Check engine light came on and temp spiked at 225 on a steep grade

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Check engine light came on and temp spiked at 225 on a steep grade

September 01, 2016, 08:59:35 am

I experienced an overheat and check engine light event while coming up the last steep grade into Boone, NC where we live. We have to take this route every time we take the motorhome in or out and I have never had an overheating situation during hot or cold weather. This stretch of road is about 8 miles with varied grades.

When coming up this or any other hill I let the coach transmission do its thing. I leave the pedal on the floor and the coach downshifts/upshifts as needed. Speed varies between 40 – 45 MPH with one particular hill slowing the coach to 35MPH.

'Normal' warm weather temp (since we've owned the coach) seems to be between 185 – 200 degrees. I scan the gauges constantly when driving. I saw the temp spike to 225 and the check engine light came on.

I immediately pulled over and in a few seconds the temp returned to 200 and the check engine light turned off. I got back on the road and this sequence happened one more time a few minutes later. By this time I was at the crest of the hill and everything was normal after that.

I see no leaks of any kind. MOT did a coolant flush and replacement last June when I bought the coach. Levels are normal on the coolant overflow tank...on the hot line when hot, on the cold line when cold.

Oil and filters were changed last month. Oil level is full. The air filter was also replaced during the oil service last month. The coolant overflow was a bit low (a few inches on the overflow tank when cold) when I had the fluid/filter changed at so they topped it off

When this happened I remembered that the PO had designed and installed a supplemental air filter. I need to track this down and check it. That filter has never been replaced. Could this be causing the overheat?

I'm headed out to the coach this morning and will check the radiator to see if the exterior needs flushing.

What else should I be doing to track this down? Thanks all!

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #1 – September 01, 2016, 09:08:22 am

Jeff,

If concerned about air flow/an air filter, check your AIR FILTER MINDER READING.

And, remember, you can easily verify that the filter minder is reading by pulling off the hose at the other end and sucking on it. That should peg the filter minder reading at max. Then, just push the button on the bottom of the air filter minder to reset.

Normal procedure when coolant temperature continues to climb is to select a lower gear and back out of the throttle. Keep RPM's up, but not at WOT.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #2 – September 01, 2016, 09:10:44 am

Quote from: wolfe10 – September 01, 2016, 09:08:22 am

Jeff,

If concerned about air flow/an air filter, check your AIR FILTER MINDER READING.

And, remember, you can easily verify that the filter minder is reading by pulling off the hose at the other end and sucking on it. That should peg the filter minder reading at max. Then, just push the button on the bottom of the air filter minder to reset.

Normal procedure when coolant temperature continues to climb is to select a lower gear and back out of the throttle. Keep RPM's up, but not at WOT.

Thanks Brett, WOT?

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #3 – September 01, 2016, 09:12:36 am

Quote from: Jeff & Sandy – September 01, 2016, 08:59:35 am

When this happened I remembered that the PO had designed and installed a supplemental air filter. I need to track this down and check it. That filter has never been replaced. Could this be causing the overheat?

I'm curious about the "supplemental air filter." Any idea why the PO thought there was a need for one?

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #4 – September 01, 2016, 10:12:05 am

Quote from: D.J. Osborn – September 01, 2016, 09:12:36 am

I'm curious about the "supplemental air filter." Any idea why the PO thought there was a need for one?

Me too. i am not sure why it was installed.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #5 – September 01, 2016, 10:18:51 am

WOT= Wide Open Throttle.

Yes, the previous owner of Jeff's coach did a LOT of modifications.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #6 – September 01, 2016, 10:25:54 am

Got it, thanks Brett.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #7 – September 01, 2016, 10:44:53 am

Quote from: Jeff & Sandy – September 01, 2016, 10:12:05 am

Me too. i am not sure why [the supplemental air filter] was installed.

It would certainly be interesting to see more details (and pictures) as you get it figured out.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #8 – September 04, 2016, 12:03:30 am

Since the check engine light came on that means it was not a temp gauge error. It actually did get hot.
I would start to focus on the radiator. Cleaning the outside like you are planning is a good first thing to do.

Then maybe think about the hydraulic fan system as I have seen other U300 '92-'94 year owners need to replace pumps and motors. I'm not too much help here as my U300 is the older rear radiator with a direct drive fan (without hydraulics). Maybe others who have been through it can help. The forum search function should help you find the experiences others have posted and what their symptoms and repairs were.

Some might suggest the coolant pump on the engine but since it cooled down right away when you pulled over I doubt it.
I also doubt the air intake filter would cause overheating like that - it would kill your power first due to low turbo boost. Do you have a VMS system? They are quite handy as it would tell you your boost pressure along with a host of other things. But it wouldn't tell you anything about the hydraulic fan system though.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #9 – September 04, 2016, 12:39:38 am

Clean radiator, carefully and closely look over blower fan on radiator, possibly check coolant thermostats. When was last time coolant was flushed and replaced?

I never climb steep hills at WOT, and normally downshift manually before the Allison would do it on it's own.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #10 – September 04, 2016, 02:11:54 am

We also take it easy on steep grades and also long pulls. We shift down manually and also watch the "load" on our Silverleaf.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #11 – September 04, 2016, 02:47:36 am

I have been stifled many times before on my stories about old Rv problems. I was fortunate to have several owners of Foretravels I sold that owned fleets of hard working diesel trash trucks and interstate truck fleets.

The warning lights turned out to be extremely pessimist in their settings.

I had multiple customers leave their home bases in the desert southwest in the middle of the night so that the check lights to not come on that I got together with the engine makers and chassis makers to quantify the warning lights settings as they did not match my truck fleet owner experiences.

I rode along with Garrett bosses garbage truck fleets one day. Normal engine temp was 220. Trans temp 250.

Same thing in a gillig phantom intercity RTD bus.

Now a 6v92's wet sleeve supercharged and turbo'ed design with the intercooler under the blower may be different BUT I personally drove a dozen of them up Baker grade at 235+ for ten miles without incident. Yes the light came on at 225. Shutdown was 250 range? Forgot exactly as Detroit and Foretravel finally raised the warning lights turn on points after my testing 30 years ago.

Yes they(Foretravel) had the in house ability to reprogram those functions.

The original engines were 277hp and 840 torque. I had them change the 1989's to 300/820 for sales reasons.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #12 – September 04, 2016, 09:53:25 am

Ever wonder why they were originally coined "idiot lights"?

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #13 – September 04, 2016, 09:57:03 am

Bob where you the test platform for FT, why would you have them change the engine from 277 hp/840 torque, to 300 hp/820 torque.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #14 – September 04, 2016, 10:49:29 am

Quote from: Bill Willett – September 04, 2016, 09:57:03 am

Bob where you the test platform for FT, why would you have them change the engine from 277 hp/840 torque, to 300 hp/820 torque.

The 277hp cost me a lot of deals. Foretravel u300 owners SOB buddies would tell them "well, I got a 300hp engine in mine."

The trans also was nominally rated for 780 pound feet of torque and the Allison man had to sign off on the over the max rating for Foretravel. No real problem as the coaches weight was low enough that the designs actual reserve was not exceeded.

I remember standing in the back of the meeting room for the unihome introduction in October 1987 talking to the Detroit and Allison man at the same time.

My question to the Detroit man was how to get the engines rating to 300hp for the bragging rights of the future owners.

The Detroit man took out a small folding spec sheet from his suit coat pocket and said "well I could lower the torque and raise the hp?"

The Allison man said it would help his overly high torque rating so we three agreed to lower the more powerful 277/840 to a easier selling 300/820.

Never did tell CM and Ray and Don Lee what we had cooked up in the back of the room.

If I owned an early u300 I would have Detroit reset the DDEC setup to the 277/840 as in a side by side race the 277 pulled the 300 a fair amount.

Weird true story.

300 cat was 743 torque so the Detroit was way faster and had an ATEC trans the 300 cat did not have.

The ribbing from the u300's buddies really hurt their feelings.

As far as I know they should be able to be reset inexpensively to the 277/840 from the 300/820

Power on any diesel is the torque not hp.

That's why the changes I did to our m11 freed up the torque at 10-1500 rpm.

I build a specific brand of Austrian dirt bike four stroke engine much larger than the oem setup was and change the cam to accentuate the low and mid rpm power and to eliminate the "hit" in the powerband, which is a rapid increase in the engines hp in a small amount of rpm increase.

Better fuel mileage, lower noise, longer engine life is the result.

The 277/840 pulled the hills better and if memory serves me got better mpg as it downshifted less.

Defintely faster...

Sorry guys. Blame me. Customers demanded a 300 rating before they would buy it

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #15 – September 04, 2016, 04:11:56 pm

Guys,

We have strayed a LONG ways from the topic on this one: "..... overheat and check engine light event/I saw the temp spike to 225 and the check engine light came on. "

Lets get back to the topic.

Thanks.

And, Jeff, before assuming there is something mechanically wrong, I would sure give using different driving techniques a try. From my earlier post: "Normal procedure when coolant temperature continues to climb is to select a lower gear and back out of the throttle. Keep RPM's up, but not at WOT."

Let us know if the overheating continues even with proper driving techniques.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #16 – September 04, 2016, 04:24:43 pm

Quote from: wolfe10 – September 04, 2016, 04:11:56 pm

Guys,

We have strayed a LONG ways from the topic on this one: "..... overheat and check engine light event/I saw the temp spike to 225 and the check engine light came on. "

Lets get back to the topic.

Thanks.

And, Jeff, before assuming there is something mechanically wrong, I would sure give using different driving techniques a try. From my earlier post: "Normal procedure when coolant temperature continues to climb is to select a lower gear and back out of the throttle. Keep RPM's up, but not at WOT."

Let us know if the overheating continues even with proper driving techniques.

Noted, and thanks Brett. I always learn a lot when I chat with Hans and we chatted about this right after it happened and he gave me the same advice about managing the gears and rpm's. He doesn't seem to mind my dumb questions and neither do you. Thank you.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #17 – September 05, 2016, 07:08:38 pm

The only question that is dumb is the one you don't ask! More knowledge from answered questions is always better. That's how we learn more about our coaches. Lots and lots of knowledge out there for the asking.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #18 – September 05, 2016, 07:59:05 pm

I would make sure the radiator is clean and it could be your fan isn't ramping up. If it heats up again check the fan, that it is really reving up. It should be making a lot of noise.

Re: Check engine light came on and temp spiked at 225 on a steep grade

Reply #19 – September 06, 2016, 12:44:08 pm

Install an oil temp gauge.

225 degree's on a hot day isn't too out of the ordinary.
The fan clutch on my old Pete' didn't kick in until the temp got to 220'.

Not sure where the fan is supposed to engage on your application,
you may want to check whatever controls the fan (also). pc

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