7.3 IDI with Allison 1000 overheating

[AzironaZack]

Also, I still have the 5.38 gear set. I may swap that in

If you grab a blade and the fan freely spins with a cold engine, the clutch is no good. Its overlooked because it spins with the engine whether its freewheeling or being driven to spin.

The fan clutch drags pretty heavily when I rotate the fan with the engine cold. I'll test it properly while hot sometime soon and report back.

On a 100• day uphill you should hear it cycle on and off, similar to a semi-truck. You know that fan sound you hear as they drive by and it kicks on?

Most of the times you get enough airflow on flat ground that the fan freewheels. If you're not getting a noticeable fan roar when the coolant gets hot the clutch has failed.

I'll keep my ears on next time and see. It's super loud in the driver's seat all the time, so it could be coming on/off and I just am unaware.

I did the A-2000 5spd swap with a 5.9/4.11s/11R22.5s. 5th is .74? and your sixth is .64? so you might have seen 6th with the 5.38's but will not have the power to push that tall of an OD without massive power upgrades. The high-dollar motor coaches you see flying by are pushing 500-600hp. https://www.rvtechlibrary.com/engine/Cat_RV_Performance.pdf

Yeah, I don't see sixth very often with my 4.44 rear. A long downhill on the interstate I'll get there, but otherwise 5th seems to be the highest gear the bus will still push.

I am very seriously considering swapping my 5.38 gears back in. I'm hoping there's a cheap 5.38 differential available locally that I can slap in and drive around for a bit to see how big a difference it makes. It will mean going back through the tuning process for the trans, but so be it.

My 5.9 has timing, better turbo, governor spring and needs an injector upgrade to get the egt's down. It keeps up with semi's except long uphill pulls - egt's, but have seen 88mph on level/downhill, so your swap as it is will go faster than you'd probably care to.

Right now I can hit 70 pretty decently. It's pretty hard to push this brick through the air at that speed, but the bus will do it. It's super nice to be able to more appropriately keep up with traffic. I still don't keep up with semis, though. I'm jealous!

In the meantime, though, it'd be nice to drive up the mountain without the coolant temperature warning coming on.

 

[La Camioneta]

Also, I still have the 5.38 gear set. I may swap that in

The fan clutch drags pretty heavily when I rotate the fan with the engine cold. I'll test it properly while hot sometime soon and report back.



I'll keep my ears on next time and see. It's super loud in the driver's seat all the time, so it could be coming on/off and I just am unaware.

Yeah, I don't see sixth very often with my 4.44 rear. A long downhill on the interstate I'll get there, but otherwise 5th seems to be the highest gear the bus will still push.

I am very seriously considering swapping my 5.38 gears back in. I'm hoping there's a cheap 5.38 differential available locally that I can slap in and drive around for a bit to see how big a difference it makes. It will mean going back through the tuning process for the trans, but so be it.


Right now I can hit 70 pretty decently. It's pretty hard to push this brick through the air at that speed, but the bus will do it. It's super nice to be able to more appropriately keep up with traffic. I still don't keep up with semis, though. I'm jealous!

In the meantime, though, it'd be nice to drive up the mountain without the coolant temperature warning coming on.

While I do wonder about your intercooler affecting airflow, some deficiency in fan, water pump, or thermostat seems more likely. With my B-700, I assume the radiator/intercooler are oversized as the 5.9 was the smallest engine offered in the 700 series.

You could probably look up your chassis parts numbers for radiator/intercooler with the 466T and see if the radiator was the same for all engines. If not, the 466 radiator may be a better fit, as your 444 probably makes as much heat being intercooled and turned-up as the T466.

As far as changing gears back and forth, this helps Spicer Transmission Ratio RPM Calculator

 

[BamaBus]

While I do wonder about your intercooler affecting airflow, some deficiency in fan, water pump, or thermostat seems more likely. With my B-700, I assume the radiator/intercooler are oversized as the 5.9 was the smallest engine offered in the 700 series.

As far as changing gears back and forth, this helps Spicer Transmission Ratio RPM Calculator

I was kinda waiting for someone to mention the intercooler. I was wondering if that was affecting the heat and air flow since it was an aftermarket add-on. Maybe just enough to affect the temps by a few degrees. (edited)
Also I wonder if adding a trans cooler before the rad would lower the coolant temps a few degrees since the sump temp was in the 210° range
Thirdly, what about a Horton fan clutch with a different fan? Costly(for me), but would increase air flow and would provide a means of manual activation.
And for the rearend, Cadillackid had a thread where he calculated the revolutions to make adjustments to his Allison 1000 programming.
An amateurs observation

 

[La Camioneta]

If I remember the lore correctly the trans you have now makes much less heat because of the lockup function. The pic is of my radiator/intercooler, intercooler seems similar in size to yours, and is faired smooth to the radiator to prevent air leaking around.l

Assuming trans temp is a function of water temp, we're back to a deficiency in the cooling system.

 

[La Camioneta]

Thirdly, what about a Horton fan clutch with a different fan? Costly(for me), but would increase air flow and would provide a means of manual activation.
This is a trap I fall into when something in a system is on its way out.....

While the IDI engine is known for its simplicity and longevity, it is prone to cavitation. Using coolant additives can help prevent this

Are you running an anti-cavitation additive?

 

[AzironaZack]

I was kinda waiting for someone to mention the intercooler. I was wondering if that was affecting the heat and air flow since it was an aftermarket add-on. Maybe just enough to affect the temps by a few degrees. (edited)
Also I wonder if adding a trans cooler before the rad would lower the coolant temps a few degrees since the sump temp was in the 210° range
Thirdly, what about a Horton fan clutch with a different fan? Costly(for me), but would increase air flow and would

There's lots of changes to this bus. It's a skoolie, after all!

I'd like to stick with the mechanical viscous clutch. It's practically new and was quite spendy (like 500 bucks). I'll follow Borg-Warner's diagnostic procedures this weekend and see if it checks out.

If I remember the lore correctly the trans you have now makes much less heat because of the lockup function. The pic is of my radiator/intercooler, intercooler seems similar in size to yours, and is faired smooth to the radiator to prevent air leaking around.l

Assuming trans temp is a function of water temp, we're back to a deficiency in the cooling system.

Yeah, I've got doubts about it being the transmission causing the overheat. An auxiliary trans cooler would probably be beneficial, in any case. I am 16000 pounds.

Thirdly, what about a Horton fan clutch with a different fan? Costly(for me), but would increase air flow and would provide a means of manual activation.
This is a trap I fall into when something in a system is on its way out.....

While the IDI engine is known for its simplicity and longevity, it is prone to cavitation. Using coolant additives can help prevent this

Are you running an anti-cavitation additive?

I am running an additive but I haven't tested the level in a while. Test strips are on the way. Thanks for the reminder!

 

[AzironaZack]

Reporting back.

I had to replace my air compressor pump, which required draining the coolant system, so I took the opportunity to check my SCA levels and add a proper coolant temperature gauge.

SCA level was 0. As in none remaining. YIKES! I added the additive to the coolant before putting it back in. I also swapped out my coolant filter since it's been a year.

The new gauge is by VDO. I put the sensing bulb in the rear-plug position on the driver's side head. I know this is a hot spot for measuring coolant temperature but it's the spot I had available!

I picked up a Derale Hyper-Cool Extreme and will be putting that between the trans and the radiator. The motor will be switched with a Derale thermostatic switch (35022) to turn the fan on at 180 degrees and off at 165. Hopefully this reduces the load on my radiator a good bit.

I'm looking forward to taking it for a test drive up the mountain with the additive and the new aux cooler. I'll update when it happens.

 

[nikitis]

Good Luck! Seems you are going about testing properly.

 

[BamaBus]

What type of coolant do you have and did the coolant filter have SCA added or was it blank?

 

[AzironaZack]

What type of coolant do you have and did the coolant filter have SCA added or was it blank?

The coolant filter is just an inexpensive plain one: WIX 24070.

I really should do a better job watching that SCA level in the future.

 

[s2mikon]

I have installed a bottom temperature gauge in my radiator to assist in managing cooling issues. It looks like you have an extra hole to mount it. I just pulled the radiator drain cock and installed it there. I normally see 20-25 degree spread. Some times the factory gauges go wonky and either break your ride or scare you. I have a F-800 ford diesel I bought at an auction and when I drove it home the gauge pegged about half way home. I shut it down and sent my son to the house to get my IR thermometer. 15 min. later he was back and when I started it back up it was 3/4 to the peg but showing 180 at the top and bottom of the thermostat housing. I installed a VDO in a panel and now I have a good gauge and didn't have a heating issue. But what if it had been the reverse?

 

[AzironaZack]

I have installed a bottom temperature gauge in my radiator to assist in managing cooling issues. It looks like you have an extra hole to mount it. I just pulled the radiator drain cock and installed it there. I normally see 20-25 degree spread. Some times the factory gauges go wonky and either break your ride or scare you. I have a F-800 ford diesel I bought at an auction and when I drove it home the gauge pegged about half way home. I shut it down and sent my son to the house to get my IR thermometer. 15 min. later he was back and when I started it back up it was 3/4 to the peg but showing 180 at the top and bottom of the thermostat housing. I installed a VDO in a panel and now I have a good gauge and didn't have a heating issue. But what if it had been the reverse?

You're absolutely right about the factory gauge. It's this little tiny thing and I don't know how accurate it is, or what the setting is for the alarm going off.

I installed a quality gauge with the bulb plumbed into the driver's side head. It's definitely nice to be able to see the coolant temperature more accurately, even though mine's installed at the hottest point in the coolant loop.

I just drove up my backyard mountain last weekend and kept the IR thermometer in the bus so I could check temperatures if I overheated again. There was no problem with overheating, but that could be because I was driving more sedately, because it was 80 degrees outside (instead of 105), my new rear end gearing allowing me to keep higher RPMs at lower speeds, or probably a combination of all the above.

 

[s2mikon]

Once your t-stat is fully open, your coolant temperature will track with the outside very closely. For example if your coolant is 200 degrees and you have a 180 t-stat and it is 80 degrees outside, if it goes to 105 degrees outside you should see around 225 degrees. You may not see a 1:1 ratio, but it will be close enough to tell you if are good to go.

 

[Booyah45828]

Cool bus. You've done upgrades I was hoping to do to mine before I sold it.

Couple things. IDI's run hot, it's the nature of them having the combustion chamber completely surrounded by the cylinder head. Also, compounding your issue is running a cross flow intercooler with a downflow radiator. Having those two mismatched directions creates turbulence between the two and significantly reduces air flow. With a new radiator I'm with the others and believe you have air flow issues, especially seeing that you were low speed while it happened. New clutches can fail, I didn't want to spend the 500 you did, because it required a new fan that required a new shroud and would have been 1000 bucks plus when it was all said and done.

I found an NOS clutch that worked. No suggestion for you with that, just mentioning it because I've been there. Besides running an heavy duty or severe duty clutch, I'm not familiar with your numbers and finding a paper catalog on these things is almost impossible anymore. If you have the old clutch yet, run a self tapper through it then install it on the bus as a test to see if you can hear the fan engaged then.

You should be able to hear the fan, I know I did.

PS I think the 210 is also low, IIRC mine was 230. That's assuming the gauge and alarm switch is correctly working. Mine ran 200-210 consistently, thermostat opens at 192, so 210 will get hit pretty easily in normal operation. Like mentioned install a gauge in the bottom of the radiator and you'll see if it's doing anything or not. Or watch your oil and trans temps as those will reflect lower tank temps as well. IIRC my at545 would run around 180 or so unless it was 100+ out, then it would creep higher.