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1999 ford ranger 3.0 done a coolant Reservoir bubbling ?

(1999 Ford Ranger)
in Monroe, NC on April 25, 2018
I recently done a coolant flush on my 1999 ford ranger 3.0 jut emptied and replaced and left the cap off and ran the engine a little to remove any bubbles in there, well today I noticed that the coolant reservoir tank bubbles slowly during idle and bubbles when truck is turned off then stops... any ideas what this could be? Would it possibly be air in the system? If so what’s the best way to release it? I’m hoping it isn’t a head gasket but there is no white smoke from the exhaust and I only filled the radiator up about half a cup since coolant flush.. also the coolant reservoir was filled to the cold line, let the truck run for ten mins today and it raised about half an inch higher..

Coolant gauge stays middle to low, seems to run fine.. no visible smoke from muffler or leakage from pipes other than condensation on start up
What seems to make the problem better or worse? Idk
How long have you had this problem? Just noticed it yesterday and today but unsure how long it’s been bubbling
Tags: coolant system, ford, ranger
Displaying 1 answer & 9 comments
Popular Answer
on April 25, 2018
Re-check coolant level in the *radiator* after overnight park - before starting engine.
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on April 25, 2018
Will do tmo and get back, as I just took it out for a drive tonight, also is the coolant gauge normally go up to the middle stay there for maybe 30seconds then go back down? It is never steady but it never gets hot neither always middle or cold even if I’ve been driving for 30mins / 40miles even it’s always like this
on April 25, 2018

IF coolant level is ok - may need new radiator cap .. Failing cap will result in excessive coolant ‘bypass’ ~ flowing into the recovery tank .. (Bubbling).
on April 26, 2018
Checked the coolant on the radiator and it is fine today, and the truck is on a hill so will need to level it out, and the coolant reservoir is back to the cold fill line, I’m gonna throw on a new temp gauge sensor and a radiator cap today and leave the rad cap off and make sure there is no bubbles in the system.. everyone’s been telling me I’ve a head gasket that’s bad but there is no signs of smoke or anything! I’ll get back with results
on April 26, 2018

Combustion leak test will determine if head gasket is blown - or not.
on April 26, 2018
Put a new radiator cap on and it isn’t bubbling no more? Also let the truck heat up a good 15mins with the cap off with slight revs once I’d rev it the coolant level would go down then once I let of it was spilling out slowly.. normal? Then the thermostat kicked on and it drank coolant so I topped it off and then threw the cap back on..
on April 26, 2018

Many times it is difficult to purge ‘ALL’ air from cooling systems after repairs have been made - checking coolant after extended park and before engine is started is the most accurate way to check ‘radiator’ coolant level - just monitor engine temperature gauge for awhile - you should be good to go.
on April 26, 2018
Awesome, one last thing, temp gauge obviously doesn’t rest at the C line it goes below it when the truck is cold, once running it’ll move up to just below the middle mark and stay there then when I drive it’ll go down to the C line and then back up to middle very slowly every so often.. normal? I just replaced the temp gauge sensor.. still does it but just slower.. I thought it should be a steady middle mark
on April 26, 2018

Replace thermostat!

Then purge air from system again.
on April 29, 2018
Turns out it was just the temp gauge sender unit, replaced it and the temp gauge stays at a steady middle!!
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