Totally Stumped

[JeffMoss1]

Hi guys,

Been a while since I've been around. Posted this problem earlier this year, but didn't get any responses. Figured I'd give it another shot since I'm back under the hood.

I'll try and keep it short:

Bubbles in the coolant overflow reservoir. Put my air compressor to the cylinders at TDC and BDC through the glow plug hole and wasn't able to see any bubbles in the coolant through the radiator cap. Did a compression check and all cylinders were good. Used a combustion gas leak tester on the engine 3 times and got no trace of a color change.

Weirdest part of all of this, drove it for about a year like this with no trouble. Air just keeps coming out and I just keep ignoring it. I don't lose ANY coolant.

Engine hasn't been warming up lately so I just replaced the thermostat and I'm trying to burp the system right now and I'm reliving this air issue and just thought I'd see if any of you brilliant IDI folks have any thoughts.

My personal opinion is this:

There is a leak somewhere in low pressure part of the cooling system that sucks air INTO the cooling system and pushes it out of the radiator cap. When the car is turned off, this particular spot either seals itself back up or maybe isn't actually under the water level so it doesn't let any coolant out onto the floor.

No one I have talked to can explain this scenario to me. Assuming I can get the air burped out of the system again, I plan to just continue driving this thing.

Cheers guys, hope all's well.

Jeff

 

[Dieselcrawler]

while you had the thermostat housing off, id you notice if the bleeder ball was present and not stuck?

 

[Black dawg]

when you aired up the cylinders, how long did you leave them aired up?

 

[JeffMoss1]

Thanks so much for the replies.

When I had the thermostat housing off, I did look at the bleeder ball. I read that in another thread. It took me a little while, but I got that little ball in there free by dripping a little bit of mineral spirits into the port and using my compressed air nozzle to dislodge it. When I put the thing back together it was jumping around pretty good in there with an air burst and it was shiny. I'm confident that it should have been working.

When I aired up the cylinders it was during this past summer. I probably left each cylinder for a few (maybe 5) minutes. You think I didn't leave them long enough? I might buy that, but it doesn't explain my negative results on the combustion gas test.

 

[jaluhn83]

Any overheating?

Is the radiator level full? When everything's working right it should be pretty much overflowing anytime you open the cap. If it's low then it means it's not sucking coolant back from the overflow bottle.

Is the coolant mixture 50/50 or close?

Have you tried pressure testing the cooling system?

If everything's working right and you're not overheating I wouldn't worry too much about it.

I had a somewhat similar problem but in my case I was seeing a consistent low radiator tank level (ie, I'd fill it up and then it'd be low after a few drives) and it would get hot under load. Finally figured out that the little air bleed was stuck (despite being free shortly before) and I was getting an air pocket that was somehow pumping out the radiator every time it would heat up and expand.

Possibly you're getting bubbles of water vapor? Maybe the radiator cap is leaking a little bit and not holding pressure? Water at ~190 should give off some vapor naturally, even with the proper coolant mix and more so if it's low on antifreeze. Same thing as when you're boiling water and you start getting steam before a full boil.

 

[79jasper]

Could someone post a picture of the bleeder ball in place?
And is it really needed?

 

[icanfixall]

Shop air pressure is around 120 lbs. Combustion pressure is well over 500 lbs. Just cranking pressure on my engine is 530 lbs. Have the heads ever been off the engine. If so please post what was done and by whom..

 

[Black dawg]

Thanks so much for the replies.

When I had the thermostat housing off, I did look at the bleeder ball. I read that in another thread. It took me a little while, but I got that little ball in there free by dripping a little bit of mineral spirits into the port and using my compressed air nozzle to dislodge it. When I put the thing back together it was jumping around pretty good in there with an air burst and it was shiny. I'm confident that it should have been working.
When I aired up the cylinders it was during this past summer. I probably left each cylinder for a few (maybe 5) minutes. You think I didn't leave them long enough? I might buy that, but it doesn't explain my negative results on the combustion gas test.

I have seen it take 30 minutes to show results with cylinders aired up.
I have never seen a combustion gas test find a small leak on a diesel.

 

[hesutton]

I had bubbles in my overflow tank on the 6.9 in my crew cab. It would puke coolant out the overflow tank when hauling a load, but not empty. She would run hotter than it should as well.

I tested the crap out of the thing trying to find out if I had a bad head gasket. I did compression testing, it was not definitive. I pressurized the cooling system and let it set over 24 hours...... no leak found. I even used refigerant in the cooling system and used a freon sniffer in the glow plug holes to try and find the problem......... nothing.

Finally broken down and pulled the 6.9. Sure enough, leaking headgasket at the #1 cylinder.

Long story above made short........ Even when you test everything like you should......... you can still miss a bad headgasket or cracked head.

Heath

 

[JeffMoss1]

Sorry for the silence. I updated my email address in my settings and I got booted from the forum, so I couldn't reply. Mike just fixed it for me.

Alright, so basically what you guys are saying is this is a HG or cavitation no matter which way I look at it. What bugs me is that my diligence in trying to affirmatively diagnose this didn't pay off. (sounds like I'm not the only one that's gone through this (hesutton).

Icanfixall - heads have been off the engine. I bought this engine in pieces from 69 oiler (Rob) back in 2006, put it together and have been running it ever since. I've got about 25,000 miles on it. I used ARP head studs and went through the torque sequence. I measured flatness of the surfaces roughly with a feeler gage and a scale and I think it should've been good (long time ago now, so can't quite remember what any of the values were.)

I just did something new last night as I tried to burp the air out of the system (again). I put a t fitting in the high pressure heater core line. Cracked that, cracked my aftermarket temp gauge (back passenger), cracked the return side of the heater core at the water pump, made sure all of those had coolant at them before I sealed them up. THEN, i started it up and cracked that high pressure line at the t again, and I had air shooting out of that fitting like a rocket engine. With your guys posts and the shear volume of air I was getting out of that fitting, I'm convinced, this is combustion gas. What else could it be?

I'm still really pissed that the combustion gas leak tester isn't worth anything.

When I did the compression test (this was over the summer) I had almost exactly the same pressure in every cylinder EXCEPT for number 1, which was off by maybe 30 psi or something around there. I'll have to check my notes. Is that enough to say that's the problem cylinder? If I pull the head off will I be able to easily tell?

 

[Goofyexponent]

What about sompression testing the egnine with shop air with the pistons at bottom dead center? That way, it is WERE cavitation, the air wouldn't have to fight to get past the rings and THEN out of the hole in the liner.

I hope it's not block worm, that it is just something like a bad head gasket.

The only problem with a coolant system trying to "SUCK" air is that it's not a vaccuum system. It's under pressure 90% of the time. If you have coolant in the overflow, as well as coolant in the rad, it should just puch out a little coolant when warm, and pull a little form the bottle as it cools off.

Just a stab in the dark, but is your hose that goes from teh rad filelr neck to the overflow bottle free of obstructions and able to flow properly?

 

[hesutton]

When I did the compression test (this was over the summer) I had almost exactly the same pressure in every cylinder EXCEPT for number 1, which was off by maybe 30 psi or something around there.

That really sounds fimilar. Same on my compression testing. Cylinder #1 was 400. The rest were 430-440 range. I also noticed a little coolant on the glow plug when I took it out to do the compression test. But, like I said, it was puking coolant when hauling and I mistakenly assumed it just settled in the recess for the GP and it ran down onto the plug when I pulled it from the block.


Heath

 

[JeffMoss1]

A friend just asked me if it's possible that cylinder isn't firing and maybe that's why the combustion leak tester is reading negative. I said no way, it would sound really obvious if it had dropped a cylinder...

...now secretly i'm considering whether or not that's a possibility.

It bugs me that the leak tester is coming up negative. there is a huge amount of air coming out of the cooling system.

how can i check to see if a cylinder isn't firing?

 

[Black dawg]

I think you would definetely know if it was missing. I think the diesel just doesnt generate much combustion gas idiling, it is pumping quite a bit of air though. I wonder if you ran an exhaust hose from another car into the intake of the diesel, if it would help the test out.

 

[79jasper]

I wouldn't be so sure about it being that obvious. Get one of them digital infrared thermometers, and use it to spot a cold cylinder.