'Burping' the radiator

N

Nick B

Registered
I checked my coolant level in the overflow tank a couple weeks ago, and since then the temp seems to occasionally get too hot. The needle will climb up about about 2/3 for just a few minutes, then settle back down in the middle. Seems to happen at idle, cruising, on the highway... not really dependant on conditions.
Is it possible I have an air bubble in the system? I'm going to put a 180* T-stat in, how do I make sure I don't have any air in the system when I'm done?

Thanks,
Nick
 
RE: 'Burping' the radiator

Make sure you fill the system from the opening on the crossover tube. Then leave the cap on the crossover tube open when you start the car, and top off as necessary. When the car starts to warm up, coolant will start to overflow out of the crossover tube, that's when you put the cap back on. that should keep air out of the system.
 
RE: 'Burping' the radiator

[div class="dcquote"][strong]Quote[/strong]
... Is it possible I have an air bubble in the system? I'm going to put a 180* T-stat in, how do I make sure I don't have any air in the system when I'm done?Thanks,Nick
[/div]

It is possible to have air in the system. I don't think the 'stock' T-stat has a 'bleed' hole, therefore you must wait 'till the t-stat opens to 'burp' air completely from the system. Remember the coolant reservoir is essentially an air separator also. There should be no air whatsoever in the engine block, heater, hoses or radiator. It sounds like from your description you may have some trapped air but not too much.

If the replacement t-stat has a bleed hole, it is easy to fill the system with no air entrapment. After the install, with the reservoir cap and fill cap at the crossover off, fill the system at the crossover pipe until the reservoir is at the full cold level.

http://mark8.org/users/driller/pics/coolantfill.jpg

At this time make sure you have no leaks at the t-stat housing and drain cock. Install the cap on the reservoir. Start the engine at run at idle speed with the heat at max. Continue filling system at crossover pipe slowly until full and then replace the fill plug at the crossover pipe(Yes, this will be messy). Run the engine 5 to 10 minutes at idle until the thermostat opens. Run the engine 2000 rpm for 5 minutes, monitoring the temperature. Return to idle and shut down. Allow engine to cool(overnight best). Recheck reservoir with cold engine and fill to full cold mark.
 
RE: 'Burping' the radiator

When my thermostat started failing, my engine would start overheating and then cool back down. After doing this a couple of times, It stuck closed for a good while. It was on a 40 degree day and the engine started overheating. I got an audible alarm. After stopping for it to cool down a few times, I was close to home and it opened up again. I replaced the thermostat before driving it again. My son's 95 Mustang had the same problem at about the same mileage (75k). Only with the v6 engine, the head gasket blew. My Mark got hot enough one time that it had started boiling just a little. It survived the experience.
 
RE: 'Burping' the radiator

Shouldn't you turn on the heater too, in case there's air in the heater lines? Don't know, but I've heard it before and thought I'd point it out.
 
RE: 'Burping' the radiator

is it really necessary to run the heater? doesn't coolan flow through the heater core whether the heat is on or not?
 
RE: 'Burping' the radiator

I was just recalling service manual instructions. ::roll::
 
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