Can't get Mustang to quit venting coolant!

[j_mac]

Morris,
Thank you for the suggestion. I was thinking about trying that. See, it seems that when the enging is heating up there is a bubble forming in the top of the engine that is being held back by the thermostat and it is displacing the coolant backwards out the lower radiator hose. Having no where to go, the cap vents the excess pressure and coolant. The new thermostat didn't have a burp hole at all. The old one did have the burp hole with the little plastic bead/float in it. I should have checked it to see if it was plugged up. I think I'll go right now and drill that hole and see what happens. Anything to rule out disassembling this horrible engine design.
Thanks again.

 

[j_mac]

Ok Morris,
I took out the thermostat and drilled a small burp hole in it. Refilled the sysem and took it for a drive. The heater still warms up just as fast as before, so the bypass hole I drilled is a non-issue. I didn't have any of the symptoms as I did before. But the reservoir is low on coolant. I'll top it off (after the heat cycle) in the morning and them I'll be able to see if its still building pressure.

This may have worked. I'll keep you posted.

 

[j_mac]

Filled it to the "add coolant" level and took it for a long drive. Its acting normal now. Checked the level after the drive and it is down a little. Will add more tomorrow and see what it does. Trying to level off the coolant level.
We'll see if this is just a Band-aid for a serious problem or if it fixed an air-lock issue.

 

[AdRock]

Even though the 4.6's don't usually have head gasket problems there is an issue with them because of the way they have the coolant flow set up. On the drivers side head the rear cylinder (#8) can get very hot. The coolant flows from the front of the head to the back and then back to the front. So that cylinder tends to run a little hotter than the rest of them. The DOHC 4.6's have the same issue. So you might pull that plug out and see if it looks like it's been burning coolant. You can alleviate the issue with a mod to the intake though.

 

[funnylarri]

j_mac: It's been a while since the last post and I now have this exact issue with my 1997 Crown Vic. I have a 1 year old Radiator and Water pump. I had a little oil (I think)in the coolant when this first started happening a few weeks ago which makes me think my issue is a head gasket. I replaced the Thermostat recently and that helped only slightly. I was wondering if what you did fixed the overflowing coolant problem or if it came back later? Also, if it did come back did you manage to fix it with something else? Thanks!