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Bleeding coolant system/ Coolant filling

3K views 6 replies 5 participants last post by  faadave 
#1 ·
Hello forum, before anyone suggests it, I assure you I have spent almost all day searching this sight and others for the answer before posting.

so here is the short of it.

1996 Mustang 3.8L manual transmission.

I replaced the radiator and water pump then put everything back together.
afterwards, I followed the coolant fill and bleed instructions that I found on here.

Removed radiator cap, removed bleeder bolt on top of the motor, filled radiator to capacity, filled bleeder bolt hole, replaced bleeder bolt, ran the engine for about 20 minutes or so to reach temp, shut it off and let it cool.

The expansion tank has been filled to the area between both the cold/full and hot/full area.

My specific question is based on this:When I remove the radiator cap, I'm seeing room enough for a few ounces of coolant. So I fill it. I've been able to fill the small void with coolant over and over again. There aren't any leaks that I can find and I've vigorously searched everywhere. How will I know when it's taken in as much coolant as possible?

I also noticed that coolant only travels from the radiator to the expansion tank when it's hot and I begin to remove the radiator cap. The pressure being released is allowing coolant to travel through the hose to the expansion tank.

I know air bubbles are a known problem with these 3.8L engines, I just would like some experienced insight as to how to make sure I have enough coolant in my system, and no air.

Thanks for any replies.
 
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#2 ·
Welcome!

Different engines can have slightly different fill procedures (us 5.0 guys don't get a nifty bleeder bolt), but it's not unusual to have to drive it a little to work out a final air bubble. It should no longer need topping off after a drive cycle or two.

If the coolant level is still dropping, there could be an internal leak (like a head gasket) drinking it. The radiator cap might not even be bad if the pressure is being relieved elsewhere. Have you been keeping track of how much you've put in? The system only holds about 3 gallons or so.
 
#7 ·
All of my V6 mustangs never stay "topped off". there is always that little bit of space. I can top it off, then like you say, it goes down slightly. Even between oil changes, my cars never go below that little bit of space. It must just be the design, overflow capture, etc. Now, after driving for a while, or between oil changes you end up putting in a half gallon or something, but see no leaks, then start looking at an internal leak like a head gasket - I've been there too. :wink:
 
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