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I have a gray market cat 312b excavator. the hydraulic system…

I have a gray market...
I have a gray market cat 312b excavator. the hydraulic system reaches HOT in 30 to 45 minutes of operation. I shut down or idle until it cools down and then go back to work. filters are new. oil is 400 to 500 hours old. what do I look for?

thx,

Tim
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Answered in 5 minutes by:
8/18/2013
Mechanic: catmastertech, Technician replied 9 years ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,998
Experience: Field service technician for CAT 19 years.
Verified

catmastertech :

Have you replaced the baffle seal under the hood?

catmastertech :

Have you checked the seals around the radiator and oil cooler?

catmastertech :

Are the fan belts new?

catmastertech :

I would not recommend running engine oil 500 hours.

catmastertech :

Hydraulic oil can go up to 4000 hour if it is a high quality oil and is sampled regularly.

Customer:

fan belts are new. engine oil is less than 100 hours. hydraulic oil is 400 to 500 hours old. seals look good. not sure what the baffle seal is...

catmastertech :

You should have a thick foam baffle seal glued to the hood and this will seal the hood to the radiator.

Customer:

hydraulic oil has become cloudy...dirty looking.

catmastertech :

This prevents air flow from the engine bay circulating back into the radiator.

catmastertech :

Cloudy oil indicators contamination, possibly water.

catmastertech :

Foamy oil would be air leaks or no pressure maintained in the tank.

Customer:

this tractor is 13 years old...the baffle seal you mention is probably coming apart due to age...

catmastertech :

Yes it is very common.

catmastertech :

Which way doe the hood open?

catmastertech :

Does it tilt back?

catmastertech :

Or open to the side?

Customer:

door on each side of machine and cover on top that raises for access to engine. I figure the foam I was throwing on the ground was for noise abatement....

catmastertech :

Does the hood tilt open to the back or to the side?

Customer:

I can send you a photo but the doors on the side open horizontally and the cover on top is lifted vertically....

catmastertech :

Yes but does it hinge on the back of the machine or are the hinges to the side?

Customer:

top cover hinges on toward the front of machine

catmastertech :

Ok, I have never seen one open that way. Maybe the seal will be the same and US versions. Try a(NNN) NNN-NNNNliner.

catmastertech :

This may fit close enough to seal the hood to the radiator.

catmastertech :

Use a contact cement on the hood and the liner to glue it to the hood.

catmastertech :

Also inspect the sides of the radiator to see if the seals are on each side.

catmastertech :

Inspect behind the oil cooler and the front of the radiator.

catmastertech :

When clearing fresh land or house debris, this area will plug often.

catmastertech :

After everything else has been inspected and sealed. The last thing to try is converting the machine to High Ambient version.

catmastertech :

The only part of this you can do on the cheap is to add a louver to the side door to allow more fresh air into the radiator.

catmastertech :

I would recommend using a fine screen if you are clearing land to prevent trash getting into the coolers.

catmastertech :

If removing the door helps keep the machine cool, install a louver in the upper half of the door. Do not cut the bottom of the door, this would only suck dirt into the coolers.

catmastertech :

Machines that work in high temperatures should have the High Ambient conversion.

catmastertech :

This includes pulleys, belt, fan and water pump. They are all different.

catmastertech :

The side door and bottom cover are louvered for more air flow.

catmastertech :

About

catmastertech :

$2500 in parts.

catmastertech :

I am assuming you have not modified the fuel system or hydraulic pump and these are functioning normally.

Customer:

no modifications. I just looked at the baffle seal you mentioned...it's in good shape. next to radiator, foam and real tight. the top cover opens to the side...life cover vertically and hinges are on left side of machine...both radiators are in real good condition. clean, like new.

Customer:

i'm thinking there is a pump problem...maybe not getting the circulation that is needed for cooling.

catmastertech :

It is always a possibility. Just as a thermostat and even a radiator cap. (the cap got me once so, i replace them whenever I have a problem)

catmastertech :

If you have a heat gun (infrared thermometer) check the temps on the inlet and out let of the radiator.

Customer:

what is the normal operating temperature range for a 312 hydraulic system? I shot the main pump with a red dot thermomter and read 195 F...thought this to be too high and quit.

catmastertech :

you want to see 5 to 10 degree drop, the closer to 5 degrees the better.

catmastertech :

100 degrees above ambient air temp.

catmastertech :

Is normal operating temp

catmastertech :

Most gauges should be working in the straight up range.

catmastertech :

Too far to the right and the alarm will sound and light will flash.

Customer:

100 above ambient makes sense to me...we got to 85 degrees today. the gauge in the cab runs over to 80 or 90% within 45 minutes of working...i'd rather see the guage at 50 to 60% maximum. just saw your last comment and yes straight up is ok...but let's not go much farther to the right.

catmastertech :

It is ok for short periods but, you are right to not want to see it stay there.

catmastertech :

Does the oil temperature always heat first?

catmastertech :

What type of work are you doing?

Customer:

engine temp never leaves the first bar. cool as a cucumber. the hydraulic temp is what goes high real quick. i'm digging pine stumps...it's hard work. no dust. ground is wet. stumps are deep and tough.

catmastertech :

What does it do for normal work?

Customer:

the same. if boom and stick are moving...it's getting hot.

catmastertech :

You must have a restriction further into the control valve or a sticking pump control.

catmastertech :

Have you had any other problems before this?

Customer:

serial number of machine: 9HR5055

Customer:

no previous problems.

catmastertech :

Check the oil temperature of the oil cooler. It should be about the same as the tank.

catmastertech :

If not, the oil cooler bypass valve may be stuck open.

catmastertech :

You may need to monitor it when starting up to see if heat is building in the valve or some were else.

catmastertech :

This is the block from the main control valve to the oil cooler.

catmastertech :

These are the return flow lines. All flow leaves the valve and will pass through the block and then to the cooler and on to the tank.

catmastertech :

Monitor temp from the valve to the block and then from the block to the cooler and lastly to the tank.

catmastertech :

Sensor is in the tank, the oil in the tank should be close to the gauge.

catmastertech :

Compare the temperature just incase the sensor is wrong.

catmastertech :

I haven't seen this often but, wiring does get corroded and cause bad readings.

catmastertech :

I would also sample the oil, water will make it not cool as it should and could damage the pump.

catmastertech :

If it is foamy, the oil will be clear when the machine has been sitting.

catmastertech :

Also the tank should have pressure on it after it has been running for some time. About 5 to 9 psi.

Customer:

the oil does not look good. if there's water in the oil I would think there would be separation of oil and water and sitting still...but that does not occur.

catmastertech :

When the concentration of water gets to high, it will not separate. Hydraulic oil has additives to help it collect the water and hold it until temps will evaporate it but, it must be small amounts. (normal condensation)

catmastertech :

The most common source for water in hydraulic oil is it being introduced when filling. (using dirty buckets, keeping old bucket exposed the rain)

catmastertech :

No connection in the system to the cooling system.

Customer:

then there is not water in this system.

catmastertech :

I would have it sampled to find what is in the oil. Good oil would be clear and golden in color. Best oil is straight 10W oil.

Customer:

does excess heat damage the oil?

Customer:

oil is straight 10w...

catmastertech :

Multi-weights are ok but, may be too thick in cold weather.

catmastertech :

Yes, high heat will break down the additives and burnt the oil.

Customer:

it is not clear and golden...it is brown and dirty looking.

catmastertech :

OOPS- burn

Customer:

that's what I thought. I

Customer:

i

catmastertech :

Have you changed all the filters recently?

Customer:

I have quit till this prob is solved!4

Customer:

not too long ago...less than 100 hours.

catmastertech :

New oil and filters?

catmastertech :

Did you inspect the old filters? (cut them open and look for debris or metal)

Customer:

if the oil is burned...do I change? and there is 25.8 gals in the tank and 41.4 gals in system...how do I get rid of the difference?

Customer:

no...there did not appear to be anything wrong and there was not a heat problem.

Customer:

no new oil...new filters. the oil was changed back 400 to 500 hours ago.

catmastertech :

Did the heating problem begin right after the filter change?

catmastertech :

The only way to get all the old oil out, is to cycle and change it again.

Customer:

it's hard to say...the machine has done a lot of sitting. this excavator is used on my farm and the use is off and on...probably not a good thing but that the way it is...

Customer:

so dump the tank...use the machine and dump the tank again?

catmastertech :

Your dealer can sample and clean the oil with a Kidney Loop machine that will get the oil super clean. This will reduce the amounts of oil needed to change out.

catmastertech :

Other than Kidney Loop, changing it is the only way short of removing all the cylinders.

catmastertech :

OOPS- changing and cycling

catmastertech :

I doubt this will fix the heating problem. It is more for long term prevention.

catmastertech :

Something is obviously wrong and needs attention.

catmastertech :

Pump pressures should be checked and well as flow settings.

catmastertech :

Machine should have some indication of a problem.

catmastertech :

Speed should be slower or faster than normal.

catmastertech :

Or it may be weak or stronger than normal.

catmastertech :

Stump work is very hard on this machine but, as long a you are just digging out the stumps it should not be any issue.

catmastertech :

Of course, the machine is too light to really lift out the stumps. Even a 320 is too small.

catmastertech :

330 and larger machines are recommended for heavy duty land clearing.

Customer:

I take my time and dig the stumps out...understand the limitations of the small machine...it's just digging holes beside the stumps till they will come out of the ground...and yep something is wrong...my cat mech had me change a setting from U1 to U3 and I wonder if that brought this on...I have reset to U1 but the heat problem continues. now i'm looking for the answer...what went wrong?

catmastertech :

U3 will only perform to how it was setup. Not much of a change on operation.

catmastertech :

I would use the top button for max lift speed.

catmastertech :

I still believe something is wrong with the performance. Speed or power should be off somehwere.

catmastertech :

Jerky operation would point to the return flow check valve causing a problem.

catmastertech :

I have seen this in larger machines.

catmastertech :

Cooler flow could also be a problem but, temperature in the bypass valve would be higher than the cooler.

Customer:

sounds like I got to have an on site Cat medic...

catmastertech :

If you cannot find temperature problem with the oil cooler or bypass valve then, that would be next.

Customer:

where is the return flow check valve? and how do I check it's performance?

catmastertech :

Infrared heat guns are cheap. You only need to use them up close.

catmastertech :

It is in the return lines from the main valve to the oil cooler.

catmastertech :

It looks like a large aluminum block.

Customer:

I got one...that's what convinced me to quit work. temps are too high for the good of machine and seals, etc.

catmastertech :

Maybe four inches

catmastertech :

across.

catmastertech :

You may see two blocks. One is the return flow check valve and the other is the oil cooler bypass.

catmastertech :

The one next to the valve is the return flow check and the one closer to the oil cooler is the bypass.

Customer:

where are you? what time can you be here in morning?

catmastertech :

No, I will be out at my day job.

catmastertech :

I will be back in after 7 pm eastern time.

catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,998
Experience: Field service technician for CAT 19 years.
Verified
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catmastertech
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,998
3,998 Satisfied Customers
Experience: Field service technician for CAT 19 years.

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