A cooling Tale

[LutherC]

I have had a cooling problem for the last eight years I have owned my Bus and have tried different solutions. Here are the latest. First the data: 1977 MCI-8, 8v92T engine, 754 tranny with a 333 differential.
I replaced all the rubber gaskets on the Radiator doors and sealed every opening that would allow air to bypass the radiator. I cleaned the cooling system using 7 quarts of Zerk Radiator cleaner, label recommends driving vehicle 3-6 hours, my Bus was blocked up, so I ran the engine on high Idle for 4 hours. When I drained the cleaner I didn't see any crud come out. The local charter Bus operator told me about a product from Pro Blend out of North Carolina that is supposed to lower the temperature 28 degrees. yes I know what your thinking, another Snake oil salesman. I am also very skeptical of all these type products, but the charter operator convinced me it was worth a try. So I put in 14 gallons and filled the rest of the system with distilled water.
I also talked to Pedco in Calif. about my overheating problem (they changed out a 8v71 to the 8v92). I explained that I keep the RPMs up(1900 to 2000) when running hot to get maximum air flow. He said that is a mistake, high rpms equal more fuel, higher horsepower and more heat. His recommendation is to keep the RPMs between 1600 and 1650 which is the optimum point of the torque curve and with my injectors 375 HP.
Previously when the outside temperature was 95 degrees + I couldn't go 55 MPH without the engine temp going over 200 degrees.
So last week I drove from North Alabama to Michigan and back (1300 miles). I left at noon and the outside temp. was 100 degrees. I ran at 1650 RPM, which equals about 63 MPH and the engine temp stayed between 180 and 184 degrees. However, I did not have any real steep grades to go up. But there were a few long grades in Kentucky on I 71 that caused the temp. to rise to 190. I am still not convinced the overheating is solved but this is certainly a big improvement.
Thursday we are leaving for a trip to California and will travel over 5,000 miles round trip. That will be the ultimate test. I will post the results when I return.
Luther
     

[luvrbus]

Luther,if you are coming on I40 through Needles its hot about 110 degrees email me if you need a place to park for a night have 30 amp service

[JackConrad]

Luther,
   Glad to hear your bus is running cooler. Taking Jasmine home with the bus gave you a nice "test" run.  Good luck and have a safe trip.  We have shown our place twice since we have been home. The first couple (the ones that emailed us while we were at your place) really like our place but she would have a 55 mile trip each way to work.  The other couple that looked at our place on Monday showed up in a 45' MH. They seem interested, but no offers yet.  Jack

[edroelle]

Unless Pedco changed the radiators,  you have radiators that are too small for the 8V92 in hills and mountains.   If you are not satisfied with the compromises that you go through, consider installing '102 radiators - Gumpy's sight has the part number.   Price about $2000 from Diesel Radiator.

Also,  I think you may have the smaller fans.  I kicked-around in a bus company's yard and compared sizes a couple of years ago.  Measure the fan diameter and width.  MCI opened the fan outlet considerably in later models with 8V92s.

With those changes, you would help your situation considerably.  MCIs are still not engineered like an automobile where you do not have to observe the temp.

Ed Roelle
Flint, MI

[JackConrad]

Looking at Luther's bus, not sure about radiator size, but he does have the larger fans.    Jack

[rdbishop]

Luther,

Check your muffler and see if the inlet and outlet are the same size (about 6"). I had your problem for years till someone asked me if I had changed my muffler with the engine change. I was told at the time by charter bus mech. that it did not need to be changed. I put the turbo muffler for a MC-9 and I can run the speed limits.

Luck to you,

Richard

[Chris 85 RTS]

I'm not clear as to what was "fixed".  If you drove slower, keeping the RPMs down, you used less horsepower, thus generated less heat, thus ran cooler.  Nothing was "fixed".  My bus slowly overheats also, unless I slow down, then it is okay.  However, that did not fix anything.

[LutherC]

My Bus has the larger Radiators (sheet metal was modified to make them fit), small pulley and large squirrel gage blowers. The inlet to the muffler is 5" to 6", I need to check it to be exact.  At this point I don't know if the problem is "fixed" but the situation has certainly improved. Previously I wouldn't have been able to run at even 55 MPH on a 100 degree day without the temp going over 210. So I think the improvement is due to a combination of factors. And after all the end result is what matters to me. The true test will be my trip out west.

[LutherC]

Trip update:

The trip to Carlsbad Caverns, Grand Canyon and Los Angeles was without a problem. The Coach ran OK but grades of any significance were a challenge. First, climbing at 1650 RPM helped to keep the temp below 210 degrees. However, when crossing Hoover Dam it was 105 degrees and when going up the steep grades toward Vegas the temp. started going over 210 and the black smoke was bellowing out of the exhaust. So I found a spot half way up to Bolder City and pulled over to cool down. In addition, I was creeping along at 15-20 MPH at times. The trip from Vegas to L.A. across the desert; the outside temp was 100 degrees and the engine temp stayed below 200 degrees (of course going DOWN Baker grade was a breeze).

While in L.A. I went by Pedco's Diesel shop. I had broken an exhaust manifold stud while attempting to replace the gaskets and it was next to the OTR A/C compressor and required removing the head to remove it. While it was torn apart I had them check the Turbo Charger, because before I left home I removed the blanket insulation from the exhaust system and found the clamp between the exhaust turbo and the compressor was very loose. When disassembled we found the vanes on the compressor were worn and just by eye balling it, there was 1/8"+ clearence between the end of the vanes and the housing. The mechanic who rebuilds the turbos said it should be .040. So I had them install a rebuilt Turbo.

Next, we tackled the Jakes. They have never worked very well.  The right bank had been adjusted a couple years ago by another Mechanic at Pedco. He set them with a screw driver until the engine changed sound and then backed off 1'2 turn. After this adjustment the Jakes worked somewhat better. The left bank wasn't adjusted at that time because of the work involved to remove the exhaust blankets, exhaust pipes and Air cleaner. Before I left home I removed both valve covers and checked the Jake settings with the intention of setting up the left bank to the same clearance as the right bank. I found the left bank set at .059 but the right bank was at .016. Spec. is .059. So I knew this wasn't correct and decided to wait until I went to Pedco. At Pedco they checked the solenoids and all four were working and the clearance was reset to .059. I test drove it and the Jakes still didn't work properly. So they pulled it apart again and we engine with the valve covers off. The Solenoids were all working but the master and the slave valves on each side in the back were not actuating. So only half the valves were being held open. Both solenoids were removed and we replaced the o rings. The right side now worked but not the left side. We then replaced the left back solenoid and now all eight valves worked.  Ah, a moment of enlightenment, just because the solenoids work doesn't mean everything is OK.

After discussing power vs. temp. with Virgel Cooly the owner, I decided to change the injectors from 7A75's to 9A85's or 375 HP to 408 HP with a minimal decrease in fuel economy.

Wow what a difference in performance on the drive from L.A. to San Diego. Much more power, no black smoke and temp. still at 180 degrees. Jakes stop working as well as they had in L.A. ( I will consult with Jacobs when I get back home). I am now anxious for the real test, the drive back to Alabama. We will leave Calif. Friday and go to Clarkdale Arizona to visit friends and then start toward Alabama. I will up date this thread with the results when I get home.
Luther

[JackConrad]

Luther,
  Glad to hear Pedco got most of your problems taken care of. I am curious what is going on with the Jakes.  Enjoy the rest of your trip and give me a call or drop me an email when you get home.  Jack

[DrivingMissLazy]

I also started with my Jakes adjusted to .059 cold and they seemed to work great, expecially before the engine got up to operating temperature when they only operated half @$$'ed.
I went back in and re-adjusted them to .055 cold, and man oh man what a difference. I then had great Jakes andy time, all the time. I drove well over 100,000 miles like this so I am certain it did no harm to the valves.

[TomC]

.055 is what Don Fairchild used (as did the old crew from Delaney and Ahlf in Bakersfield) and with my car in tow will slow the bus enough where I have to switch from one head to two heads coming down the I-5 on the Grapevine going north. When I had my truck with the 8V-92TA, I could go down the same hill with 80,000lbs with very little braking-good thing since I was going over the Grapevine every day for three years-either north or south 6 days a week-even so my brakes lasted over 300,000 miles.  Good Luck, TomC

[LutherC]

Well we arrived home in Alabama on Saturday from Calif. We logged close to 6,000 miles on this trip without any problems. But my Webasto stopped working on two occasions. I disassembled the unit and cleaned the photo cell and fire chamber. But I subsequently realized that both times my fuel was down to 1/4 tank. So I suspect the level was below the pick up tube. With a lot of fuel, no more problems.

The engine performed flawlessly with the new injectors and turbo. Plenty of power and no black smoke. The temperature usually was between 180 and 190 degrees. While traveling up I 17 from Phoenix to I 40 at Flagstaff (an elevation increase of about 4,000' ) the temperature went up just over 200 degrees on the long grades but if I set the RPM's to 1650 the temp dropped back to 195. And I was still able to maintain 40 to 45 MPH. This is approximately twice as fast as I could go before the engine repairs. Some of the really long steep grades slowed me down to 25 MPH but I was chugging along in the truck lane with emergency flashers on and 6 big trucks in front me so I wasn't embarrassed. And by staying at 1650 RPM the temp remained at 195.

What a joy to drive by occasionally looking at the speedometer and not constantly watching the temp. gauge.  As we passed through New Mexico the outside temperature was 85 - 90 degrees and a few times I came off the porch and ran with the big dogs at 80 MPH. The temp went to about 205, but what a ride!!!!

Now I need to find the time to pull the valve covers and check the operation of the Jake brakes.

One final note, while in California I stopped by ABC bus to pick up an oil pressure gauge. The one in my engine compartment gave it up. I met Neil Wells their western regional parts manager. We were talking Bus parts that were still available for MCI 8's and he mentioned that he has a warehouse full of SS side panels that he would like to get rid of and at a very very good price. His contact info: 877-222-2878, 714-758-1041, nwells@abc-companies.com

Luther

[JohnEd]

Luther,

If you increased the injector size and upped the HP you are now generating MORE heat than you were before PEDCO....right?  If you improved the performance of your turbo you have more air in the engine and the reduced black smoke means you are again making more power...right?  The only thing you did to reduce the temp was to adjust your speed to 1650rpm,,,,correct?  I think you are way ahead of where you were before PEDCO as I don't think you were making the spec  HP and heat associated with it when you got there.  No wonder you are so tickled with a supposed 30hp gain.  I don't think it should hsave been all that apparent a improvement if you were making what you thought.

I don't agree that a higher rpm means more HP and more heat.  HP and heat are a function of the fuel burned and the HP you are making.  High rpm and easy on the gas is less HP than a lower rpm and floored.  Remember that post about high rpm creating more bubbles in your coolant due to pressure drops in the system?  It sounds to me like you are loseing cooling capability when you push the coolant around faster.  In the old days you could open the cap to retard a leak so you could make it home as the reduced pressure would leak slower.  I tried that with a modern engine and it spewed the coolant out in a minute.  It was boiling somewhere in that system and the gauge never got over normal till it went empty.  The new stuff needs that cooling sys to be under pressure to not boil even at the normal temp. so it must be flashing to a higher tem in spots and I suspect that one of the spots is the head.   I read in recent post that bubbles reduced your cooling capacity by 40%.  What is the highest pressure cap you can run?  Can you get ahold of one of those testers that check pressure pop-off? 

I sure hope you resolve this.  I think you could get off the porch any time you like and stay awhile if you care to.  You should be there with the 102 radiators...others are and they are majking more power than you.

Wasn't there a change to the 8V92 in 86(?) that affected/improved cooling?  Or was that just durability?

Good luck and keep us posted.  5 years is a long time to fight a problem.  You have to win!!!!

John