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Topic: 91 U300 Bulkhead and AC Questions (Read 3023 times) previous topic - next topic - Topic derived from Coach Build Numbers

Re: 91 U300 Bulkhead and AC Questions

Reply #50 –
My 1991 U300 with 3:07 gears won't go into 2nd gear above about 35-40 mph, which is good because it would be over 2000 rpm if it did. I've been trained to never rely on safety devices to save equipment from destruction, so I always think about how high the rpm will be before I downshift. If in doubt just don't do it. Brakes are a lot cheaper than an engine overhaul.

As for the engine running cooler at higher rpm, I did a lot of experimenting in Aridzona this summer with temperatures up to 119 degrees and I wasn't able to make the engine any cooler by raising the rpm. I suspect the air is just too hot and no more heat transfer can take place no matter how much more air the fan blows through the radiator. Also consider how thick the radiator is and how hot the air is by the time it reaches the back row of tubes... but fear not for all these things make your radiator an excellent candidate for a surprisingly effective and very affordable radiator sprayer... more about this after I fully test the one I fabricated this summer in extremely hot AZ... (pant, pant)

Your fuel efficiency matches what mine was before I started towing a motorcycle trailer. Recent events lead me to believe my fuel injector(s) may have contributed to a noticeable loss of fuel efficiency. I'll replace them soon and try again.

If you need an 8D battery be sure to check Parts Plus. I've bought three of them and they always have the best price by far. The batteries appear to be very high quality according to my experience with them to this point. The oldest ones I have are two years old currently with no problems yet. The most recent one I bought was earlier this year and it was $145.82 ...which is about $1 per pound! haha... I considered AGM batteries but the cost is so far out of line that I can't justify it. I can replace my batteries several times and still come out ahead. I've read a report from a battery manufacturer that makes both AGM and flooded cell batteries that AGM batteries actually have reduced performance compared to flooded cells in most situations and that RV manufacturers only use them in the newer coaches because they don't require monthly water checks... but I can check a lot of water for those prices... so when a bunch of people on this forum who spent waaay too much on their batteries disagree with me, go ahead and do a few minutes of research on Google to see what the battery manufacturer(s) says. Also consider that all batteries in size 8D are "deep cycle" and there's no point in paying extra, just buy an inexpensive ordinary cranking 8D at Parts Plus and you've got the best RV battery that smart money can buy. I did quite a bit of research to verify this a couple of years ago, but don't believe me cuz you can easily prove it to yourself with Google... Just for the record I installed my first AGM battery in my motorcycle a few days ago, but it cost the same as a flooded cell and I don't have to constantly check the water in the tiny battery anymore so in that case it was worthwhile.
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: 91 U300 Bulkhead and AC Questions

Reply #51 –
@Dennis Don't misconstrue what I'm saying about engine rpm. A lead foot is not the proper driving method for hills. In the hills you want to keep a close eye on the engine temp gauge. What I should have said is that rpms don't kill 6v92's overheating does! Since yours is the 300hp (I'm assuming this since it's a 91' don't think FOT bumped the hp to 350 until 92') overheating may not be as big an issue but you still want to stay on top of it. Generally foot to the floor generates the maximum amount of heat. It's better to have the throttle about a inch or so from the floor. If the engine is lugging with the throttle there or even to the floor it's time to slow down and downshift. You mentioned cresting the hill at 42 mph. I don't think you can go into 2nd at that speed. One of the coolest things about the Allison is it won't let you do really stupid stuff. Say requesting 2nd gear at 42 mph. It will eventually honor your request for 2nd but only after your speed has dropped low enough that you won't over-rev the engine. If I need 2nd I'll request it then slowly let up on the throttle until the coach has slowed enough that the Allison will allow it. After the shift is complete I floor it to keep as much momentum as I can. All with an eye on the temp gauge. :)

If while climbing your engine temps start rising that's a clue you need to downshift. It all depends on what the road ahead looks like. If you are in sight of the summit and your temps are below 200º you are probably ok to continue but if no summit in sight and you are approaching 200º downshift and ease off the throttle until it downshifts. Do this as often as required even if it means 10 mph in first gear. Just pull into the slow lane and put your flashers on. No embarrassment in that. The embarrassment is when you're the guy at the side of the road with an overheated or blown engine!

Sorry don't mean to lecture but this is important stuff! :)

On to happier subjects since you are in Oregon if you travel a few of the back highways look for a closed weigh station. Usually if you just pull in the scales are still operational and they have an led display on a post in front of you. Just pull up slowly until you see your weight on the display. Write it down then pull up and weigh your rear axle. If you want to get crazy circle around and just put your passenger wheel on the scale and subtract it from the total weight to get your individual wheel weights. Gotta love Oregon. No sales tax & free weigh stations!

see ya
ken
The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: 91 U300 Bulkhead and AC Questions

Reply #52 –
Some one mentioned to me about detroits using misters on the radiators?
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: 91 U300 Bulkhead and AC Questions

Reply #53 –
Used them for years on 8v71's.  Depending on ambient temps, but  a 5-10 sec. burst, will drop cooling water temps 10 degrees.  Generally only need it when climbing. Do not think I used more than 10 gallons any given day.
Problem is, you generally have to remove nozzles and soak in ospho, every month or so, to keep clean.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: 91 U300 Bulkhead and AC Questions

Reply #54 –
@Bob Several of us have added misters to our radiators. I've been planning a write up for some time but life keeps getting in the way. :( I'll just tease you a with a picture.

see ya
ken

The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: 91 U300 Bulkhead and AC Questions

Reply #55 –
On the subject of radiators, an often overlooked maintenance is to backwash the radiator to keep it clean for good airflow. I have an outside hot water faucet and every fall before winter storage I spray hot water from the outside in. My son watches inside to guide me and keep from spraying too much on the engine. The fan stops most of the spray.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: 91 U300 Bulkhead and AC Questions

Reply #56 –
Quote from: prfleming –
...an often overlooked maintenance is to backwash the radiator...I spray hot water from the outside in.
Since the cooling fans "suck", I would think "backwash" would mean to spray from inside (the engine compartment) out?
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: 91 U300 Bulkhead and AC Questions

Reply #57 –
Right, depends on the coach year I think, on the coaches with rear radiator, the airflow is out the back. Key is to wash opposite the airflow...Also, I'm thinking the side radiator coaches don't accumulate as much road dust.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: 91 U300 Bulkhead and AC Questions

Reply #58 –
Quote from: Chuck & Jeannie –
Since the cooling fans "suck", I would think "backwash" would mean to spray from inside (the engine compartment) out?

Good in theory,

But, the "cooling package" is made up of multiple layers, which make washing from BOTH sides the practical way to do it.  At a minimum, you have the CAC (Charge Air Cooler) and radiator.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: 91 U300 Bulkhead and AC Questions

Reply #59 –
@Jim,
Quote
Problem is, you generally have to remove nozzles and soak in ospho, every month or so, to keep clean.
That's why I used cheap 1/4" tubing and drilled 1/16" holes instead of nozzles. It would cost me all of 1 or 2 bucks to replace all the hose you see in the picture. So far works great. Just have it hooked into the pressure side of the fresh water pump with a 12v 1/4" N/C solenoid controlled by a dash switch.

Here is the one I used. This example is a Normally Open you need a Normally Closed for this project. Couldn't find a N/C on ebay at the moment that looked like the one I installed. There are plenty of N/C solenoids but they are a different design. They should work just as well. I liked this one because it has push in connectors and I didn't have to buy extra fittings.

1 4" 12VDC Electric Solenoid Valve Push in Connectors Normally Open 12 Volt...

see ya
ken
The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: 91 U300 Bulkhead and AC Questions

Reply #60 –
On these mister setups, do you use distilled water to minimize mineral buildup on the cooling fins?
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: 91 U300 Bulkhead and AC Questions

Reply #61 –
Quote from: Chuck & Jeannie –
On these mister setups, do you use distilled water to minimize mineral buildup on the cooling fins?
I guess you could, means separate tank and pump. Do not think any more buildup than rain or running on wet roads.
I use the misting nozzles [home depot, ebay etc.] because they produce a very fine mist in a wide pattern that evaporates immediately when the mist hits the radiator. I have tried pvc pipe with tiny hole drilled it, but found a lot of the water just ran down the fins and to the ground. This caused me to use a lot of water. The water from the misters is  fully evaporated on the radiator fins, which leads me to think, the best heat transfer rate for the gallon.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: 91 U300 Bulkhead and AC Questions

Reply #62 –
I considered using misters for my radiator sprayer but the radiator is so thick and hot that hardly any water makes it out the back of the coach in liquid form, almost all of it evaporates. I drilled holes in plastic tubing with the tiniest drill bit I have and it works way better than I expected. I need some of the holes to plug up with calcite because I got a little carried away and drilled a few too many holes. I pumped over 25 gallons of water through the radiator sprayer in half a day of driving through the Rockies and over the continental divide with my foot to the floor all the way up and a big smile on my face... especially after suffering all summer without the sprayer to that point.
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: 91 U300 Bulkhead and AC Questions

Reply #63 –
Quote from: RRadio –
I need some of the holes to plug up with calcite because I got a little carried away and drilled a few too many holes.

Try toothpicks; if you are really frugal, used toothpicks probably work.

Trent

Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: 91 U300 Bulkhead and AC Questions

Reply #64 –
...you know me too well!  :))
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: 91 U300 Bulkhead and AC Questions

Reply #65 –
On the long pull out of Farewell Bend on I-84 headed east when I topped out at 42 mph at the top of the grade, my engine temp stayed at 180, outside temp was about 70-75 that evening, and the trans temp was also down where it is most of the time.
I too have read a lot about keeping the radiator clean, especially with a DD which sometimes tends to leak/spit oil which collects dust as it 'sprays' thru the radiator ::) so I have sprayed water thru the radiator and washed quit a bit of crud out of it.
Anyway, overall I think the DD handles the road, heat, long grades, etc rather well. I mentioned that I was rather impressed with the mileage on the first outing of 9.6 mpg climbing a lot of grades with a headwind.
Lately, I have been helping the widow of a friend of mine who passed away a couple of years ago sell off some of their vehicles, antique tractors, trailers, hot rods, etc. They were well known car collectors in the PNW, and had a large collection of street rods, and antique cars. Recently she decided to sell their 2000 Vogue Featherlite luxury 45 ft coach, powered by a 500hp 3406 Cat with the 6-spd Allison. This is a big coach with a large slide, tag axle, and much heavier then my U300 I'm sure. It's along the lines of such coaches as the Newell, Prevost, Blue Bird, etc. I have been cleaning it up, sorting things out, etc and noticed today that it has some sort of engine info reader on the dash, so I took a picture of it that shows the lifetime overall fuel mileage thus far at about 24K original miles. Now, my friend would often tow a 24 ft car hauling trailer behind it with some type of car he bought at an auction or one he was taking to a show so I am sure that helped to lower the overall average. And owning many large over-the-road trucks and heavy equipment, he liked to move right along! And it does have the power, even for such a big coach, to get right up and move along! 8) But then it should, having about 200 hp more then my DD. But I will always pass that Vogue at the pumps!
However, right about now I am feeling pretty smug about my better fuel mileage ;D, pretty smug indeed!
NE Oregon and SW Idaho
1991 Grand Villa Unihome U300 40ft #3807
6V92 and an Allison auto

Re: 91 U300 Bulkhead and AC Questions

Reply #66 –
...wait until you compare your fuel efficiency to a pickup truck pulling a big fifth wheel ...and be sure to ask them what their maximum range is between fillups right after they tell you their fuel mileage :)
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)