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Engine over heating
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Jon
As indicated, Troy says on my engine, 2007 chassis (post EGR with emissions) they run this temp and on the high side. My previous 2003 coach, the temps were as Jon indicated.
Any owners with “emission engines’ experience these higher engine temps?
Thanks,
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Dave,
I believe I would be looking for some credit from Prevost.
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A fan clutch issue become obvious from the driver’s seat. If a driver learns the patterns of his gauges, in this case the coolant temp gauge he will note cycling up and down. I know gauges can have an error, but under normal level ground conditions regardless of outside temps (unless extreme) when fully warmed up a coach is going to have a swing between a low reading and a higher reading. This cycling is normal and is due to the fact DDEC turns off the fan when the temp drops below a certain point, and then when it climbs to the low fan speed set point it cycles back on.
Typically a coach will have a low point of just below 200 degrees and a high point just above when the engine is moving the bus on a level road. I know those are accurate temps on coaches, even with the EGR, but I am trying to confirm if the set points are higher with later model emissions equipment. BTW, those can be reset, but I do not know if Detroit dealers are allowed to alter what might be an emissions changing value.
When climbing a hill or operating under high power conditions the temperature will reach around 210 degrees and then cycle back down. That higher temperature is because the low speed fan operation is inadequate so the second high speed is engaged. Under even hot ambient temps, climbing a steep long hill the driver should note when the temp hits that higher value and the high speed kicks in the temp should cycle back down. It is when the temps do not cycle back down that there is a problem.
But when the fan clutch is failing it will not keep temps cycling as described above. Obviously some things have to be ruled out before suspecting the fan such as coolant level and belt condition or tension. But if everything else checks out then the fan clutch can be checked by applying power to each speed. If the low speed is engaged the fan can be turned but with resistance. If the high speed is engaged it will be locked. The service technician should be easily able to test it.
The question regarding the relay is the tabs are marked with numbers molded into the plastic case. Break off the 85 tag to engage the clutch. If you want to test the fan clutch yourself use a modified relay in place of the fan relays and turn on the ignition. As stated previously in low speed engaged you should feel resistance to turning, and in the high speed engagement the fan should be locked.
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What tab # do you break off for low speed. Thanks Murph
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As stated above to select which fan speed you want locked, you insert the modified relay into the space for the original relay. Each fan speed has its own relay.
Do not think you can somehow benefit by locking the low or high speed fan on. That is to be done only in an emergency situation and should be considered temporary.
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As a result of this thread and an email exchange with some folks I found a lot of bad information is being provided by people who should know better. I am sure I give out lousy advice at times and would hope I get corrected because sometimes bad advice is worse than no advice.
The reason for the email exchange that has prompted this post is a member asked a legitimate question about what temps he should see for his specific coach. He had asked a couple of people including the maintenance guru for his conversion and he was told his temps were normal. I had no experience with his model year so I started doing research because coolant temps are important.
In the meantime he asked a higly placed individual with Prevost service the question and again was insured his temps were normal.
I was able to access the Detroit service manual for his engine and found some information to suggest to me his temps were in fact on the high side. So I finally was able to access the Prevost shop manual for his specific model year and the temps from the table in the shop manual was consistent with the information in the Detroit shop manual, and was different than what he was told was OK by his converter and Prevost.
I am glad we had the continuing exchange of emails because it appeared the information he was getting was little more than an opinion or a guess. I am not glad information he got from Prevost was inaccurate. I also spoke to Prevost and the information I got was more correct, but I still got the sense the man providing it was making an educated guess.
It is distressing to learn owners cannot get precise information from people at Prevost. It is bothersome to me that I may be doing the same so if I dish out bad information I hope everyone dumps on me. In the meantime the owner is running at unusual temps, but as we all know the problem could be in his gauges, or he could have a real problem. At least now he has facts so he can decide his next step.
My guess is if anything is to be taken from this, Carguy Dave did not get the expertise he should have during his visit to Nashville, and information provided to me and others by Prevost is less than accurate, meaning we have to be very specific when asking questions, and even more specific when asking how the person came up with the answer. It is going to put some people on the spot who might be guessing, it is going to irritate some people who aren’t happy you are questioning their answer, but we cannot act properly if we are acting on bad information.
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Well Said
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You are right on Jon , people can get bad info from anybody , that’s why this is a great site, My temp gauge in the middle is 190 , Mine pulling trailer is about 200 to 204 ,heavy pull it will climb just little bit to 208 then back down, have never had it go to 210 except when I broke a belt because of a rock.!!!!! Saw temp go up and pulled over and sure enough broken belt!!!! Pulled over and fixed it put new belt on all good after!!!!! Important to know what your gauges do ,, including the air gauges, turbo boost gauge
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Jon
i have been reading several threads and I have two questions. Has there been issues in the older Marathons with the Jenn Airei refrigerators? So far mine working good. Does my vintage 1995-6 XLV have the relay that can engage the hi speed fan in the event it is needed on the road? Can not find one in my box. And finally my DDEC readout has just gotten unreadable. Is there a reset or am I looking at something worst? What do you think I should do. Thanks friend. -
Tony,
I have no experience with the Jenn Air refrigerator but the absence of remarks posted on the forum suggest it has either been reliable, or not that many were installed.
As to the engine temps, if you have the Series 60 with the two speed clutch you have two relays in the rear electric box that can be modified by breaking off the #85 tab to lock the coach radiator fan electrically into the low or high speed. If you have to do that to control temps that should not be viewed as a repair, but a temporary means of allowing you to drive somewhere for service. Those relays are listed on the legend showing the number and location of relays and CBs in the rear electric box.
Do not go by the numbers listed above because I think they are H3 specific.
I cannot answer your question about the Detroit display. That might be one that ETLC needs to look at because it could be the display, it could be connections or something as simlple as a bad ground.
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Does anyone know how to test the relays with a meter to rule out a bad one ? Please explain ? Also, there are some relays that have a reset button on them. Do these ever fail ? Are all of My relays 12V on a 96 XL ?
Safe travels,
Rocky
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Re: relays with a reset button? Are you sure they are relays or are you looking at circuit breakers?
Testing relays involves pulling it and checking the coil for continuity. Then using an ohm meter power the coil and make sure you have little or no resistance across the points.
Or do what just about all of us do. If you suspect a relay is bad, put in a new one known to be good. If the problem that made you concerned about the relay goes away the relay was bad.
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Please take other posts to a new thread or we’ll have to close this.
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Jon
Thanks for your insight. Thought I had the Amana till I looked closer. Will trust my Jenn aire to keep on keeping on. Don’t have an overheat problem, just thought I’d be prepared in case of an issue. I looked at the schmatic on the rear door and don’t see the relays you spoke of. My general observation is free fan till about 195-200 degrees and a locked fan till temp drops. I will check the connections on the DDEC. Engine is running great. Hope you are well. We need to get together again and talk Airplanes and Buses.
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