Please Help! Cooling system problem
 

First let me start off with saying hey my name is Preston. Some history on the truck 1987 F350 6.9l idi (I think) with estimate of 120,000 miles. I inherited the truck and my uncle who left me the truck never said how many times the odometer rolled over. The truck shows 20,000 miles now. The reason I say (I think) is because it has all the 7.3idi glow plug system, and belt system, but has the 6.9l 4 speed, and water separator, with factory paint color on the engine.
The problem is that it is blowing bubbles into the overflow tank.
I have searched all the posts and forums for answers to my problem but can’t come up with a solution. What I have done so far. The front water pump seal went out on the truck on a 150 mile commute with about 60 miles left to go. I had to keep stopping and fill the radiator with water and coolant to make it home. The truck never overheated (to my knowledge) or made any bad noises. It was running great and idling fine when I got home just leaking coolant. I replace the water pump and thermostat with factory ford parts. I cleaned the thermostat housing and check ball when replacing the thermostat. I pretested the thermostat and it functioned properly. I did put the thermostat in properly made sure of that. Once re-assembled I tested the check ball and it free moving (I can hear it clinking when I squeeze the upper radiator hose). For the water pump I did see some deterioration on the engine front cover plate behind the water pump impeller, but sanded it up and it got it pretty smooth. I installed the water pump and applied thread sealant to all the bolts (just as a precaution). The truck previously had green coolant, but I changed it to the Fleet charge pink with the SCA pre-added. I drained the entire cooling system (including block plugs), heater core, overflow hose, overflow tank, and flushed with distilled water. I put 5 gallons of coolant and the rest distilled water in it. The inside of the radiator does appear to have some scale in it. I plan to install a coolant filter once I get this problem is resolved. The truck cranks and idles great without any leaks.
The problem is that the truck is blowing bubbles into the overflow as it heats up and is warm. With the radiator cap off and the engine warm it is steaming out the radiator cap opening. I have a temp gun and the block, radiator, thermostat housing don’t get above 200 when sitting idling or driving. I have replaced the cap with a 13 psi cap. The exhaust does not smoke or smell sweet. The engine oil is not milky, and doesn’t appear to be eating coolant. It is however blowing what appears to be steam or smoke out the dipstick and oil filler cap. I think the CDR needs cleaning or replacing. I don’t see any condensation on the dipstick or under the oil filler cap. I did the combustion gas test with the coolant about 2” low in the radiator, and it did not change color, it will blow bubbles in to the cylinder with the blue fluid in it without pumping the primer bulb. I took the fluid around to the exhaust to make sure the fluid wasn’t bad and it turned color instantly. I pressure tested the coolant system cold and it will hold 16psi for as long as you want it to, I even tried turning the engine over (without it cranking) to see if one of the cylinder might have a hole in it but the gauge stays at 16pis no matter what. I just don’t know what else to do. I’m getting so frustrated and can’t figure this out. Any help would be greatly appreciated.

Wow, that hurt my head to read.

To get better response please try to seperate your thoughts and try using paragraphs.

SO you are considered about:

Bubbles coming in the cooling system and steam at the cap
Condensation or "smoke" coming from the dipstick tube when removed while warm?


Some steam or "smoke" is normal from the dipstick tube, its moisture that is leaving the crankcase in the form of vapor. A little is normal, a lot is another issue.


How long ago did you flush the coolant system?

Our cooling systems are huge! 8 gallons is a lot of fluid, plenty of chance for some air to still be in there.

Being that you said you pressure tested it, checked for exhasut contaminants, and the rest of the normal stuff, and it checked ok, I would say the cooling system is probably ok.

I'm going to lean towards just a bit of air still in there. When the coolant gets hot, it expands. This will push up on the radiator cap and open the passage to the overflow tank. It should be pushing air into the oveflow which will be the bubbles you see. Once the coolant cools, it contracts. It will then pull coolant from the oveflow to displace the area the air (bubbles) was previously occupying.

Also any mositure that is on the radiator (anywhere, fins, top, cap, etc) will evaporate in the form of steam once the engine is hot. I thought I had a cap issue after I had replaced my thermostat because there was steam coming from it. After a bit of running (in a 66 degree shop too btw) it stopped.

First time posting, sorry for the messy layout on the post. Thanks for the help.

I flushed the cooling system when I did the water pump and thermostat about 2 weeks ago. I have only put about 15 miles on the truck since.

It could be air in the system but you can see the coolant circulating in the radiator, and the heater is working great. I just got the truck up to operating temp and installed the pressure gauge on the radiator and pumped it to 13psi after idling for 20 min the gauge worked its way up 15 psi before I took it off. I didn't want to over pressurize the system. Any thoughts?

I still think its working ok.

When you open the cap does it make a "psshhh" sound like its releasing pressure or vacuum?

If it is that could mean you're letting air back in there which is then being pushed back out into the overflow via normal operation.

I do not know for sure if it will work itself to where coolant is the whole way to the fill neck on the radiator, someone else will hopefully chime in.

Since its not overheating, youre not losing coolant, most of the system has been service and sounds serviceable, and the heat is functioning I'm going to guess everything is ok.


On my v6 f150 I had a heck of a time getting all the air out and I would get bubbles in the resevoir as you state. I know its a different set up entirely, but it ended up just being a little bit of air that needed worked out.

Also, my apologies if I came off sounding like an arse, that was not my intention. It's very hard to read and think about a subject when it is in a giant blob

At least on my truck, the top of the upper radiator hose is actually higher than the fill cap, so it can(and does) accumulate air bubbles in there.
I would suggest just locking down the cap and driving it. Give it a few hot/cold cycles, and then check that when hot, the upper radiator hose is pressurized and filled with fluid.
Provided that's true, and it is keeping things cool... ignore anything else.

Also, smoke out the dipstick... sounds like blowby.
Our engines produce quite a bit, especially when they are multiple hundred thousand miles old. Mine produces quite a bit, though it should be sucked into the intake via the CDR valve. I have seen some coming out the oil filler cap, though(if I remove it), at idle.

I appreciate all the help guys. I'm going to try driving it for a couple weeks and keep and eye on everything. I will report back if I end up identifying a problem. Thanks again!

Report back if you don't have a problem too, we like solutions and then we will know for sure your case was normal operation :-X22

What he said, x2 your information was good. you did all the right things, GOOD JOB, like he said the cooling system is huge, and until you run it some it will blow bubbles, get her good and warm find a steep hill park nose up, and rev it some, to maybe get the last of the air out, other than that, enjoy your new ride.:-jammin

Thanks guys, I will report back in a week or so. So far so good today, it ran great.