Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 15, 2025 ...

To Quote Bob: "Every motorhome owner is too paranoid about the temp gauge IMO. I ran all these really hard for hours myself to test them as they were my demos and owned by foretravel and the other companies and never had a single issue and neither did any of the customers I ever educated. Like I said if it runs 210 up a hill at 70 degrees and 240 at 100 degrees it's relative and within the design limits of the coach."

With many years experience with the DD engines, I see the 240f temps as one of many reasons Foretravel went broke, nothing like a salesman to help sink you.
No one runs a DD into that temp range without it getting shut down by the DDEC system.
Just one more reason for all the humor.
Dave M

To Quote Bob: "Every motorhome owner is too paranoid about the temp gauge IMO. I ran all these really hard for hours myself to test them as they were my demos and owned by foretravel and the other companies and never had a single issue and neither did any of the customers I ever educated. Like I said if it runs 210 up a hill at 70 degrees and 240 at 100 degrees it's relative and within the design limits of the coach."

Now I am somwhat confused, as I frequently worry about my C8.3 Cummins' temp as I approach the crest of a steep and/or long grade and the engine temp creeps up toward 205-210. The temp alarm begins chirping at about 210 and is full blown by 215. Are you saying that I can ignore the alarm and don't have to pull over to let the temp return to normal (i.e. 190-195) levels? Or were your comments restricted to CAT and Detroit Diesels?

If what you relate is correct, even for Cummins engines, I would want to shut down (greatly reduce) my alarm volume, as it is irritating at the least and anxiety-producing at the most.

I REALLY appreciate you sharing with us your experiences with many FT's over the past couple decades. It has enriched my understanding of this great product.

Dave, I'm betting Bob treats his own U320 the same way he has discussed. One has to go by their experience and his has been that pushing temps above 210 has not been harmful. I'm guessing that your vast experience related to high running temps with diesel engines on generators and OTR trucks is much more extreme than the occasional high temps we experience with our coaches. I'm still going to go by your recommendations just because I don't want to make an expensive mistake, but I'm sure Bob's experiences dictate a different approach to the high temperature running of our Foretravels.

I wish I could relax and just cover up the coolant temp gauge, but that will never happen.

Bob, Do not confuse a marine engine with a highway engine, while they look the same, they have vastly different horsepower ratings BECAUSE they have a massive cooling body of cooler water, and NOT a minimal sized radiator.
Dave M

You can get away with 240 deg F for a little while, but you're almost certainly increasing piston ring wear, promoting cylinder liner scuffing, burning more oil, oxidizing your oil, and increasing carbon buildup in your piston ring grooves.

Engine cylinder liners are designed so that the heat transfer across the liner, from combustion chamber to engine coolant, maintains the temperature at the inside top of the liner to 400 deg F or less. If the temp exceeds 400 deg F, then the oil film at the top of the cylinder liner will flash off and the top ring on the piston will momentarily weld itself to the cylinder liner on the combustion stroke where the top ring is under the greatest load. This is the Top Ring Reversal condition and it's the most critical thermal loading in the engine.

If the manufacturer says that you're coolant temps are good to 210 deg F and derates at 215 deg F and you override this and continue to 240 deg F, then the heat transfer across the top of the cylinder liner will be impacted. The inner cylinder liner wall will see a corresponding increase in temperature and you run the risk of flashing off the oil film. So it's not a "relative" temperature issue. It's an absolute temperature issue. You can only let the top inner surface of the cylinder liner hit an absolute max temp that's less than the oil flash temperature spec, regardless of outside air temperature. Otherwise you're absolutely increasing wear on the engine.

Can you get away with it for a short period? Probably, but you're definitely shortening the life of the engine.

David Brady
'02 Blue Bird, Wanderlodge, LXi, NC

Bob,
Thank you for sharing your experience with us.  I enjoy reading your posts on other subjects as well and feel we are fortunate to have someone on the forum like yourself.  I spoke with an owner of an identical coach to mine who was the original owner and told me he tested the heck out of it during the first year (while under warranty) to make sure there were no overheating issues.  He told me of the same experience you talk about and he had owned the coach for 10 years when I talked to him back in 2001 and there was no apparent damage to the engine. 

Even so I couldn't help but be worried when I saw my engine temperature go to 215 and I would slow way down or pull over.  It's hard to ignore the advice of the manufacture especially when it's such a costly repair.  I added a water system and a digital temperature gauge that would turn the water on at a programable set point but was still not satisfied with it as a long term solution.  Five years ago I added a side radiator (in addition to the OEM rear radiator) with electric fans that did the trick - just 2 weeks ago, the engine reached 212 F on a mountain grade in So. Cal. with outside temp at 102 F.  The other thing I think about is how the inner walls of the engine cooling passageways are probably not conducting heat as well as they were when new - some 21 years ago.

The only way I can reconcile the difference between your experience and the published data is the published limits may reflect business decisions as well as practical ones and the real world is full of shades of gray.  I have to say I think I will feel  a little more at ease when I see those high temperatures after reading your posts knowing there is probably more margin there that what I believed before.

Kent,
In my coach book there's a manual "Series 92 Field Maintenance Recommendations" booklet (published by DD) that has temperature charts for 12 configurations of cooling systems.  Every one has "MAX. TEMP" at 210 F and "ALARM" at 215 F.  It also shows that a 180 F thermostat will start opening at 180 F and be fully opened at 197 F.  It also shows most "modulating" fans "start" at 190 F and are "full" at 202 F

Bob,

When I bought my coach in 2006, I talked to Bruce Mallinson at Pittsburgh Power about turning up the M11.  He discouraged me, saying he didn't know anyone pushing that engine.  Of course, he is building drag racing trucks using N14's etc.

The way these things are designed is that there's a max temp for the coolant entering the radiator top tank. This temperature is related to the the heat transfer across the upper cylinder liner required to stay below the oil flash point as described earlier.

Then there's the maximum outside air temperature at which the coolant system can still maintain the maximum upper tank temp. Of course, there's some reserve built into the coolant system to compensate for scaling and other environmental degradation.

The usual condition is a coolant system that's able to maintain the max upper tank temp within the ambient temperature. Once you go outside the ambient temperature capability, then you're no longer operating within the design of the coolant system. Your in an open loop condition.

Given the coolant systems reserve capacity and given the margin built in to the upper inner cylinder liner temps there's a safety factor designed in, but when you're running at temps that exceed the ambient capability of your coolant system, then the coolant system top tank and cylinder liners will track ambient conditions as Bob pointed out. At some point the lack of lubricating oil at the top ring and the lack of oil heat sinking at your main and connecting rod bearings will result in thermal runaway and your temps will no longer be stable. The trouble is recognizing this condition.

In addition to this there's exhaust gas temperatures and oil temperatures to consider.

Here's an idea, change your oil and do 10 climbs up 17 mile Baker grade in California in the summertime flat out, then have an oil sample analyzed. I'd be looking for a marked increase in wear metals.

It's fun colorful reading, but it isn't science.

David Brady
'02 Blue Bird, Wanderlodge LXi, NC