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Old 10-29-2019, 09:25 PM   #41
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I had this air compressor scenerio on mine.. my bus didnt have amn air dryer.. the air system froze one very cold night... the air pressure ran off the scale.. gauge was pegged way past its maxx.. I started losingmy heaters.. so i stopped and coolasnt was going everywhere... I fixed the frozen air system with new gauge, governor, and an added a heated air dryer.. i still was losing coolant..



one trait I noted was that the bubbles continued in my coolant after I shut the bus pff with the tanks fully pressurized.. a head gasket will only make bubbles while the engine is running..



compressor solved my issue..
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Old 10-30-2019, 02:47 AM   #42
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Chris,


You have verified that it happens ... but what is the condition? How is the air compressor connected to the cooling system?
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Old 10-31-2019, 11:22 AM   #43
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There is no milky oil, no combustion gases, etc. The mechanic is willing to put it in writing that this solves the issue and has a warranty on the part and labor as well.

He had me there for the diagnostic process, which I didn't entirely follow, but it involved the engine being on for quite a while and the compressor disconnected. There was no pressure in the radiator when the air compressor is off and the tanks are bled.
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Old 10-31-2019, 11:25 AM   #44
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Quote:
one trait I noted was that the bubbles continued in my coolant after I shut the bus pff with the tanks fully pressurized.. a head gasket will only make bubbles while the engine is running..
Yes, the bubbles continue long after the engine is off, like 20+ minutes.
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Old 10-31-2019, 11:56 AM   #45
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The service manual I found for one of my engines in Cummins Quickserve online does mention the following (this is for an ISC, but allegedly ISB and ISC are very similar in this regard):
Quote:
A negative result from the combustion gas leak tester, coupled with a continuous flow of air bubbles from the previous test, indicates the following:
  • Damaged fan, shutter, or heater air control valve
  • Air compressor head or head gasket leakage
Also, it would be pretty easy to bleed down the compressed air system, verify the bubbling stops, and re-charge the compressed air system with shop air. If the bubbling began again it'd be pretty obvious that compressed air is getting into the coolant. Make sure shop air is applied at the right place -- if it were on the wrong side of a check valve the test would not be valid.

The chapter on the compressed air system also specifically mentions the coolant lines and an illustration shows the lines connecting to the head of the compressor.
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Old 10-31-2019, 12:23 PM   #46
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Most all air compressors on big trucks are water cooled, so a compressor head gasket can do the same thing.
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Old 10-31-2019, 12:31 PM   #47
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Guys, certain compressors use the engine cooling system to cool the compressor. Operating the compressor creates heat, they have to be either air cooled or water cooled.

Compressors can lose head gaskets and have their blocks/heads crack just like an engine could, and the results would be the same as if the engine did.

Whatever mechanic suggested the air compressor, be sure to thank him. As you've seen, most wouldn't suspect that originally. And as a side note, those blue dye combustion leak detectors don't work the best on diesel engines. It's because the fluid transforms in the presence of carbon monoxide, which is something that a diesel engine doesn't produce a lot of at idle.
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Old 10-31-2019, 03:31 PM   #48
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I did the combustion test a fourth time after half an hour of intense driving on unpaved mountain roads and it still didn't change color. The new mechanic said that it still could be an engine head, and mentioned the same thing, that the block testers don't work well on diesels. After testing the air compressor, he said that it seems unlikely that this is an engine issue, fortunately.

The part is delayed so the repair isn't happening today. I will ask them to test the pressurization with shop air before replacing the part as an additional check.

The mechanic called today and told me that he had been chatting with the other mechanics about my bus (apparently it is an uncommon problem and thus is interesting to them) and they recommended also replacing a "check valve" which is only $30 or so. Because the repair involves draining the coolant, I may ask them to check out my thermostat as well. I already have the part in my tool box so it can be swapped if there is any chance that it is contributing to this issue or to the fact that the big fan behind the radiator does not come on automatically as often as it should.
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Old 10-31-2019, 03:54 PM   #49
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Quote:
Originally Posted by Ronnie View Post
Most all air compressors on big trucks are water cooled, so a compressor head gasket can do the same thing.

THIS.. all the bendix duak cylinder compressors have coolant lines going through the head of the compressor..



the dead ringer for me was the fact that it was bubbling in the overflow tabk after i shut the engine off until the air pressure dropped down.. and I didnt have to warm the engine up.. just run it long enough for the air to pump up .. i'd hear it hiss out the cap.. open the cap release pressure.. and tighten again and within a minute or so all the hoses were solid stiff .. I knew the engine was still barely warm so the pressure wasnt from a hot engine... when the air tank drains were left open i could run the engine and the cooling system didnt lose any coolant..


-Christopher
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Old 10-31-2019, 04:18 PM   #50
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*sigh* it's almost 2020. aren't we supposed to have magic carpets and teleporters by now?
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Old 10-31-2019, 04:47 PM   #51
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Quote:
Originally Posted by cadillackid View Post
THIS.. all the bendix duak cylinder compressors have coolant lines going through the head of the compressor..



the dead ringer for me was the fact that it was bubbling in the overflow tabk after i shut the engine off until the air pressure dropped down.. and I didnt have to warm the engine up.. just run it long enough for the air to pump up .. i'd hear it hiss out the cap.. open the cap release pressure.. and tighten again and within a minute or so all the hoses were solid stiff .. I knew the engine was still barely warm so the pressure wasnt from a hot engine... when the air tank drains were left open i could run the engine and the cooling system didnt lose any coolant..


-Christopher
How do you open all the air tank drains? I seem to have four of them, with a cable going to one on the front left that I can pull. It has a sticker "Drain Air Tanks Daily" but I'm not sure if that single cable drains all the tanks or just one of them.
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Old 10-31-2019, 05:35 PM   #52
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Do NOT use pour in sealers/liquid glass/devil piss whatever another, that junk will clog up the oil-water cooler and will further ruin your engine. Then IF you want to rebuild it you have all that junk in the cooling system that you will never get cleaned back out. I'm not even sure if hot tanking the engine will remove those pour in miracle fixes, those are NEVER to be used on a diesel.

I hate to tell you what your saying sounds really suspect of a blown head gasket or cracked head/block.....
Not even knowing what a compression test is, I'd advise you to slow down and do some heavy studying about engines in general or find a mechanic, you might wind up wasting alot of money if you aren't careful about what you do next friend.
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Old 11-01-2019, 12:31 AM   #53
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Quote:
Originally Posted by PatrickBaptist View Post
Do NOT use pour in sealers/liquid glass/devil piss whatever another, that junk will clog up the oil-water cooler and will further ruin your engine. Then IF you want to rebuild it you have all that junk in the cooling system that you will never get cleaned back out. I'm not even sure if hot tanking the engine will remove those pour in miracle fixes, those are NEVER to be used on a diesel.

I hate to tell you what your saying sounds really suspect of a blown head gasket or cracked head/block.....
Not even knowing what a compression test is, I'd advise you to slow down and do some heavy studying about engines in general or find a mechanic, you might wind up wasting alot of money if you aren't careful about what you do next friend.
Navistar's factory procedure for leaky 2001-2004 DT's is to put block sealant in the cooling system. That alone was the final straw for me and Navistar products.
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Old 11-03-2019, 01:59 AM   #54
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Originally Posted by OlgaAK View Post
*sigh* it's almost 2020. aren't we supposed to have magic carpets and teleporters by now?
We do but they lack ambience and you can't make land yachts out of them. We haven't heard from you since you were contemplating dening up in AK for the winter. Sounds like you found your way south?
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Old 11-03-2019, 06:54 AM   #55
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Physics

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Originally Posted by o1marc View Post
I fail to see where a loose fitting or not enough pressure cap is going to cause aeration of the water. I doubt the cap is the fix, though I also recommend a high PSI cap.
Boiling point is related to pressure. Higher pressure, higher boiling point.
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