried this with and same thing. The air that you blow in some how passes thru the coolant and then is allowed to vent.

David, I'm not sure what you meant about the tubes shrinking. Do you mean the tubes internal to the radiator?

I'm thinking about changing the thremostat.

[david s poole]

i read your post more carefully where you say that the bottom of the radiator is cool .CHANGE THE THERMOSTAT.

[luvdiesel]

Ok, I got it figured out. I took the top piece off, the one that has the hose connections, thinking that was where the thermostat was. Wow, all kinds of junk in there blocking passage down and thru the thermostat. I took the thermostat out and flushed everything out good and put it back together. Will refill tomorrow after silicon dries.

As to the bubbling I was getting while blowing into the resivour tank, the air was escaping out of the small nipple at the top of the fill neck. I removed that hose and blocked it with my finger and no bubbling and system pressurized.

Thanks for helping me out with this.

[dpetryk]

Be aware that the cooling tubes in the radiator are very narrow and will clog up. I have had several radiators where half of them were not flowing. Engine temp was fine at freeway speeds but when it slowed down the temp started to rise. You should have heat across the entire surface of the radiator. If part of it is cool that indicates that there is no flow in that part of the radiator. Replace it.