D8K running hot

Paul - The D8K's were notorious for running hot in our climate in Summer. Their cooling systems ARE marginal. There's not much you can do, except clean and flush the cooling system, wash out the radiator core using a small portable firefighter, and a tank containing some washing powder (to clean out greasy deposits), and check that radiator fins aren't bent over or sandblasted.

The engines are running at their maximum output, at the end of their design life .. and they suffer from cracked heads and overheating on a regular basis.
You might want to treat the cooling systems with a de-scaler to remove any scale buildup (common with most of our water, unless someone has used pure water or factory coolant) to assist with optimising cooling. There is also an additive you can buy and add to coolant, that reduces operating temperatures.

The engine and transmission oil coolers are also a problem area if scale or rust is present .. and often, they need to be removed, or even replaced, if the tubes are badly clogged. Also, check the condition of your fan pulleys, to ensure they aren't badly worn, and allowing belt slippage.
The last thing to do is to ensure that the rubber strips around the radiator core are in place, and haven't been thrown away or left out. These strips are critical to ensuring that the hot air doesn't recirculate around the core, thus reducing the fans effectiveness.

Having run D8k's in heavy work [Srub Pulling and Bladeploughing ] for ten's of thousands of hours Radiators and Fans are the most important thing. What type of Fan are you running [Reversable , blower ,sucker or trash cutter] and what type of Radiator do you have. Many W.A. machines were fitted with Massabi [?] cores which worked fine if you only had dusty conditions, but were hopeless if you had any trash or fluffy stuff floating around. By far your best is to fit a Coarse Core and a Trash cutter Fan. Are your units just hot or are they Boiling over? Daily blowing down is normal Maintinance when in dirty work . You wouldn't expect 2 machines to be giving same problem but I have had Thermostats lock up. and there are other things. An infra red heat gun is a great unit for picking up hot spots, I have picked up many problems in Cat and Cummins with these units. As Oz Dozer says D8k's 342 Motors are streched to the limit , But with good Maininance. they will do thousands of hours. Their main problems are a weak Jockey Pulley set up [Can Modify] Cracked exhaust Manifolds, [ Ganasi manifolds are far better that Cat [but use Cat seal rings] . Water cooled turbos are much better than the earlier non cooled ones. Spacer plate motors are less troublesome. if Djcat comes online he may help you ,he's one of the Best D8 trouble shooters in the country. All the Best .

I agree with all the comments above.

One thing I might add in the US we had a landfill radiator core that had an extra row of tubes also had another lower crankshaft pulley that was bigger and gave the fan more RPM's.

The other option was turbo aftercooler and lower fuel setting. Thats the best we could do to keep them cool. Tim

Paul - Lance has added a lot of additional info that I missed. These old Cats often have a sandblast grid mounted on the inside of the core, too .. and these can add to cooling problems. Fine trash gets caught between the grid and the core and slows down airflow.

Lance is right, a coarse finned core, is generally more effective than the standard fine-finned ones. Cat kept adding fins to radiators, over the years, and kept telling us that more fins = better cooling (more surface area).
In theory, this is fine .. but in practice, with our native and imported grasses producing fine fluff (which is picked up by the blower fans off the tracks), and with it getting pelted into these fine-finned cores .. they are a real PIA, and they block up quickly, and reduce air flow substantially. As a contractor friend used to say .. "you can read a newspaper through the old Cat cores!!"..

In addition, Cat produced copper, brass and steel cores. You could get all-copper cores, copper fins with brass tubes, or all steel cores. This was to try and overcome sandblasting problems. The all copper cores have the best heat-transfer properties, but the brass/copper and steel cores have better sandblast resistance, in that order.

The Mesabi cores were offered as a repair advantage, and with more resistance to cracking from vibration. Tube cracking on Cat dozers, was never a problem, in my experience (unlike locos, which is where the Mesabi idea came from) .. but the Mesabis were handy when you poked a log through the core, and you could just replace a few of the individual tubes.
However, the Mesabis offered no cooling advantage, and they were/are, very pricey. I have seen very few Cats converted to Mesabi cores.

My recommendation is to rip out any sandblast grids, and install perforated engine side covers. These do a better job of keeping trash away from the fan and radiator, and if properly-perforated, don't reduce air-flow. If you need to replace any cores, buy a core with good fin clearance, and with copper fins, if possible.

Well Paul looks like there are plenty of good ideas there for you to stew through.

Heres some more...

Check that the belly gaurds are fairly clean. Dirt is a good insulator and will hold the heat around the engine and tranny compartments.
Reseal the pressure valve on top of the radiator if it looks a little suspect.

Check the brake adjustments and be sure they are not dragging causing the engine to work uneccessarily.

A supplemental cooling system group was offered by cat to over come heating problems in trashy work....They replaced the radiator ( 7 fins per inch ),c/shaft pulley and fan ( GR #8n7042 ) They used a trash cutter fan as Lance mensioned.
If you are running a reversable fan then I would look seriously at replacing it with a solid fan. The reversable blades wear and loose their pitch which reduces wind flow. Also I have seen blades come off and go through the radiator. D8L fans can be fitted ( p/n 2W5082 ) if D8K ones aren't available (p/n 4W8409 trash cutter or 1W0546 std ). Wind speed should be around 5-600 fpm at the outside ( ie blade tips ) at idle.
As Lance mentioned an infrared heat gun would be a worthy investment for ironing out heating problems. The heat drop across the radiator should be around 8-15 deg and across the coolers about 15-40deg F . Depending on what the results are you could have internal or external conditions to deal with.

If aftercoolers were fitted at a later stage the rack setting must be changed to prevent overfueling and hence may cause over heating and worse still dropped valves or head cracking. Be sure the water flow through the cooler lines is ok. I have come across water lines being blocked by a poorly made gkts that never had the hole cut through the centre to allow water to pass through it!

Fuel timming could be worth a check . The D8K uses a 5P4240 fixture plate which sets the timming at around 14.2 deg btdc. The D8H with the same compact fuel system runs at just over 16 deg btdc at only 270hp and uses a different fixture plate.

Tranny slippage or a poor torque convertor can bring the water temp up which will bring the engine temp up with it. Does the tranny temp come up first thus bringing the engine temp up? If the t/c is sad it will have more internal leakage that it otherwise should and the scavenge pump might not be able to get the oil out from the t/c compartment and hence the t/c "floods" and the extra oil is thrashed around causing it to heat up.

Injector nozzles might be worth checking for proper function, be sure the right ones are fitted for that engine I have seen nozzles fitted with the wrong p/n. ( which looked the same but were for another application )

Something of note.... the older style temp gauge ( 1W5170 ) seem to read different to the new updated gauge. The newer gauge reads higher quicker than the older style. It can give the perception that the tractor is over heating. I had this happen once and managed to get a new older style gauge and it went just fine. This was also checked using a thermister Group while the tractor was at operating temp just to prove the gauge reading differences.

If all else fails .. just work night shift..LOL

Well that should just about be enough to give you a head ace... good luck.

Cheers djcat