94 8.3 Cummins overheating

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94 8.3 Cummins overheating

September 05, 2022, 09:22:40 am

I have a 1994 Grand Villa with a 8.3 Cummins that is overheating. I do not think that the fans ever ramp up to high speed. Here is what I have done so far... Changed the two thermostats, hydraulic oil and the 3 stacked filters, changed the sending unit to the temp gauge, changed the sending unit to the speed control valve and changed the speed control valve. I have now unplugged the valve and still no ramp up in speed of the fans. If I spray the radiator with water the engine cools rapidly so I really think I have a fan speed issue. I have read many posts about over heating while driving over a mountain pass, this is not the issue. It is overheating in 80-90 degree outside air temp, no toad on flat Texas highways. It takes about 20 miles to go from 180-225. I think that the alarm sounds just over 225. Both fans seem to be turning at the same speed...The way that i understand the control valve is 12v to the valve for low speed then when it reaches temp, 185 I think, it cuts power and the valve springs open. This is driving me crazy!....What am I missing?

I have tried calling tech support at FOT, even though I pay my fee every year.......they will not return a call

Re: 94 8.3 Cummins overheating

Reply #1 – September 05, 2022, 10:13:47 am

I don't know what you mean by unplugging the valve. If you stop the fluid from going through
the hoses the fans will ramp up. Are you sure you are overheating. My last trip the Silverleaf computer
wasn't working and my temperature gauge was reading high so I stopped and went back and checked
the engine and it was fine. When I parked for the night the gauge was reading 250 and the engine
wasn't over heated. The gauge always had read hot so I changed the sender just before the last trip,
so I guess the sender wasn't the problem.

Re: 94 8.3 Cummins overheating

Reply #2 – September 05, 2022, 10:36:40 am

My understanding of the fan speed valve is with 12v applied to the valve the fans run at low speed, with out 12v they ramp up. I disconnected the power to the valve and they still seem to only run in low speed. Also they seem to blow out from the engine compartment to the outside, that does not seem correct? do you know? From the outside looking toward the engine the fans are turning counterclockwise. I am pretty sure it is overheating. Gauge and alarm

Re: 94 8.3 Cummins overheating

Reply #3 – September 05, 2022, 10:39:49 am

Absolutely, air flow should be from OUTSIDE toward the engine room.

Said another way, the fans should suck air through the CAC and radiator and discharge it to the engine room.

Have any of the hoses been "rerouted"?

Re: 94 8.3 Cummins overheating

Reply #4 – September 05, 2022, 10:40:57 am

Sounds like the gauge is good or the temp would not come down with the hose water,make sure the radiator is clean,make sure the air filter is not plugged up,get one of the temp guns at Lowes so you can take temp of the engine,when it gets hot does it have good power?,are both fans turning,have you changed the fuel filters,is all the air out after changing the thermostats.Do that and get us an update,sounds like a simple problem.

Re: 94 8.3 Cummins overheating

Reply #5 – September 05, 2022, 10:46:44 am

Was answering when you made post number 2,if fans are blowing out something got rerouted by mistake,someone with your exact setup will hopefully chime in,my 8.3 system is all hyd no 12 volt control that I know of.

Re: 94 8.3 Cummins overheating

Reply #6 – September 05, 2022, 10:47:40 am

If you take the hoses off the valve and plug them, the fans should go to high speed. If they
don't then you have another problem.

Re: 94 8.3 Cummins overheating

Reply #7 – September 05, 2022, 11:11:34 am

Quote from: wolfe10 – September 05, 2022, 10:39:49 am

Absolutely, air flow should be from OUTSIDE toward the engine room.

Said another way, the fans should suck air through the CAC and radiator and discharge it to the engine room.

Have any of the hoses been "rerouted"?

I have definitely confirmed that they are blowing out. now to figure out why. I changed the speed valve but am sure I put them back where they were....or I thought that I did! I have the hydraulic fan system drawing in the manual and am retracing.... Am I correct about the speed valve? 12v to run in low 0v to run in high?

Re: 94 8.3 Cummins overheating

Reply #8 – September 05, 2022, 11:18:30 am

Even if you solve the hi lo voltage problem the fans are still running backwards,try reversing the 2 hyd hoses that you thought you put back the same,won't hurt and you can always switch them back,when that is fixed then work on the speed part.

Re: 94 8.3 Cummins overheating

Reply #9 – September 05, 2022, 11:28:43 am

Karl, sent you a PM

Re: 94 8.3 Cummins overheating

Reply #10 – September 05, 2022, 11:33:05 am

Quote from: John44 – September 05, 2022, 11:18:30 am

Even if you solve the hi lo voltage problem the fans are still running backwards,try reversing the 2 hyd hoses that you thought you put back the same,won't hurt and you can always switch them back,when that is fixed then work on the speed part.

Correct! I am about to switch the hoses on the speed control valve. If that is the direction problem....it might solve the whole thing. The hoses have numbers but the diagram from FOT does not.

Re: 94 8.3 Cummins overheating

Reply #11 – September 05, 2022, 12:58:31 pm

The fans on our U240 default to high with no power to the 2 speed solenoid.

Re: 94 8.3 Cummins overheating

Reply #12 – September 05, 2022, 01:40:01 pm

Quote from: Dave Larsen – September 05, 2022, 12:58:31 pm

The fans on our U240 default to high with no power to the 2 speed solenoid.

Thanks! That's what I thought from the wiring diagram.

Re: 94 8.3 Cummins overheating

Reply #13 – September 05, 2022, 01:44:58 pm

Quote from: Karl Shurtleff – September 05, 2022, 11:11:34 am

I have definitely confirmed that they are blowing out. now to figure out why. I changed the speed valve but am sure I put them back where they were....or I thought that I did! I have the hydraulic fan system drawing in the manual and am retracing.... Am I correct about the speed valve? 12v to run in low 0v to run in high?

Ok I think that I have it solved! The guy that changed the valve (that would be me) switched 2 lines. Reversing the 2 lines fixed the incorrect rotation and seemed to drastically increase the speed of the fans. Now for the test drive....

Re: 94 8.3 Cummins overheating

Reply #14 – September 05, 2022, 04:29:41 pm

Ok after the drive it is much better but still not where I think it should be. It is running well over 210 and confirmed with a laser thermometer. I will look for a more accurate laser as I am not sure of the accuracy of the one that I have.. Not sure where to go next unless I pull the radiator and have it rodded out?

Re: 94 8.3 Cummins overheating

Reply #15 – September 05, 2022, 08:35:29 pm

How about a photo tach on the fans. Inexpensive on Amazon or free for iPhone or Droid. ‎Strobe tachometer (RPM meter) on the App Store You can check to see if both speeds are working.

You temps are too high.

Pierce

Re: 94 8.3 Cummins overheating

Reply #16 – September 07, 2022, 07:45:11 am

Please note, I have split off RevRick's issue as it is an entirely different drivetrain.

This topic is only about the Cummins 8.3 with side radiator.

Thanks.

Brett/moderator

Re: 94 8.3 Cummins overheating

Reply #17 – September 07, 2022, 08:46:48 am

I have the same 280 with 8.3. I have same problem. I have done everything you have done. Plus I put a rocker switch with led to turn on high fan from drivers seat. I wired it so the LED will come on anytime the High fan is on. That way I can monitor temp verses high fan. I have even replace radiator. I hope you resolve the issue! I believe it is either a airflow issue at high speed or the radiator is just not large enough. I just bought a thermal imaging camera. Once I get my basement rebuilt. Back to the overheating problem.

Re: 94 8.3 Cummins overheating

Reply #18 – September 07, 2022, 09:33:30 am

Karl Shurtleff. In addition to calibrating you infrared pyrometer against a pot of boiling water, I had a thought: slide underneath and squeeze the lower radiator hose with your hand. If you can squeeze it mostly shut you might find that radiator hose is collapsing from the suction of the water pump. That'll make your engine overheat.

Re: 94 8.3 Cummins overheating

Reply #19 – September 07, 2022, 10:34:23 am

You need to verify that the fans are coming up to speed and here's a way. I can not, personally, tell the difference between low and high fan speed by observation. My coach, a 96 flat nose, same drivetrain, driving from S. Tx through the Rockies, Cascades, just made the trip well loaded and running hard no toad....never over 200 degrees. The proper fan rpm info is floating around, hopefully a forum member can point you to it.

Amazon.com: AGPtekÂ® Professional Digital Laser Photo Tachometer Non Contact...

If the fans are working properly then, after following the other suggestions listed, I'd maybe take a look and make sure the prior owner did not tinker with the fueling, timing etc in a quest for more power. Verify the aftercooler is not leaking at fittings or body, and radiator is not blocked, on outside and between aftercooler and rad. Verify there is no brake drag. Check your shift pad for transmission codes.

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Re: 94 8.3 Cummins overheating

Reply #20 – September 07, 2022, 01:17:09 pm

Quote from: wolfe10 – September 07, 2022, 07:45:11 am

Please note, I have split off RevRick's issue as it is an entirely different drivetrain.

This topic is only about the Cummins 8.3 with side radiator.

Thanks.

Brett/moderator

Thanks Brett, I was trying to figure how to do that but couldn't.

Rick

Re: 94 8.3 Cummins overheating

Reply #21 – September 07, 2022, 01:54:58 pm

Quote from: RevRick – September 07, 2022, 01:17:09 pm

Thanks Brett, I was trying to figure how to do that but couldn't.

Rick

Just go to the appropriate section ("Foretravel Tech Talk" for example) then click on "New Topic" at upper right to start a new discussion.

Re: 94 8.3 Cummins overheating

Reply #22 – April 16, 2023, 03:36:09 pm

Any update?

Re: 94 8.3 Cummins overheating

Reply #23 – April 16, 2023, 06:07:50 pm

Quote from: Jeffsjag90 – April 16, 2023, 03:36:09 pm

Any update?

I note that RevRick hasn't been on the forum since December. If he doesn't respond in a couple of days, you might try PM-ing him to get his attention.

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