FWIW, I've had studs on my 6.9l for about 2 1/2 years and maybe 10K miles, and the only engine problem I'm having is an exhaust leak (and some IP issues)...
Well, that was short lived....(sigh)
- Thread starter zigg
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dsblack
Full Access Member
I had a 6.9 that had some very small cracks in the valve area to the water jacket. This would cause me to loose water when it was heated and cooled, but If I ran it 1000 miles only turning off for fuel, I lost no water.
Never had air bubbles...
this will be a good one to find. interesting......
Never had air bubbles...
this will be a good one to find. interesting......
sle2115
NRA LIFE MEMBER
Not sure of an exact number, but there are quite a few guys that are running the studs with no problems - I don't think studs are the issue.
I still think you might be working out all the air, might have a little spot where air is getting drawn in as well while cooling down. I know it is not real confidence inspiring though.
I still think you might be working out all the air, might have a little spot where air is getting drawn in as well while cooling down. I know it is not real confidence inspiring though.
zigg
Full Access Member
I hear that, but the kicker is, that the pressure in the rad just keeps climbing even after it is hot.
I tested my other truck for comparison this morning. Ran it up to temp, then released the pressure into the overflow, and hooked up the tester. I ran it, and after 10 minutes of idling, the pressure was around 3-4psi. When I released it, there were no bubbles.
On my new engine, did the same. Ran it up to temp, then released the pressure into the overflow. Took about 1 minute to release the pressure with major bubbles and foam. Hooked up the tester, and it was up to 15 psi in 10 minutes, and when I released it, again, there was major foam and bubbling to release the pressure.
This might sound dumb, but if the thermostat wasn't opening, could it just be boiling on one side, and turning the coolant to steam. I don't have a dial gauge, just the dash one, but it is not way up there, just around the "o" in normal, if that means anything...
I'm waiting for a call from Paul at DAS, see if he's got any other ideas.
Zigg
swampdigger
Full Access Member
A blocked inlet to the water pump can cause it to cavitate and froth your coolant too, although I'd think it would raise the temperature of your motor accordingly. But a hotspot could definitely create bubbles, but still have the remainder of the coolant the proper temperature.
And with with the RTV on the front cover/waterpump, a nice chunk of that floating around could be causing a headache.
And with with the RTV on the front cover/waterpump, a nice chunk of that floating around could be causing a headache.
Compu Doc
Full Access Member
When ever I put a thermostat in a car or ruck I would always test it first to see if i opened correctly in a pan of water on the stove with a thermometer. I'd rather have one not opening at that time before it is installed.
On the Cadillac ambulance it would run all day and not show any signs of overheating if I was not on the highway. If I went on the highway it still would not show any overheating signs until I shut it down then you could hear the coolant boiling. Replaced that thermomstat because upon testing it it would only open partially.
On the Cadillac ambulance it would run all day and not show any signs of overheating if I was not on the highway. If I went on the highway it still would not show any overheating signs until I shut it down then you could hear the coolant boiling. Replaced that thermomstat because upon testing it it would only open partially.
zigg
Full Access Member
Well, I think I solved it.
I ran the truck just till the gauge was showing on the dash, and the idle had dropped down.
I then pulled into my driveway so the back of the block was higher than the front.
I pulled the belt off the water pump(I've converted this engine to serp belt)
I then pulled the plug where the 6.9 glowplug controller goes, and put in a fitting like the one to send coolant to the heater core, and put a 1/2" clear plastic tube on it that reached up higher than the rad. The temp of the coolant was warm, but not hot to the touch.
Started the truck up, and with the rad cap off, the coolant rose up in the tube to match the top of the rad. Topped off the rad, and watched.
Within 10-15 seconds, great big burps of air were coming up out of the tube from the driver's side head.
So, I guess I'll be pulling the head(s).
We'll see what this turns up.
Zigg 
I ran the truck just till the gauge was showing on the dash, and the idle had dropped down.
I then pulled into my driveway so the back of the block was higher than the front.
I pulled the belt off the water pump(I've converted this engine to serp belt)
I then pulled the plug where the 6.9 glowplug controller goes, and put in a fitting like the one to send coolant to the heater core, and put a 1/2" clear plastic tube on it that reached up higher than the rad. The temp of the coolant was warm, but not hot to the touch.
Started the truck up, and with the rad cap off, the coolant rose up in the tube to match the top of the rad. Topped off the rad, and watched.
Within 10-15 seconds, great big burps of air were coming up out of the tube from the driver's side head.
So, I guess I'll be pulling the head(s).
We'll see what this turns up.
Zigg
f-two-fiddy
Registered User
I allways burp my 6.9 from the head plugs and the heater hose. The 2 highest points.
Try that before you tear into it.
FWIW, most burping procedures I've ever seen require a HIGH idle for 20 mins, or longer on some engines.
From what I remember, you've been working on this for a long time. The Heater Core was prolly bone dry? You might just have massive amouts of air traveling thru the coolant system.
If the coolant was entering a cylinder, you would have hydrolocked it during the pressure tests?
It sounds like you have one of those pressure release type radiator caps? Try a NEW solid cap?
You've converted to Serpentine. Make SURE the water pump is turning the right direction.
It might be worth pulling the valve covers, and inspecting the studs. Just to confirm that none of them have cracked the bottom of the holes into a water jacket?
Try that before you tear into it.
FWIW, most burping procedures I've ever seen require a HIGH idle for 20 mins, or longer on some engines.
From what I remember, you've been working on this for a long time. The Heater Core was prolly bone dry? You might just have massive amouts of air traveling thru the coolant system.
If the coolant was entering a cylinder, you would have hydrolocked it during the pressure tests?
It sounds like you have one of those pressure release type radiator caps? Try a NEW solid cap?
You've converted to Serpentine. Make SURE the water pump is turning the right direction.
It might be worth pulling the valve covers, and inspecting the studs. Just to confirm that none of them have cracked the bottom of the holes into a water jacket?
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Mont91
Full Access Member
A head , or block, can be cracked just enough to let the high pressure combustion gasses through but not water back through. The 6.2 bus I drive would not circulate at an idle through the heaters and would blow the cooling system empty when pulling hard. Shop checked for combustion gases and found none. drove it this way for 2 years. 4 days after the shop checked it water started coming out the tail pipe. Both heads cracked at both ends.
icanfixall
Official GMM hand model
Zigg... Find a shop that can pull a vacuum on the cooling system. Its been talked about here and is the best way to fill an empty cooling system like in these trucks. If you can find a small refrigertator compressor you can make it a vacuum pump. I use these to pull vacuum on my ac system and it works fine. About 27 inches of vacuum. All you need to do is soldier on the fittings needed and make up a cap for your radiator. I sure hate to see you pull it down only to find nothing wrong. Then put it back together and have the same thing happen again. If you want to use my hydro plates just let me know.
zigg
Full Access Member
I hear all this info. It's all good stuff. I've checked every suggestion you guys have thrown at me.
But, as I mentioned before, the real issue is not the air. If air was trapped all over the place, the burping bubbles out over time would make sense, but what doesn't make any sense is that the pressure in the rad just keeps climbing. To me, the bubbling in the overflow is a symptom, but the real problem is increasing pressure in the system.
On my other truck, the pressure never gets over 4psi when it's hot.
On this one, it just keeps climbing up and up and up.
No amount of air bubbles in the heads or rad or anywhere could account for the pressure to keep climbing.
The only thing that I can think of that can account for the pressure to keep climbing up once the engine is up to temp, is combustion gasses somehow getting into the coolant...
Zigg
But, as I mentioned before, the real issue is not the air. If air was trapped all over the place, the burping bubbles out over time would make sense, but what doesn't make any sense is that the pressure in the rad just keeps climbing. To me, the bubbling in the overflow is a symptom, but the real problem is increasing pressure in the system.
On my other truck, the pressure never gets over 4psi when it's hot.
On this one, it just keeps climbing up and up and up.
No amount of air bubbles in the heads or rad or anywhere could account for the pressure to keep climbing.
The only thing that I can think of that can account for the pressure to keep climbing up once the engine is up to temp, is combustion gasses somehow getting into the coolant...
Zigg
icanfixall
Official GMM hand model
Zigg... You are probably correct. Most here just hate seeing you get back into it but things have to be down for a good reason. It may be very hard to find why its leaking. On my original motor I was using 6 gallons of water in 32 miles round trip to work and back. I really felt it was cavitation but when I tore it down and pressure checked the block to 30 lbs I didn't find any leakers. I know that cylinder was rusty and really looked for something but found nothing. The best I can figure out is the new (8 year old) head gasket let go but not that you could "see" it. My other head gasket (OEM with 374,000 miles on it) worked fine. Go figure. When you pull it down I sure hope something stands out for you. It'll make you sleep better.
f-two-fiddy
Registered User
Have you even let it get hot enough to open the thermostat? It sounds like a "short jaunt" is all she's seen. Your going to have more pressure with the thermo closed.
Both of my rigs build pressure while at normal operating temps. The rad hoses are hard. It's normal.
4 PSI is not
Have you confirmed H2O Pump Rotation? New Cap?
It might be worth putting some die into it, running it a bit, and checking the oil to see if it's migrating.
I've changed radiators on both of my trucks. It seems to take quite a while to get the air purged. On the 85, I added the final quart to the expansion tank about a week after the job was complete. Haven't had to add more in over a year.
Both of my rigs build pressure while at normal operating temps. The rad hoses are hard. It's normal.
4 PSI is not
Have you confirmed H2O Pump Rotation? New Cap?
It might be worth putting some die into it, running it a bit, and checking the oil to see if it's migrating.
I've changed radiators on both of my trucks. It seems to take quite a while to get the air purged. On the 85, I added the final quart to the expansion tank about a week after the job was complete. Haven't had to add more in over a year.
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zigg
Full Access Member
Well, I haven't started to tear into it just yet. I'm going to give it one more run just to be sure.
I have taken it on several runs that were more than just a "jaunt" I've had in the back of my mind the "Ford" break in procedure, and I've been trying to accomplish that. It involves driving the rig gently to a place where you can get it going to 30mph and then tromp it and accelerate to 50mph full throttle, and then decelerate to 30 about 10 times... So, the area I've chosen is about 2 miles from my home, and you'd think by the time I drove over there, and ran it back and forth, and then drove home again, it'd be up to temp for sure. The dash gauge(I know, I know,) reads at the "O" in normal.
Oil is clear. Used 2 different caps, one a 7psi, the other a 13psi release type. They both seem to work correctly. When the rad is cool, I fill it up, and the overflow to the "low" line. Run the truck, and it pushes coolant out into the overflow, it goes up about 2 inches(twice as much as my '86) and then bubbles constantly. When I leave it to cool, it pulls coolant back in, but the rad retains air at the top, and the overflow goes down, but still about 1" above the low line. If I siphon the excess out of the overflow, and put it back into the rad, it just tops it off exactly, so it looks like there's no coolant actually missing, and the oil is spotlessly clean.
I'm going to try the clear hose on the passenger head and see if there's any bubbles coming from that side, that should confirm it...
The pump appears to be rotating the right direction, but, I can't actually see any flow visually through the top of the rad with the cap off, even when it's down a bit. I seem to recall that usually, when it's up to temp, you can see a bit of flow splashing and swirling in the rad?!
I'll confirm this this morning when I take it for a final run.
Zigg
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