I got a problem thats got me thinking ( overthinking) maybe? Its a newly acquired Caterpillar side boom. Its essentially a D8R or at least Was a D8R, its now converted to a pipe layer. S/N 7XM02554. It has a turbocharged 3406 engine in it and it keeps pushing coolant out of the over flow hose. The machine was around 8L low on coolant when I first had a look over it. So right away assumed possibly head gasket. BUT it does not test for combustion gases when its bubbling and pushing coolant up. It also does not seem to be building pressure if you put a pressure gauge on the rad neck. So I put the over flow hose into a pop bottle and it pushed a bunch of coolant into the bottle, then with the hose submerged its blows bubbles like crazy. However not all the time. Seems to do it worse once engine is warmed up and less if you let the coolant temp drop down. Ie: low idle at -15C. If you ramp it up to full RPM no load for a while after around a minute or two it sometimes starts bubbling like nuts, but not consistently. If I torque stall it and load up the engine it does not seem to affect the bubbling or have any correlation to wether it bubbles or doesn’t. At one point it was sitting idle for awhile and I noticed the majority of the coolant in my pop bottle over flow had been sucked back in the engine, as the hose was submerged in the fluid. The engine runs good, no white smoke, charge air is bone dry on the air side, not a liquid cooled turbo, . Im confused. Im thinking Im gonna start by going after/ inspecting the water pump and T -stats. It doesn’t have any over heating issues, seems to settle out in/around 80C engine temp when running it around. Any suggestions? Thanks for any advice you may have.
Get hold of a radiator pressurising pump and put some pressure on the cooling system when it’s up to operating temperature. That may help you find if the source of the leak is internal or external. Check whether the water pump weep hole is blocked also.
Nige, would it do any good to first pressurize the cooling system when cold and look for leaks? Since he's not developing pressure when he puts a gauge on it, I wonder if he's sucking air into a leak somewhere? I've seen this before with fuel systems on older Cummins where a leak before the lift pump causes lots of bubbles under suction but when just sitting there, the system had no leaks. Only pressurizing the fuel tank would show the leaks. I don't have a layout of his cooling system so I figured you might know a potential source of leaks under suction. I'm thinking like a lower radiator hose or equivalent that feeds the water pump. If the radiator has restriction in coolant flow, he might have a good suction on it when the thermostat finally opens up and allows full flow. This is consistent with his observation more bubbles when hot, less when cold.
No harm in it at all. Pressurizing the system both cold and hot may reveal something.
Yess sir, I definitely agree. We did already pressure up the rad cold and didn’t see any obvious leaks. I think it’s something going on with coolant flow. Either a blockage or something causing the coolant to push back up into tank instead of from the tank to the water pump inlet. I have seen a bad water pump ( incorrectly assembled) have too much impeller clearance and cause weird issues, but that came with over heating problems.
So it's not overheating at all.? That wasn't clear from your first post. TBH maybe a bit of a look inside the water temp regulator housing might give you a clue as to whether the system is anything like clean inside. Maybe all it needs is a good flush.?
At that temp the regulator should be only just opening. It won't be fully open until about 92 Deg. I wonder if it has the correct regulator in it or maybe the regulato is stuck open.?
While in it, you might think to do a redneck radiator flow test. With the top and bottom of the radiator unhooked, pour a bucket of water in on the top and see how fast it flows out the bottom.
Does it have a jacketed aftercooler? or a added air compressor?
It has an aftercooler like any other 3406 Ive seen, the housing right on the engine, with the liquid core inside of it. It is bone dry inside ( looking with a borescope) no signs of coolant in it. It does not have an air compressor on it.
A bit of an update, the thermostat for main jacket water isn’t working properly. It does open in hot water but not fully and not until around 94C. At 83C (180F) it does not open at all. When i took the sender out and tested it, it does seem to be fairly accurate. The gauge on the dash reads what my temperature probe is showing. Again using hot water with a thermocouple read out to monitor the waters temperature. So, the water temperature regulator not working. Water temperature gauge is working. At no point did the water temperature gauge show the engine being too hot while I had the machine running. SOOO, im thinking if the Stat wasn’t opening is there anyway the coolant could have been boiling causing my bubbles while simultaneously Not showing High coolant temperature on the dash?
248-5513 Caltherm Water temperature regulator is whats in the machine. Supposedly a 180F unit. It seems to be somewhat chewed up/scored where the seal sits and it slides past when it opens and closes. Definitely will be putting in a new one. In my mind I cant see how it could be stuck/ not opening and cause the coolant to boil, but NOT cause the water temperature gauge to show high temperature. The water temperature sender is in the head just before the water temperature regulator. So if the coolant was getting hot, the sender should definitely sense it.
Heres another thing Ive never seen. This is a picture I took with my borescope of the face of the oil cooler right off the water pump discharge. Never seen one looking like this. However the tubes don’t appear to be clogged. I will likely still open that up to check and or clean it. At the very least get that weird piece out of there. It literally looks like someone siliconed around each and every tube?? Or some coolers just like this?? I’ve mostly used Genuine cat before, so not sure if this is Normal with some aftermarket stuff? Not entirely sure what this metal piece is. Kinda looks like a Valve keeper.
Stats that open suddenly {is not uncommon, which is what yours is doing}, still not correct. That oil cooler--I've never seen one like that, oem or aftermarket. Three main areas that cause air in cooling systems, pump cavitation, compression entering cooling system, air charge cooling. The reason I brought up aftercooler is on one rare occasion a Cummins aftercooler showed no signs of leaking coolant but 30 psi boost was entering system, only under a constant hard throttle. Also have had bad bottle tests checking for gases. On ones that were hard to troubleshoot I ran a sealed cap with long hose and gauge into cab to watch under a load condition. And a story to go with it, one of our Series 60's had a issue like yours {it was under warranty} so sent it to dealer, they came back with {nothing wrong internally}. Gayle my cohort in shop went to go get it {I sent him with my gauge setup}. It made it two miles from dealer turned around went back to service desk, had the service manager ride with him with gauge hooked to tank. Back in the shop it went, #5 liner ever so slightly below PH, the area was miniscule, needed heat/psi to leak. Leave plenty of expansion room in top rad tank when testing. Also use a inferred temp gun in all the areas of cylinder head, stat housing, top hose. * One final question, does this system have a shunt line from stat housing to top radiator tank to release air in system, if it does is hose open?
Im gonna have to do more digging on this issue for sure. There is a shunt line from pipe just after the stat housing up to the tank. I will have to check if its open or not. We sort of did your sealed bottle test, by attaching a cooling system pressure tester onto the rad neck, basically using the tester to act as our gauge set up, never seen it build pressure though. Gonna have a closer look at the oil coolers too. If flow was blocked up could be causing issues. There is two of them in series essentially, engine oil ( the one I have pictures of) and then right after it, transmission oil, then into the engine block and eventually up to the stat housing where it goes to the rad or bypass line. It has a bit different of a radiator on it tho, only a bottom tank and then a bunch of vertical cores with little bleed hoses attached to the top linking them all together. The “top tank” is really just an expansion tank with a 1” hose to water pump inlet for head pressure and obviously to connect it to the cooling system. I gotta do some looking into that, as im not 100% familiar with how flow is thru it. Possibly some blockage issues in there too.
I’m guessing that cooler is aftermarket.?
That’s known as an AMOCS radiator. If you search on the forum you should find illustrations of the bottom tank. It is not unknown for the weld between the baffle and one of the pipes to crack and significantly reduce the flow through the radiator because coolant simply goes straight from the inlet to the outlet without passing through the cores. HeavyEquipmentForums
Im not sure. If its actually built like that then I would have to assume its not genuine cat.
Yeah, I guess from the bit I checked into it, its supposed to be so that each core is easier to replace and service versus having to replace the entire radiator. But again you would think if the radiator wasn’t doing its job properly then the engine temperature rise would continue to increase until it overheated i will definitely have to be doing some more diag on this machine. So far I don’t think theres any smoking gun. I will be back at it monday and hopefully continue digging into it. ( assuming some other catastrophe does come before then)
Can you find any part numbers on the outside, or maybe a Cat logo (or not as the case may be) cast into the body.?
Cummins had the low flow cooling systems that did the same basic thing as AMOSC, but when that baffle had issues overheating was certain.
I will look closer at it when Im back at it in the next day or two. Most likely gonna pull it out.