| Author |
Message |
Chris 85 RTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 15, 2006 - 3:47 pm: | |
I have read some of the archived and current threads on this issue, and there seems to be a wealth of information, but of course not exactly the information I am seeking, so I hope you will indulge my asking further questions on this issue. First some background then the question.
On longer runs at contast high speeds (> 55 mph) my RTS with 6V92TA and V731 slowly starts to overheat. I backoff to 55 before I get into the red. In discussions on the RTS board it has been suggested that the trans might be dragging 2nd gear and I had a few questions about that.
1) Is this a known issue with these model transmissions? It has been suggested that this is because of the city gearing of the RTS, but also suggested that this is the result of a worn vavle body. My trans seems to shift fine otherwise.
2) Is there anyway to prove this is the problem, before guessing and paying for work that I don't need? Measure the fluid temp into the heat exchanger, or measuring the pressure via a test port under operation, etc??
I've read the threads here on the air cooler idea, and that seems to me to be the way to go, add a cooler before the engine cooler.
Thanks in advance for any further info. |
Chris 85 RTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 15, 2006 - 3:48 pm: | |
Any update from Brian Brown on his cooling issues? |
David Hartley (Drdave)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 15, 2006 - 4:12 pm: | |
These are only some ideas,
My RTS did a similar thing, turned out that the difference in driving in city traffic in a stop and go and up to 45 to 50 the cooling system was pretty well balanced to get rid of the extra heat.
At 65 mph I used to get what was explained to me as heat saturation which with the fan turning faster and the engine putting out more heat combined with the water/oil transmission cooler
building up extra heat that what was happening was that the air was blowing past the air intake louvers on the side of the bus so fast that a negative pressure air was being created which reduced the cooling ability of the system. I had actually caused that by putting one of those fancy debris brush across the rear bumper and it interfered with air flow. (vapor lock)
Sorry about that long way around...
A couple of things to check are; Fan Shroud and any rubber seals around it. The radiator should have a rubber shield from it to the side panel to keep recycled hot air from getting sucked back into the radiator.
The next thing to check is that the large rubber air-dam that hangs down across the front of the engine cradle is still there and not damaged. Loss of that huge mud flap will cause overheating because it is needed to help create the vacuum in the engine compartment so the fan can pull air through at road speeds.
Just trying to help.... |
Chris 85 RTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 15, 2006 - 4:46 pm: | |
Thanks David, I am really trying to find a methodical way to approach this problem, so I am not just throwing money at various parts, so I appreciate the additional info on the simple things to check. Thanks. |
Greg Peterson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 15, 2006 - 9:28 pm: | |
The V731 is a computer-controlled transmission. I do not have one but I do have an Allison 1000. I can connect it to the Allison Pc based test program and find out all the present and previous fault codes that have occurred during operation. I bought the manual and it shows many pages of fault conditions that the computer can measure and store.
You can connect the computer and drive the vehicle and it will show everything that is working properly or failing.
If the V731 works the same way you could go to an Allison distributor and they could connect you up and exactly diagnose the problem. Again I have no personal experience with the V731 but I retrofitted the Allison 1000 into an application and this diagnostic tool was very helpful in making it work. The Allison distributor was nice in not charging me for the hookup but I did buy the Allison TCU from them for $1500.
The entire question you have on temperature and gears etc. are easily diagnosed with this tool on the 1000. Maybe some one else knows if the V731 works the same way.
One other suggestion, make sure your temperature gauge is working properly. I just had an issue with the temperature gauge and idiot light on the vehicle with the Allison 1000 and new Cummins ISB. The old gauge was showing that the engine was hot and after awhile the idiot light came on. I was almost convinced to start tearing into the thermostat when I realized that the check engine computer light did not come on. I plugged the engine computer into my PC and used a free Cummins program from the net. It did not show any fault codes or abnormal engine conditions. After the typical amount of wrestling I found out that I had a bad sender and a bad gauge that had just the correct flaws to cause the idiot light to also come on. I replaced it with a new gauge that was identical and it all works well. I should have got a CAN bus temp gauge but they are rather pricey and I would have to run the CAN bus up to the front of the vehicle.
Computers can be a big help sometimes. Again I do not know if the V731 has the same capability but if it does it could really help.
Good luck and enjoy the hobby |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 16, 2006 - 4:53 am: | |
If youre not at screaming rpm (2000 + at cruise) you could simply try what GM did on the early Coaches.
Install a full width mud flap IN FRONT of the drive package.
The full width skirt lowers the pressure in the engine spaces , making the existing cooling more efficent.
Half a dozen mud flaps , or an old industrial belt should do it.
FAST FRED |
Pete/RTS Daytona (Pete_rtsdaytona)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 16, 2006 - 8:24 am: | |
FF
That is a standard part on every RTS i've ever looked at - they WILL overheat without the front engine "mud Flap"
Pete |
Chris 85 RTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 16, 2006 - 8:40 am: | |
FF, why do you mention 2000+ at cruise? I top out at 63 mph, which I assume is 2100 rpm against the govener? The heat does not drop but does not climb if I back off to 55ish, which I am guessing would be about 1800 rpm.
I do have the full width mud flap, though it may be torn as I recall. |
Phil Smith (Phil_smith)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 16, 2006 - 1:53 pm: | |
Hey Pete
How bad do you think the flap could be torn or worn down before it makes a difference in the performance? Mine is 75% or so and torn in places.
Phil in Az |
Pete/RTSDaytona
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 16, 2006 - 5:38 pm: | |
Phil
don't have any idea how much of a missing flap will hurt ya ??? |
Bill Gerrie (Bill_gerrie)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 16, 2006 - 10:46 pm: | |
Many years ago I talked to GM re overheat problems and they said the mud flap all the way across had to be there and also the pans under the engine account for 20% of the cooling. The V730 or V731 can be checked very easily with 300 psi gauges connected to the ports in the valve body. Their location is shown in the service manual. I have the gauges mounted in the dash so I can see if anything like you mentioned happens. Never had a problem with the clutch packs coming on together in the V730 or V731 but did in a VS2-6 many years ago. Bill |
Brian Brown (Blue_velvet)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 16, 2006 - 11:17 pm: | |
Hey Chris, here I am. Yes, I have read about the "clutch dragging issue" on V730s. But it is seldom a real issue... so, it's just not very likely to be the cause of your overheating. You can do a stall test per the manual to make sure it stalls at the proper RPM. But I suspect that it's something else.
From what I've read, a stock V730/V731 setup can overheat at prolonged highway speeds, esp. if the trans. cooling system is not at 100%. The transits never were intended to run all day at hwy. speeds, so it wasn't likely on the engineers' minds.
Using the engine cooling system to also cool the tranny might be part of the problem. Hayden and other industrial manuf. make air-to-oil coolers that some folks use on their V730s to offload some of that heat.
So, if you've checked the rest of your cooling system, you might consider adding a supplimental air-to-oil cooler and find some place to mount it which will receive plenty of fresh air. It certainly couldn't hurt.
Some background for those that haven't read my V730 posts...
My V730 has ONLY an air-to-oil cooler on it. My 4108 had the automatic put in sometime during its career and they installed the stock trans. oil to engine coolant cooler then. When the engine was rebuilt, they discovered some pinhole leaks in the unit and replaced it with the air-to-tranny oil cooler. The previous owner found that this setup kept the engine temps. cooler AND the tranny temps. cooler.
On my first long trip with the bus, I started having those tranny overheating issues. I discovered that the fan on the cooling unit was turning the wrong way and overloaded the fuse. I've since fixed that issue and also added some venting in the side of my coach: http://www.brownland.org/bus/4108/trannycool/
The update:
The tranny now runs at 180 degrees on the flats and the fan seldom has to come on (it's on an alarmastat relay). The free air I've given it must help quite a bit, as does the fan turning the right way. The tranny oil does heat up good (up to 230deg.) on a long climb, but I think that's normal when pulling a grade unlocked.
HTH,
Brian Brown
Longmont, CO
4108-216 |
Donn Reeves
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 17, 2006 - 8:40 am: | |
Cris,
My RTS's water temp runs at 182 and the trans at 200, no matter what I do to it,how fast I go or how much rpm it turns.However the hottest day I've run it so far is only 95 degrees.All these bandaid solutions are fine,but they don't address the problem.I know it's frustrating tring to find the cause of the excess heat, or lack of cooling,but you really need to find the problem,not cover it up.You need to check radiator efficiency,Themostats,waterpump,sealing around the radiator and fan shroud, fan belt and accuracy of the gauge.A lot of this can be accomplished easily with a heat gun.You already know that you have to block up the engine doors on the passenger side, because this will destroy the vacume created by the mud flap.My engine was a smog engine bfore I rebuilt it,and it had 200 degree themostats in it,plus advanced timing,small ports and higher compression.All those things could add up to running hot at high RPM.Your trans could be the culprit,but I would check all the basics before I spent money in that direction. Good luck, Donn RTS NJ |
Chris 85 RTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 19, 2006 - 1:44 pm: | |
Thanks for all the inputs.
200 degree thermostats, never heard of that, interesting. |