Cat 303CR Overheating

[billyo]

Hi everyone. I have a 2005 Cat 303CR open cab mini with around 4500 hours. Bought the machine a couple years ago with a cracked cylinder head. Had brand new head from Cat installed right after purchase. Machine runs and works great. However, it would occasionally overheat after a couple hours of work. This has gotten progressively worse, so now after about 20 minutes it boils over. Replaced thermostat with new Cat unit, with no difference. Left stat out, no change. Alternator/water pump belt is tight. I can let it sit and run for hours, and temp is fine. But 20 minutes of very light digging and water is boiling out of the overflow tank. Cooling fins in radiator appear clean (can easily see through them), and I've sprayed cleaner & hosed them out anyway a couple of times. No water in oil, and no coolant leaks. I'm suspecting perhaps a water pump with missing fins or a spinning impeller. (I can remove cap and fill with coolant, and when I start engine, level does not change at all). Is this something that seems to happen on these S3L2 engines? Any suggestions? I only use the machine for generally light work on my property and love how it works, but this overheating is getting old...

Thanks in advance!

 

[Delmer]

Anything is possible, get a non contact infrared thermometer and take some temperatures of the top and bottom of the radiator when it's overheated. That will narrow it down.

 

[CM1995]

Welcome to the Forums billyo!:drinkup

Is the hydraulic oil cooler and radiator sandwiched together? I've run into overheating problems before where the radiator and oil cooler were sandwiched together and both look clean from the outside but are filled with gunk between them. The oil heats up during use and the heat has no where to go right next to the radiator.

 

[billyo]

I just topped off the coolant and started it up. I'll shoot temps after it's run for a while.

Regarding the placement of the oil cooler, it is sitting in front of the radiator with about 1 1/2" of open space between them and there's no obvious garbage caught in there.

One thing I have a bad habit of doing that may contribute to the problem is running the machine at half-throttle. Perhaps running it at full throttle would increase both coolant and airflow enough to stop overheating? (Of course at full throttle would also make more heat I suppose...) Any experienced opinions on this?

 

[billyo]

It just seemed strange to me that the coolant level did not change at all at the filler neck when I started and revved engine (tstat still removed)

 

[Nige]

I think if I was you I would have the complete cooling package out of the machine, split the hydraulic oil cooler from the radiator, and throughly clean both of them. With everything installed in the machine this is next to impossible, and even if you can see right through the fins in some places there could well be contamination in there somewhere. The modern designs of excavator have the cooling package running so much on the edge that it doesn't take much in the way of air flow blockage to tip them over into an overheating situation.

As someone suggested, shoot the temps of the top hose and the bottom hose when it's overheating and post the results.

 

[billyo]

Well, I learned one thing this evening - I need a new IR thermometer! Temp outside is around 80, but according to mine, it's 50, but later it's 60, and sometimes 142..... And I'm obviously dead, as it says my body is 72 degrees. But anyway, I checked top & bottom hoses at various times and there was always a 10 degree difference between top and bottom. I'll get a new temp gun tomorrow and get solid numbers.

Overflow bottle is bothering me though. Was running at full line while idling. Shoved some dirt around for a few minutes, and it was near top. Idled for a few, and it abruptly dropped below low mark. Added about a pint. Worked it a little more, and it again went near filler cap. Idled for 5 minutes, and back below full mark. When it cools down after shutting it down, I expect it will be near empty. I know that's what the overflow bottle is there for, but at least a pint of water just disappeared in about 10 minutes. No bubbles in tank, no water in oil, but sure sounding like a head gasket.

 

[Delmer]

With 10 degrees I'd say the water pump is probably fine. The radiator plugged is the first and still the most likely suspect. Or it could be poor circulation from a weak water pump/bypassing from missing thermostat, and a plugged radiator and show the same low temp drop across the radiator.

You do have a thermostat in there now, right?

You have to shoot the same spot to get consistent results with a temp gun. The hoses work, or the top and bottom tank as long as they're not shiny metal. Shiny metal doesn't read right with a temp gun.

 

[billyo]

Thermostat is still out. Was still overheating with original stat, new stat, and no stat. Really seemed to make no difference.

One thing I have not changed is the actual radiator cap. It has one on the upper hose for filling the system. The other is apparently gonna require disassembling the entire machine to change. (I can get it loose, but there's not enough clearance above it to lift it enough to remove it...) The overflow tube from the radiator cap connects with a tee to the overflow from the cap on the hose, and then runs to the overflow bottle.

The missing water still concerns me though. If it's not going into the oil or on the ground, would have to be burning it.

I think I'd still rather replace the head gasket on this thing than remove the radiator, though! They must have set the radiator in place and then poured the excavator around it.

 

[Delmer]

Thermostat is still out. Was still overheating with original stat, new stat, and no stat. Really seemed to make no difference.

If it makes no difference, put it back to original and try something else to find the problem. It really shouldn't need any radiator cap to keep from overheating in 20 minutes, same with the loss of coolant. That's not enough to worry me one bit, there's plenty of backyard machines that run around for years with half empty cooling systems, and do just fine. The water loss and unchanged original thermostat are serious long term, but they're not your problem now. If the engine as it cools sucks the water out of the overflow bottle, but not all of it so that it gets air, and you can verify that by the radiator cap having coolant right up near the top when cold, then don't worry about it for now.

 

[Clguest]

Delmer's comment about plugged radiator is a feasible scenario. Similarly, any restricted or plugged passage in the engine cooling water flow could allow the water to boil in that section of the block or head. This would quickly change the water level in the radiator due to the steam expansion. For an engine with 4,500 hours, this is a possible scenario and one that seems to fit the symptoms you shared. Drain and flush the system throughly if this has not already been done. If it began right after the new head was installed, it is also possible that the gasket is misplaced and restricting flow.

 

[billyo]

All excellent thoughts, guys. I can only assume it was overheating prior to replacing the head, hence the cracked head. Hadn't really thought about "hot spots" creating steam and blowing out coolant, but makes sense. Gonna run some flush in the system for a while and clean the exterior of the radiator & oil cooler and see what happens. Any opinions on best radiator flush? (I know I should remove radiator & take to shop, but that's no easy task on this machine - figure flushing is worth a shot)

 

[Nige]

Your 10 degrees difference between top and bottom hose temps is really not enough. For a radiator in good condition it should be a minimum of 15 and preferably nearer to 20.

 

[Delmer]

Sorry, I was talking about the radiator plugged with dirt on the outside, like other's suggested. If the radiator was moving enough air, but was plugged on the water side, I'd expect the temperature difference to be much greater than 10 degrees.

What was the coolant like when the head was replaced? and what does it look like now? That's low on my list of possibilities, dishwasher detergent is a good radiator flush for oily gunk and grime, (for a machine, not dawn, cascade etc.). If it's had hard water added to the radiator then an acid is needed to remove the deposits, but I wouldn't do that without solid proof that you have hard water deposits. A couple flushes with rain water is a good way to see what comes out, it will turn a little rusty colored normally, but anything that settles out in the bottom of the bucket you drain it into is telling you something.

Have you checked a manual to see that all of the foam and air flow parts are in place? Any exhaust leaks? I wouldn't think half throttle would make it overheat by itself, but running it 3/4 would make it even less likely.

 

[billyo]

OK. Now I have more to go on. Put some radiator flush in and topped off with water. While it was running, removed all the guards in front of the radiator & oil cooler. At high idle, about 160 on top hose, 150 on bottom. (Amazing how much better a temp gun works without a battery that expired 3 years ago...) Feels like very good airflow through radiator. Folded oil cooler back out of the way, and radiator looks good though a little dirty. But, the entire left side of the radiator is cold, from top to bottom. Right side is warm. Middle will make you curse when you touch it it's so hot. So now, I'm thinking either some serious plugging up inside the radiator, or I'm back to weak water pump. Sprayed all the tubes & fins down with some cleaner and letting them soak. Gonna go backflush inside of system with a water hose and wash out the outside.

Regarding the condition prior to replacing the head, I still have the old head and it looks very clean inside. Looked at block while head was off, and coolant looked clean.

 

[Delmer]

Is 150 and 160 while it's overheating???

 

[billyo]

No, Delmer. It actually only boils over after being under load for a while. I just shot those temps after it had run at a fast idle for an hour or so.

I'm thinking I've found the problem though. After running with flush for an hour, drained it and backflushed into a bucket with water hose. Didn't get much (teaspoon or so of crud). Refilled and added flush again and let it run. Now, in addition to a few tubes near the middle, 3 on the right side get hot. At least half of the face of the radiator is actually cold while running. I would expect the tubes farthest from the upper hose inlet to be cold if it were weak flow, but it's actually all the tubes directly underneath the inlet (and right above the outlet) that are completely cold. So, I'm thinking it's a clogged up (internally) radiator. There's enough tubes open to keep the engine cool unloaded, but it can't handle the added heat when it's digging. Looks like I might as well pull it over out of the way and start disassembling it to get the radiator out to take to be rodded out. I guess that how hard it is to remove has absolutely nothing to do with whether it's bad or not!!!

 

[Delmer]

I won't argue with taking it out, but to me that would be to clean the air side. To flush, I remove the lower radiator hose and the cap, stick a garden hose in the cap and an air nozzle in the bottom with rag around it, when the radiator overflows give it a shot of air, let it refill and repeat. Don't seal it too tight or use too big of a nozzle or the radiator might burst. Use rain water for the flushes when you run it or you're just adding more mineral with each tank of new water.

A teaspoon in a little radiator like that is plenty of crud. Was it mineral or gunk? How much swamp water has been added in the time you've had it?

 

[billyo]

Well, just finished getting it out. 4 1/2 hours and contrary to what Cat says you do not need to remove the counterweight. (Probably would have been easier to just remove the counterweight!!!!) Anyway, the tubes I can see from the filler neck have big flakes - some 1/2" size - sticking out of them, or are 1/2 plugged or more. And these are the ones in the center that had some flow. I don't think any amount of flushing would get this stuff out. To answer Delmer's questions above, what came out when I flushed it had a little rust, but mostly looked like cat litter. And since I got the machine after replacing the head, I always just used the 50/50 premix green coolant. But when the issue progressed to the point that it was boiling over every time I used it, I am guilty as charged for using the water hose!!!

I suspect this is the rest of the story: It was a rental machine, and from what I've read, these 303's are prone to overheating in very hot weather. Someone's rented it, overheated it, filled it up while hot and cracked the head, and it probably had quite a few doses of various stop leak products added over time which ultimately clogged the radiator.

Still pondering where to go from here. Radiator was not what I expected - aluminum 2-core with plastic tanks, just like a typical automotive unit. Size wise, it sure does look a lot like the big thick brass / copper radiator in my old Jeep CJ. I have a welder and a well-equipped machine shop - I may just get creative.

Thanks so much guys for the help. Your advice got me thinking and actually checking things.

 

[billyo]

FYI: I have a "racing style" all aluminum radiator on the way. Plan to install it in a way that it can be removed wthout disassembling half of the machine. While it's out and everything's opened up, going to upgrade the alternator mount to something more solid. Gonna try this first with an electric fan system. If anyone is interested, I'll follow up with results.