Engine Fan Speed

Topic: Engine Fan Speed (Read 1347 times) previous topic - next topic

Engine Fan Speed

August 07, 2015, 08:22:11 pm

Our 1995 U295 has an overheating problem that likely may be related to fan speed. We don't seem to have enough air circulation to cool the engine (Cummins C8.3) radiator when driving in high temp weather. Our mechanic unplugged the wiring harness in order force high-speed operation. While the fan speed did increase, it was only a moderate speed increase. The fans certainly do not roar. The suction will not hold a piece of cardboard against the grill. Yes, the radiator has been both blown out and washed.

Has anyone on this board experienced a similar fan speed issue?

Re: Engine Fan Speed

Reply #1 – August 07, 2015, 08:56:22 pm

Have you changed the filters in the hydraulic reservoir? Could be a restriction on the suction side.

Certainly worth a couple of filters and couple of gallons of oil to verify before getting into something really expensive.

Re: Engine Fan Speed

Reply #2 – August 07, 2015, 09:52:50 pm

One of the main reasons paper will not suck on outside grill is all the MANY places where hot air is recirculated is instead of bringing in outside air. EVERY space around the radiator shrouds on the inner side of the fan area must be sealed so ONLY outside air is pulled through inner-cooler & radiator. The factory's 'conveyer-belt' material has lots of spaces for hot air coming from fans is sucked back to the input side of the fans.
We used spray foam to fill all holes, but did have to put a few holes in bottom to let captured water drain down.

Re: Engine Fan Speed

Reply #3 – August 07, 2015, 10:25:46 pm

I thought all the mechanical cummins were wax capsule controlled for fan speed. If that is true, what did he unplug? If not, I'd get a temp gun and see what return temps u are getting from the bottom of the radiator.

Re: Engine Fan Speed

Reply #4 – August 07, 2015, 10:55:53 pm

Thanks, Brett. Next step will be to change filter.

Krush - what should I expect to see for a return temperature when the temperature gauge is reading 225 degrees (for example).

Barry - I don't think we have a shroud issue as the coach never overheated until we had to have a fan motor replaced (purchased from Foretravel) because it was leaking oil. The mechanic verified proper rotation direction.

Re: Engine Fan Speed

Reply #5 – August 07, 2015, 11:01:37 pm

Ours has a custom radiator and there is an enormous gap between the fan shroud and the radiator. We still manage to keep cool except climbing western mountains in 90's weather. Admittedly we do heat pretty quickly in those circumstances and have even had to take action (stop, high idle, disconnect toad) to cool it down.

The foam is a good idea. I'm trying to figure out what I could put there that woudn't get ripped right into the fans and destroy them. I was thinking of getting a couple pieces of L shaped steel and riveting it to the fan shroud. Would take care of most of hte leakage.

I'm not sure how bad the giant gap between the radiator and the charge air cooler is...

Anyway the point is when our fan is on high speed and it is running high idle, it is an enormous flow of air, even with giant leaks. But it's not that fast at low idle.

Re: Engine Fan Speed

Reply #6 – August 07, 2015, 11:39:03 pm

For what it may be worth, I just came Thur the mountains of Wash Idaho and Montana in 95 degree weather, I have installed a misting system on our u300 with a Detroit and everyone knows how sensitive they are to heat. I used it when my temps got to 190 degrees and it worked great I did downshift and kept my RPMs up around 2000 and came through with out any problems. It really as quite easy to do and it sure saved me a bunch of stress.

Re: Engine Fan Speed

Reply #7 – August 08, 2015, 01:12:20 am

OK, Piku brings up a good point that I've been meaning to ask. With the coolant at an elevated temperature, does the engine have to be at high idle for the fans to operate at high speed? Or should the fans still operate at high speed with the engine at low idle?

Re: Engine Fan Speed

Reply #8 – August 08, 2015, 06:11:16 am

Quote from: Andy 2 – August 07, 2015, 11:39:03 pm

For what it may be worth, I just came Thur the mountains of Wash Idaho and Montana in 95 degree weather, I have installed a misting system on our u300 with a Detroit and everyone knows how sensitive they are to heat. I used it when my temps got to 190 degrees and it worked great I did downshift and kept my RPMs up around 2000 and came through with out any problems. It really as quite easy to do and it sure saved me a bunch of stress.

How did you install it and how does it work?

Re: Engine Fan Speed

Reply #9 – August 08, 2015, 08:27:28 am

Whether a coach temp gauge shows overheating or not, all recycled hot air reduces outside air from doing what is needed. Increased cooling is always better. All shroud gaps should be eliminated. This is a simple and effective way to increase cooling system efficiency, which affects engine oil, coolant, hydraulic and transmission. We first learned about the 'gap' problem from a Foretravel engineer 10 years ago, and our spray foam has held up. We did spray black paint over the foam.

Re: Engine Fan Speed

Reply #10 – August 08, 2015, 10:18:58 am

Hi Barry, Well I had talked with Ken Hat about his and followed his lead. I started by routing a 1/4 inch line from my pump bay and tied into the drain side of the fresh water tank with a pexs tee ran the line up over the tanks and came thou where my over flow tube went I will relocate the over flow tube later. I bought a piece of heavy wall PVC for running hot water put a 1/4 inch fitting caped the rear end and drilled 8 1/16 holes in the tube. I then took a 12 volt water pump and and tied it to the supply and tube to the mister. I ran a 12 gauge wire Thur the wiring tunnel to the front of the coach and came up under the couch and placed a switch on the dash. I put a couple of pictures to give you an idea. note that the picture of the valve was my first attempt with a small pump and decided to go with a surflo instead.
In that picture it show that I tied into the house pump at first and I would have had to leave the pump on while underway so I changed it because the small pump I used would let the pressure tank push water past the smaller pump.

Re: Engine Fan Speed

Reply #11 – August 08, 2015, 11:39:37 am

I too thought we were having a problem with fan speed a couple of years ago so I took the coach back to FOT to check fan speed. Others had mentioned that they had a two speed thermostatic switch that kicked the fan into high speed at 195 degrees. We found that our Vintage Coach had a different fan speed controller that was relative to rpm rather than temperature. I requires down shifting to keep rpms up when things get hot. The fan speed was adjusted slightly higher to meet spec but the fact was that I had the coach loaded to the maximum. Coach and towed weight really make a difference in creating cooling system heat.

We have noticed that reducing weight, I no longer carry two of everything, makes climbing hills a lot less of a chore. However some planning is still required. We have been playing the high heat, steep road game the last two weeks in Colorado. Last week we went over Le Veta Pass at 89 degrees. It is 5 miles of 6% grade and 4 miles of 3% going west. We weren't smart enough to take off the towed and had to pullover three times to cool down even with the Desert Cooler, a commercial product to spray water on the radiator. As soon as I hit 207 degrees I pull off to cool down. That night I removed the spray heads on the Desert Cooler and cleaned them. The next day we went over Wolf Creek Pass which is 8 miles of 6% and 2 more miles of 5% grades. Again too dumb to disconnect the towed. Outside temp was 65 degrees so we got to within a mile of the top before hitting 207 degrees. Pulled over and cooled down in about 5 minutes and found we were almost over the top so no more problems.

When climbing this type of grade we try to get a very early start. Outside temps and high rpm's make a huge difference in cooling performance ut I am very glad that I have the water sprayer to assist in going over these steep grades. When we leave Pagosa Springs in a couple of weeks we will disconnect the toad before going back over these passes. Don't know what I was thinking.

Re: Engine Fan Speed

Reply #12 – August 08, 2015, 12:42:23 pm

I was about to write a post about my home made "desert cooler" that I built this summer in 119 degree Aridzona, which allows me to climb long steep passes over the Rockies at full throttle on hot days with no overheating. I have one little problem to work out, a bad solenoid valve which I already returned for a refund, then I'll test it again with the new valve to be sure I have everything right. Preliminary testing shows it works far better than I ever thought it would. I climbed Blue Mesa and Monarch Pass with it already and it provides far more cooling than my engine needs. I have to shut the thing off after a mile or so because the temperature goes down to 180 and my fan probably shuts off... which would probably save me a bunch of fan energy so maybe I should leave it on? ...Anyway, if I post the story now it'll get hijacked into another four cycle superiority thing and I'm so sick of that happening every time I even mention anything related to my engine. Maybe in a few weeks if the "superior" four cycle guys decide they don't dare accept my continental divide challenge I'll post details of how to build a desert cooler that works even at 119 degrees on the longest, steepest grades you can find. I didn't install any new switches in the dashboard, cut into any plumbing, install any new pumps or tanks, and the only new wires I ran are less than a foot long, the solenoid valve is in a very easily accessible location, and I built drains into the system to prevent freezing... and maybe I'll even install a thermal switch to make the valve open automatically... so far I have about two days labor and less than a hundred dollars in this and it's by far the most effective performance modification I've seen on a diesel pusher. I can't believe Foretravel didn't install this from the factory, but whatever... any of you interested in this relatively easy project? ...stay tuned for the details

Re: Engine Fan Speed

Reply #13 – August 08, 2015, 09:56:05 pm

To give a data point. My 8.3 which is 325hp and similar to original poster runs about 175 on the gauge normally. If I pull a long hill, it usually stays there....sometimes it creeps just above 180 to maybe 185. The only time it got any warmer than that was on a 8% down grade using the retarder full blast. Most of these long pulls were around 3 to 4 thousand feet above sea level. Though I went up to 6700 in NC and never noticed a loss of power. Fancy gap I do at 60mph in 4th gear at 2200rpm (max hp of 325) and the temp gauge never moves.

My point for all this is that I don't think the 8.3 should ever get hot on you. Maybe the m11 if it uses the same size radiator??!!

Re: Engine Fan Speed

Reply #14 – August 08, 2015, 11:27:37 pm

The Rockies are a whole different animal than your east coast hills, especially if you're pulling during the summer and with a heavy toad.

Re: Engine Fan Speed

Reply #15 – August 10, 2015, 10:44:53 am

This is really true. Speaking as someone who has driven both, the grades are the same but out west we are talking miles and miles and miles up the grades. It's something to see/experience for someone who has been on the east coast all their lives.

Re: Engine Fan Speed

Reply #16 – August 10, 2015, 03:30:00 pm

I bet that many of the overheating issues are caused on units with road crap thrown up by rear duals and trapped betweem CAC and Rad. While I was reparing the CAC yrs ago I cleaned fins in rad out and as Barry mentions totally closed in the areas on all sides so only air coming thru rad grille goes to radiator etc. Simple to do from engine access and thru the rear battery door on our models. I used belting and metal flashings. I do not get any more road spray from Duals.
JohnH

Re: Engine Fan Speed

Reply #17 – August 10, 2015, 06:16:28 pm

John,

I'm planning on enclosing my radiator too. What kind of "belting" did you use and where did you get it?

thanks
ken

Re: Engine Fan Speed

Reply #18 – August 10, 2015, 06:44:06 pm

Quote from: kenhat – August 10, 2015, 06:16:28 pm

What kind of "belting" did you use and where did you get it?

Something like this, perhaps? It comes in different widths, and is sold by the foot. I've also seen this at the local Tractor Supply (TSC).

APACHE INC. Conveyor Belt,Blck PVC,10inW,Min 3,120lb - Replacement Conveyor...

Re: Engine Fan Speed

Reply #19 – August 10, 2015, 09:51:06 pm

When I needed belting to build a new mudflap I went to a local quarry and they were glad to give me all the old belt that I wanted. It was worn in the middle on one side but they had thousands of feet of the stuff and were glad to get rid of it.
Gary B

Re: Engine Fan Speed

Reply #20 – August 10, 2015, 10:06:48 pm

Quote from: rsihnhold – August 08, 2015, 11:27:37 pm

The Rockies are a whole different animal than your east coast hills, especially if you're pulling during the summer and with a heavy toad.

It's either going to overheat or not. If temps hold stable for 10 minutes WOT up a hill, they should stay pretty stable for any longer?!? We have steep grades in the east, just not as long!

Re: Engine Fan Speed

Reply #21 – August 11, 2015, 01:10:04 am

Probably true and all of us with the big engines are just jealous that you have an adequate cooling package

Re: Engine Fan Speed

Reply #22 – August 11, 2015, 12:42:37 pm

Lots of reports and my personal experience here of higher temps not causing any issues up to a point.

Whatever you are comfortable with.

Re: Engine Fan Speed

Reply #23 – August 11, 2015, 04:25:05 pm

With new radiator from FOT, rebuilt fan motors, ISM500, worked great on I 26 in NE NC, ran mountain 65 mph up & over, temp never went above 194. Would appear clean radiator, proper fan condition sure handled the 500 hp, no problem running 1540 torque and 480 hp most of way up.
Am delighted with the results.
Engine ran little warmer down hill, 5th gear 2nd or 3rd notch retarder, kept retarder temp under 250.

Re: Engine Fan Speed

Reply #24 – August 11, 2015, 06:06:10 pm

I think the biggest difference in over heating between the eastern grades and the western grades is neither the steepness nor the length. It is the elevation. The thin air at 10,000 to 12,000 feet will not remove as much heat at the heavier air at 5,000 feet.

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