Engine Overheat?

[JourneytoRet]

Took the RV to Gulf Shores this past weekend cause my kids wanted to ocean fish. Towed my car down and I remember thinking "this engine never seems to get hot". Spoke too soon, on the way back, and if you know I65, it's not a mountainous road by any means, the engine temp hit HOT and tripped the buzzer startling the daylights out of me. As I slowed down to pull to the side, the temp ran back to just below midpoint (letter N in the word NORMAL). Checked radiator fluid level and it was right in the sweet spot. As I drove on, temp would move from N to about L back and forth. Didn't seem related to speed and the needle was fairly active.

In my gas engine truck I would:
1. change radiator fluid
2. check lower hose on radiator to see if it was spongy/soft
3. change thermostat
4. replace water heater

But do not have any diesel engine experience; what do you guys say or think please?

[israndy]

Wow that sucks. I had that same scare recently and it was the top hose. $650!

If you are still going then you are not in the same spot as I was. I would suggest you add your model to your signature so we know what kind of engine we are talking about. Click on the User CP and edit signature.

-Randy

[JourneytoRet]

Updated my signature, thanks.

What was the exact problem with your top hose israndy? Seems like you're going through a rash of problems too. I have signed up with Coachnet RV travel protection and so far they've been great.

[HowieE]

If fluids are good the first thing to check is did the clutch fan come on? Hard to tell on a diesel with it being in the back but if it did you should have seen a real drop on the gauge in a short time.

Have the thermostat checked if you can't do that yourself. Remove it and put it in water on the stove. It should fully open before the water boils.

Do you have an exhaust gas temperature gauge? If so watch it and reduce a gear if it is hold above 1200 degrees for some time.

It may be time to have the radiator rodded and cleaned.

[DaKarch]

Diesel and gas cooling are about the same. Some oil burners have an electric fan clutch so you look for a loose or bare wire check continuity etc.

But what you have described has happened to me personally and has always been the thermostat. I did see a collapsed hose on a friend's motor once.

Start at #3 on your list and work out from there. Look for leaks around the water pump too.

[israndy]

Originally Posted by JourneytoRet

Updated my signature, thanks.

What was the exact problem with your top hose israndy? Seems like you're going through a rash of problems too. I have signed up with Coachnet RV travel protection and so far they've been great.

I would have suggested putting the model of RV you have in there.

On mine it was a blown hose to the top of the radiator. Yesterday I had to put other top hoses on. So I am well over $1000 but not surprising as I purchased a beater RV that has been sitting for 10 years. The repair shop refused to put the mileage as they didn't believe I only had 8k on the ticker. I believe I looked into coach net and it seemed very expensive but I'll look again

-Randy

[JourneytoRet]

Found a Cat dealer just down the road from us. Parts said there's actually two (2) thermostats for this engine! Never heard such a thing before, but will find out this weekend, wish me luck.

[HowieE]

GM uses dual thermostats on there diesels.

[P21932]

My 396XL blew a water pump...hard to get to...while they were in there I had all the hoses changed, the serpentine belt (it was starting to look old) thermostats (yes there are 2) and I had them steam clean the rad and Charge Air Cooler. Not cheap...but less expensive than getting in there more than once.

[J. Morgan]

I have seen impellers spin (come loose) on the water pump shafts on Cat engines with similar symptoms.

It is difficult to diagnose.

My other experience with Cat engines is that they are great, but are VERY SENSITIVE regarding overheating.


Brevi tempore!

[PSchw]

As this is my first experience with large vehicle including cat diesel I got worried looking at me 2 temp gauges and both engine and transmission staying on cold in the rain. If it is not raining they are both between cold and normal so never even saw it going up to normal not even in 100 degree heat.
Peter

[J. Morgan]

These engines should run in the normal range, but I would rather have an engine run cool as run hot.

Assuming the gauge is correct, a cold running diesel can encounter accelerated piston ring and cylinder wear and foul the oil with unburned diesel that washes the cylinder walls.




Brevi tempore!

[israndy]

Originally Posted by PSchw

cat diesel ... 2 temp gauges ... are both between cold and normal so never even saw it going up to normal not even in 100 degree heat.
Peter

Wow, I have seen mine go well over normal. Climbing mountains especially. Of course I have had both my radiator hose and now my Air Chiller hose fail. Got really warm when they were failing but they have since been replaced, perhaps now I will not see this issue. But I have now been trained not to climb a hill without an eye to the temp gauge. If it starts to climb I downshift to keep the engine above 2000 RPM.

-Randy

[ShinyPete]

Journey-

You may want to add a thorough cleaning of the Radiator/Charge Air Cooler "stack" to your maintenance/troubleshooting list. Most chassis mfg's mount the engine coolant radiator and the turbo intake air radiator (CAC) and sometimes even oil coolers together in a "stack" with spacers between. I think your XC may be a Freightliner Chassis with a Cat C7 engine and a rear-mounted radiator? Most big diesels will drip/mist/leak a bit of oil running down the road, and that along with years and miles and road dirt can literally plug up a "stack" causing overheating from nothing more than poor airflow through the stack.

You will want a free afternoon, a gallon of Simple Green or similar metal safe cleaner concentrate, a lot of water, and old clothes. Use a pump up sprayer with a pretty heavy mix of Simple Green and LOW pressure water hose. Wet the stack thoroughly from all possible angles, spray with the mix and let it set. Then flush/rinse with a LOT of water towards the engine as much as possible as that is how it got dirty. Then do it again like 2 more times. Don't use a pressure washer or a brush as you can damage the radiator fins. You might be amazed at how much crud comes out. I did it at least once a year when we owned a Spartan side stack chassis and I was always shocked at how dirty they got.

Hope this helps!

[Ron_Kat]

I agree with Shinypete I flushed the exterior of my 35xc last year , I was amazed at how much crap and how long it took to have clean water come off the radiator. The cooling fan combined with rear tires kicking up road dust mist ect... really fouls the cooling fins not allowing heat to dissipate.

[JourneytoRet]

Well, over Christmas break me and my 11 year old daughter (she is a tremendous help!) tackled changing the two thermostats. After I described it, and how it works, she was quick to pick it out on the Driver top side of the Cat. 6 bolts removed and a rubber hose clamp later, voila, easy to change and replace.

I did demonstrate to her on the stove how the old ones should work. One opened/closed reliably around 180 deg F, but the other one was a bit sketchy. Also took 2 gallons of antifreeze to replace what splashed out.

Next weekend, we purple power the radiator from the fan side and then gently hose it from the outside in, making sure we put in a temporary shower curtain to protect the Cat from the water and debris.

What have we forgotten?

[PSchw]

Just learned at the Freightliner Camp of a modification which keeps the radiator cleaner.
Draft-tube extension.

Extend blow out tube be one the radiator.
There are also different oil pans on the engines with different oil capacities which can lead to overfill and blow the oil right in your radiator. This was what happened to me.

Peter

[KenandjeanF]

1999 Cutter 35' 3126 Cat 88,000 miles. Purchased 2 years ago from first owner in Long Beach, kept running hot in Arizona where we live 100-110 degrees, finally had radiator removed and cleaned but not rodded out, replaced both thermostats, all new hoses, replaced water pump belt and still runs hot on really hot days. Then read 18 years of repairs and found that it always had a heating problem on hills and hot weather. Owner said he just ignored the heat gauges. Buzzer and warning light comes on at 220 on the transmission heat gauge or needle to the right on the engine gauge. Don't tow anything and run 60 mph so will just live with it.

Originally Posted by JourneytoRet

Took the RV to Gulf Shores this past weekend cause my kids wanted to ocean fish. Towed my car down and I remember thinking "this engine never seems to get hot". Spoke too soon, on the way back, and if you know I65, it's not a mountainous road by any means, the engine temp hit HOT and tripped the buzzer startling the daylights out of me. As I slowed down to pull to the side, the temp ran back to just below midpoint (letter N in the word NORMAL). Checked radiator fluid level and it was right in the sweet spot. As I drove on, temp would move from N to about L back and forth. Didn't seem related to speed and the needle was fairly active.

In my gas engine truck I would:
1. change radiator fluid
2. check lower hose on radiator to see if it was spongy/soft
3. change thermostat
4. replace water heater

But do not have any diesel engine experience; what do you guys say or think please?

[JourneytoRet]

After tackling the oil/filter change, which was ridiculously easy (and makes me wonder if I missed something), am moving to the coolant change today.

Armed with gallons of distilled water, ECL and a couple of bottles, I plan to:

1. Drain
2. Fill with tap water and 2 bottles of flush (will check to see if I need to bleed at thermostat housing on my Cat 3126)
3. Run engine til hot (how long should i run. Prestone flush says for heavy cleaning i should drive 3-6 hours over a few days?!)
4. Stop engine and let cool
5. Drain
6. Fill with distilled water
7. Run engine til hot
8. Stop engine and let cool
9. Drain
10. Fill with 50/50 ECL & distilled water
11. Run engine til hot
12. Make sure temp stays steady
13. Check for leaks
14. Check overflow level

What else am I missing?

[GCinSC2]

I've become very attached to using my IR temp gun to search and trouble shoot cooling systems.

If you have access you can point and shoot and watch temps at various points.

I was sold on it years ago when I watched a tech pinpoint a t stat issue on an old 7.3L company truck when I was on the road with a cold engine.