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quikduk · 09-04-2007, 07:36 AM

We took a short trip this past weekend down to Palm Desert where the temp was around 112. After we left, the coach had to pull a long 4-6 percent grade. We had the generator running with both roof airs on and the temp moved around from 185-200.

When we had to climb the Cajon Pass, the temp ran up and sat around (guessing) 119. I began to hear a garbled buzzing below the dash (temp alarm?) and made it to an off ramp a few miles up the pass where I let it idle for around 8-10 minutes.

When I got back in, (Mc Donalds break) it was sitting around 175-8. We took off and climbed the rest of the pass at about 50 mph. The temp stayed at 200.

This is the second time we have been out in this type of temp climbing grades that this has happened. I know this engine (275-C 8.3L, 800 '/#)has two thermostats and a rear mount radiator. Is it possible that there is an issue or is this normal and could I have done any damage? It seems to run fine. BTW, I did not smell coolant nor see it leaking anywhere during this time. I need to find out where that "buzzer" alarm is since it sounds like it either has a bad connection or needs to be replaced.

Any help is greatly appreciated.

quikduk · 09-04-2007, 07:36 AM

We took a short trip this past weekend down to Palm Desert where the temp was around 112. After we left, the coach had to pull a long 4-6 percent grade. We had the generator running with both roof airs on and the temp moved around from 185-200.

When we had to climb the Cajon Pass, the temp ran up and sat around (guessing) 119. I began to hear a garbled buzzing below the dash (temp alarm?) and made it to an off ramp a few miles up the pass where I let it idle for around 8-10 minutes.

When I got back in, (Mc Donalds break) it was sitting around 175-8. We took off and climbed the rest of the pass at about 50 mph. The temp stayed at 200.

This is the second time we have been out in this type of temp climbing grades that this has happened. I know this engine (275-C 8.3L, 800 '/#)has two thermostats and a rear mount radiator. Is it possible that there is an issue or is this normal and could I have done any damage? It seems to run fine. BTW, I did not smell coolant nor see it leaking anywhere during this time. I need to find out where that "buzzer" alarm is since it sounds like it either has a bad connection or needs to be replaced.

Any help is greatly appreciated.

J Walker · 09-04-2007, 08:15 AM

220 degrees won't harm anything assuming the gauge is correct. Have you cleaned the radiator recently? The Simple Green sprayed on the inside of the radiator can do wonders. Just spray it on, then run your engine to blow it out the rear. Repeat this until the liquid coming out is clear. After you finish rinse with lots of water. The valve cover vent tube should be long enough that the oil coming out does not get on the radiator. You can extend the tube so it is low enough to miss the radiator.

Ecker · 09-04-2007, 08:34 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by quikduk:

We took a short trip this past weekend down to Palm Desert where the temp was around 112. After we left, the coach had to pull a long 4-6 percent grade. We had the generator running with both roof airs on and the temp moved around from 185-200.

When we had to climb the Cajon Pass to our home, the temp ran up and sat around (guessing) 119. I began to hear a garbled buzzing below the dash (temp alarm?) and made it to an off ramp a few miles up the pass where I let it idle for around 8-10 minutes.

When I got back in, (Mc Donalds break) it was sitting around 175-8. We took off and climbed the rest of the pass at about 50 mph. The temp stayed at 200.

This is the second time we have been out in this type of temp climbing grades that this has happened. I know this engine (275-C 8.3L, 800 '/#)has two thermostats and a rear mount radiator. Is it possible that there is an issue or is this normal and could I have done any damage? It seems to run fine. BTW, I did not smell coolant nor see it leaking anywhere during this time. I need to find out where that "buzzer" alarm is since it sounds like it either has a bad connection or needs to be replaced.

Any help is greatly appreciated. </div></BLOCKQUOTE>

I think you mean 219 and that is high but will not hurt engine. You need to make sure you are running engine at or above 2000 RPM in that type of pull and weather. Just manually upshift until you get the proper RPM's.

quikduk · 09-04-2007, 08:54 AM

Whoops! Yes, I meant 219-220. I will make a note of the gear selection and keep it above 2000 RPM. Thanks.

quikduk · 09-04-2007, 09:01 AM

I meant 219-220. Ecker pointed this out.

I talked to a service mgr. for a diesel engine shop near my home and he informed me that the rear rad. design, esp. mine, has a Charge Air Cooler in "front" at the engine with the Radiator after that at the rear. There is a tendency for "muck" to get between the two and reduce airflow by around 20 percent.

His solution was to blow out each "cooler" starting with the radiator IN and then the CAC OUT. I will need to do this repeatedly until nothing appears to "fall" out between the two and on both outer sides. Then, he suggests "gently" (so as not to damage the cores) pressure wash (or strong stream) out both units until the water is clear. I like the simple green idea too since that should disolve just about anything else. 409 and the Lysol degreaser should work as well so I will try all and let you know what I find out.

BTW, this weekend I'll also be changing out belts and u-joints so I will be a busy beaver.

Thanks again.

Ken

J Walker · 09-05-2007, 05:06 AM

Just spraying on Simple Green solution from the inside and blowing it out with the engine fan is plenty good enough if done once a year. A garden sprayer is handy for reaching the entire inside of the radiator. The problem is when you build up enough grease and dirt and you get in a hurry to get rid of it all. More extreme measures like pressure washing and harsher chemical then tend to be used. There are warnings not to use a pressure washer. I will confess to using my 1000 psi pressure washer in an attempt to quickly clean my radiator but now it is only Simple Green. Do several cycles of Simple Green until you see no dirt coming out and then do this once a year. I now see very little dirt when I do my cleaning. Don't neglect extending the valve cover hose since that is the source of the problem.

quikduk · 09-05-2007, 05:28 AM

Jim,

Thanks for the tip. I noticed that hose the other day and it bothered me the way it was run and how short it was. I guess I'll change it out this weekend. Do you recall the I.D. and O.D., is it specific to Cummins or is it a generic size that is available at auto parts stores?

Thanks

Ken

Ken Roberts · 09-05-2007, 09:00 AM

Ken, per your signature with a '98 and 275 hp it sounds like you have an ISB. I had a '98 Discovery with the same great engine. Sometime in'99 or '00 Cummins had a recall to correct the "blow by" issue. Unfortunately my memory is not long enough to remember the recall #. However, go onto www.discoveryowners.com and do a search for "blow by" and you may find it. Even at this point I would bet that Cummins would take care of it at N/C if you called and made an appointment. Their top notch service is why I am back with a Cummins engine after having had a Cat for a short time. BTW, look at www.coachcare.com which is a Cummins sub that will address any type of RV repair issue at some 45-50 Cummins shops across the country. They make most other RV service ops. look like kids play. Other than body work I pretty much use them exclusively today for repairs to my rig, Ken,'04 DSDP

nhgeezer · 09-05-2007, 10:21 AM

The rear radiator mount seams to collect anything that is blown under the chassis as you drive along. My Foretravel with a rear mount radiator began to run warmer than usual coming up from Florida this past June. An inspection found that pieces of a black garbage bag covered more than 50% of the radiator. Cleaned that off and then washed the core with Simple Green and the temp was back down where it belonged.

1990 Foretravel

quikduk · 09-05-2007, 12:05 PM

Ken:

I'll bookmark and check out the links. Thanks for the tips.

My engine is a 275-C since it has the mechanical Bosch fuel injection pump. The ISC's had electronic fuel injection pumps. My engine is also the 8.3L and in my GS configuration, it was called a Gulfstream Sun Voyager Bus - Platinum Edition which denoted the larger 800 ft/# torque model. The others in the line at the time used the 660 ft/# torque engines even though the HP was supposed to be the same. This was only available in this model IF it was the 8362 model (36 feet long - actually 36'-10").

Thanks again.

Ken H.