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Engine over heating
Greetings from the trip from hell….. Last year leaving Scottsdale for home in Orlando my check engine light came on for radiator temp. Pulled over high speed fan seemed to be working and radiator was full. Happened couple more times on that trip with same result. Took to Prevost jax and no problems found. Next use was this past week. Left Orlando and got north of Atlanta and light comes on. Temp was around 225 and only way it would go down was keeping the turbo needle at half boost or better. The fan appeared to be running in low speed. Next day drove to Nashville. Lucked out going up monteagle with construction so we creeped up at low turbo. 2 miles from Prevost Nashville got another check engine. Was in heavy traffic and suspect fan was not operating. Prevost Nashville spent the day Friday looking at it. They said fan clutch, replaced 2 years ago, was good. Checked all wires. They replaced temp sensor and another sensor. I had asked them to change everything from the thermostat to the fan clutch. They did not. They thought the problem might be in the Ecm
Leaving Nashville we traveled less than 100 miles before light came on. Fan was not operating and temp was around 230 coach seemed to operate ok as long as I kept turbo boost no greater than 50%. Stopped in Memphis and had the fan clutch bolted. That worked well to Oklahoma where bolt broke or etc. limped into Oklahoma City and coach is at United engines the Detroit dealer.
Appears I am in for Detroit saying it is a Prevost problem and Prevost saying it is a Detroit problem. All we want is our nearly problem free coach back and finish our trip to California. Any ideas?
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32 Replies
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Dave,
It’s dangerous when I start trying to give advice but I assume you are running the dash a /c ? If not, I would engage it at all times… it is my understanding that this encourages the clutch on the radiator to be engaged at all times. Thus hopefully, a reduced temp?
Pres
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If you have high temps my first advice is to stop driving. The quickest way to convert your engine to junk is to overheat it.
I understand nobody likes to stop, but the risk versus reward ratio highly suggests the benefit of limping along is far outweighed by what it will cost if you ruin the engine.
Having said that your fan can be electrically locked. On an H3 model break the 85 tabs off of the relay numbers R84 and R85 and you electrically lock the fan clutch. Using the tabs and bolts is very temporary (as is using the relays).
Use this to get you to a place where the fan clutch issue can be resolved, either with a new clutch or repairs to the circuits to the clutch. Hope this helps. BTW, you can verify the clutch is locked by trying to turn the fan when the key is on.
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This will not help you with the over all cooling problem but in the future you can lock the fan clutch in high speed without risking breaking the bolts. Remove the relay for the fan and break off the 85 blade and it will be locked in high until you replace it with an undoctored relay. I keep one with the 85 blade removed just in case I need to plug it in during an emergency.
Davy
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Thanks for the great advice. Detroit says it is a bad fan clutch. Ecm is fine. Replacing with new one tomorrow. Interesting that Nashville Prevost could not have figured this out. Clutch being replaced is 2-3 years old with less than 25k miles on it. Sure hope this cures my problems. Thanks again. Definitely going to learn where that relay is and have an extra handy.
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Jon wrote: “fan can be electrically locked. On an H3 model break the 85 tabs off of the relay numbers R84 and R85 and you electrically lock the fan clutch. Using the tabs and bolts is very temporary (as is using the relays).”
Good topic for the care and feeding seminar at Jeff’s in a few weeks. Jeff should have a bunch of those relays on hand, I suspect a number of us are going to want to buy one and break the 85 tabs off.
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No one ever responded as to whether or not my thought of running the dash a/c engaged was a good idea or not to keep the clutch engaged. Do most of you allow the temp to hit 210 /215 and await the clutch to engage to bring it down or do you take other action? I drive very softly and watch the turbo even when on cruise…I may be an old fogie but I run 64 / 65 MPH and love it. If I want to go fast, I get in the ‘Vette… I used the word ‘Vette just to get Jon riled…
Pres
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Pres, I understand why you suggest the use of dash air. When it is engaged I believe the fan clutch is locked in the high position. I suggested locking it electrically with the relays because that is how Prevost suggests dealing with a failing clutch.
I should point out if the clutch has an internal electrical failure that method will not work and in that case you should lock the clutch using the tabs which are not intended for a long term use, or stop driving.
One possible emergency procedure is to keep the bus geared down and drive slow but to stop if the temps rise.
Dick, that is indeed part of the seminar and it is coach specific. The relays I mentioned are for the H3. Your relays will be a different number, R78 and R79 for the X series. We are hoping we get a lot of questions and discussions so we do cover as much as we can. We think our outline is fairly comprehensive but we do want to cover as much as possible.
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Dave,
You’re at the right place, United Engine does good work and we have a PC member with lots of clout there if you have trouble.
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Anybody that travels with there coach and does not have one of the relays as a spare is looking for trouble I carry spare relays of 12 volt and 24 volt just in case ,and one with the tab broke off
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Peter
Given your XLII, which relay part #’s do you carry as sounds like excellent advise to carry extras….. I will be in Stuart this week and add to my list…. My coach temp always runs to the high side of the gauge and cycles up and down as the clutch engages…
PS. sent you pictures by PM….
Tks,
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Brady,
Your series 60 engine should typically show around 200 on your temperature gauge. It usually will cycle a little above or a little below that reading. On occasion such as hot days, during a hill climb the needle might climb to just below the 210 degree mark, but when it does you should observe it cycle back down. It should not stay there.
I believe your DDEC is set to turn on the low speed radiator fan at 204 degrees at which point you should see the temp drop back a little. On a hard pull you might see it climb to the high speed fan setting of 208, but at that point you should observe the temp falling back. I’m not sure what you mean about it reading on the high side of the gauge, but the temps above are normal and are approximately at the top center of the gauge.
For spare relays the most common are the black cube relays used through the Prevost chassis. Get them from Prevost because they have a relay or diode installed that makes them better for some of the applications. Last time I bought them from Prevost I bought a bag of 10 and they were pretty cheap, around $4 each.
Liberty and the Prevost Chassis have other types of relays also and it does not hurt to have at least one of each type as a spare. Liberty can help you with supplying those, or you can get them from WW Grainger but you have to research which ones you will need.
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Truk,
Is there a new member in OKC that I haven’t met? A member with lots of clout?
Loc
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You’ll recognize him, Loc. He usually wears Tennessee Volunteer orange.. I think he has a Jeep that color.
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It’s about time you woke up Locnest….
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Thanks for the great advice. At the risk of sounding stupid how does one figure out which tab to modify? Do you modify it on both the low and high speed relays.
United engines was awesome! Finished the job and we will be west bound in the morning. Austin, the technician, diagnosed the problem in 30 minutes. Prevost Nashville spent a day and 15000 of my money and found nothing. Apparently they did not check fan clutch because it looked new. …….
when finished austin gave gave me his cell and email and asked me to email how rest of our trip goes. What a rgreat representative for united engines.
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