Pardon me for posting here, but this is the closest forum that may have some ideas about a problem with a 6.0L engine in an International 4200 chassis. I have an International 4200 chassis supporting an Endura motorhome. The engine is the 6.0L same as used in the Power Stroke Diesels. I’m having a problem with coolant escaping apparently through the coolant tank pressure cap. In the interest of preventative maintenance, I’ve replaced the plastic coolant tank, all hoses, thermostat and the dealer thought the waterpump was sucking air, and replaced that. I have my doubts about the water pump being a problemand replacing it didn't correct the problem.. Running the engine there is no evidence of exhaust gas coming from the coolant tank with a head gasket leak detector, but the dealer said they detected bubbles in the water before replacing the water pump. ???? There is no detectable coolant loss on level roads, but a loss when climbing grades, with coolant temp remaining under 210 degrees. A blown head gasket seems like an obvious problem, but there are no exhaust gas detected in the coolant tank. Any ideas what else could be causing the problem? Thanks

 

Any evidence of coolant escaping the degas bottle at the cap? Caps are rated to hold 15psi (I think). Not uncommon for the cap to wear out & vent pressure/coolant before then. If cap is good, blowing coolant out of the degas (puking) is an indicator of a bad head gasket.

 

With the motor at operating temp stop and let the pressure slowly out of the degas bottle. Then continue on your way for a little and check to see if pressure has returned to the degas bottle. It shouldn’t. T-ing into one of the small hoses coming from the bottle and adding a gauge would give you the actual numbers you are getting in the system to confirm a leak.

 

I second that ^^^ -- looking at the pressure gauge, you would be looking for a sudden rise in pressure to the 16 psi cap limit -- usually when load is put on the engine -- so all you really need todo is put the tranny in 3rd and mash the throttle -- with good gaskets the pressure would not rise much, if at all -- with a bad gasket the pressure will max out at cap relief

Also keep the coolant level below the low line about one inch -- not sure on the buss, but on the trucks keeping the level topped up will blow coolant

 

Degas bottle testing:



Drive engine to operation temp and release pressure at degas bottle cap. Now drive it WOT. Check coolant pressure under load , you should NOT see this pressure climbing:

 

So I was getting ready to post a similar situation with my truck but decided to read your post first. I'll post mine after this one.

Over the weekend, I was towing a trailer and total weight with truck, trailer, and cargo was 21,000. Anyway, I had just filled up with fuel and 2 miles down the road I noticed a ton of smoke behind my tailgate in between the truck and trailer. It was nighttime so not sure what it was but pulled over. Ended up, I blew the lower radiator hose off so I put it back on and made sure it was super tight as well as the upper hose. To my knowledge, I hadn't had any major coolant issues although I did have to add about a gallon a week after I got the truck. (I've only owned it for about a month and a half now and around 5k to 6k miles later).

Unfortunately, since it was night and there were no places open, I had to resort to using water for the time being and then stopped at a local Walmart at 7am and bought 4 gallons of the "works in all vehicles" concentrated antifreeze. Yeah, I know the "green" antifreeze is not good but it's all I had at the time. Anyway, I pulled the trailer about 300 more miles home and had to add about 4 or 5 more gallons of coolant and water (mixture of each) along the way. Not good obviously so I'm sure there's a head gasket issue along with the already problematic Ford heads and possibly some other things. Hard to tell until I tear it apart.

The next day, I needed to tow a 5th wheel camper that weighed 15,080 pounds. So, I bought more antifreeze and headed 200 miles to get the camper. Pickup was fine without a load and I didn't need to add any coolant along the 200 mile trip. Hooked the camper up and headed down the road. I ended up figuring something out on this part of the trip that I didn't think of earlier. As long as I kept it to 19 pounds of boost or under, I wouldn't have any issues with overheating or coolant loss. However, if I didn't have the truck downshift when climbing hills and I tried to push the truck in the gear it was in and make over 19 pounds of boost, I would start to feel a "shudder" which to me felt similar to a transmission shifting or driving issue. However, I believe this "shudder" is actually the coolant being pushed out of the degas bottle due to issues with the sealing of the heads to the engine (whether it's just the gasket or issues with the heads or a combination of both).

So, I figured out that as long as I kept it at 19 pounds of boost or under, I was okay. If I needed more power, as long as I got it to downshift into the lower gear, it would still make power and not force the turbo to make boost over 19 psi. So, I wouldn't have any coolant loss. At least not nearly as much. I ended up towing the camper back 200 miles without any issues.

Now, a couple things that probably helped my situation.

1. It was relatively cool or cold in my area where I was traveling. According to my external temp button on the automatic HVAC system, it said it was about 46 to 48 degrees outside. I know these things aren't perfect but I'm confident that was close. Plus, based on the weather history from yesterday in the area I was traveling and the time, it said it was between 45 and 50 degrees. So, perhaps the temp is more accurate than I give it credit for.

2. I have a fan switch in my truck so I can force the fan to be on full force while driving which helps as well while towing loads. Although it's loud, it is better than overheating.

3. I didn't have many big hills to climb or when I did have some, they were pretty short by maybe 1/4 mile to 1/2 mile at the most. Nothing major. So, if I wanted to, I could gain speed going down the previous hill or pay attention to when I was coming up on one and get a decent run at the hill without having to lose too much speed by the time I got to the top. In other words, I paid attention to what my boost was and wasn't able to use the cruise and had to actually use my foot (poor me, I know). It worked though.

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Now, I'm not sure if you are encountering the same situation at all but I thought I would throw it out there to see if it was a possibility. For you, maybe you're having issues even at a lower boost level say 15 or even 10 psi. Or, maybe it's at a higher level at 20 or 25 psi or more. I don't know.

I did purchase a brand new degas bottle cap when I got the truck so that shouldn't be any part of the issue but I suppose anything is possible. New parts do fail as well. But, I know I've got other bigger problems going on.

Does your vehicle "shudder" like mine when you get to a certain boost level? Mine shudder or shake isn't really bad at all. It almost feels like you're just driving over some rougher road such as a little rougher asphalt or something similar. But as I mentioned earlier, to me, it feels like it's a transmission "shudder" but I found out that's not it. At least not based on this new info that allowed me to keep it from overheating and spitting out coolant.

I use a Torque Pro app while driving to monitor stuff. I don't know if you have one but if you don't, you should get it. It's free online if you know where to look or you can simply pay $5 in the app store. If you have an Android device, you can get a regular bluetooth adapter online that's about $10 that plugs into your OBD port under the dash. If you have an Apple device such as an Iphone or Ipad, I believe you need an adapter that uses Wi-Fi instead of bluetooth. Make sure to look into this if you're not sure. I was going to use an Ipad one time with the same bluetooth adapter I had been using and it wouldn't work and I think when I did the research, it said that I needed to get the adapter that had Wi-Fi capabilities. It seems weird since there wouldn't be Wi-Fi in your vehicle but perhaps that's the way the communication works between the adapter and the Apple device.

Sorry for the long post. Hope this helped a little.