Cat 980G-coolant in transmission

I have a 980G that has been getting lots of coolant in the transmission after starting it this spring. I have a new trans cooler on the way. I removed the cooler today and pressure tested it-more to see where it was leaking than anything else.
Anyway to cut a long story short it looks like the cooler is not leaking,(pressurised it to 30 psi). Can anyone tell me if there is anywhere else that the coolant can get into the trans oil?

The only place that coolant and oil should get close to each other is in the cooler.

How much is lots?

Might be that the cooler only leaks when it is hot?

Are you putting pressure on the coolant side or the oil side? Should not make a difference but.....

I'm assuming you have ruled out error or vandalism?

Also not to sound stupid but you did remove and test the correct cooler?

Any chance of a S/N just to let one check in more detail?

Maybe 1/2 litre with in an hour. I have pressure on the oil side-like you say it shouldn't make a difference...
I'm testing the right cooler. The machine is in remote part of the Yukon so I doubt vandalism.... Serial number is
2KR04346.
I was wondering if there is a frost plug or similar in the end of the engine where it could get through to TC and trans...

My mind is a bit fuzzy on the G model Cats but didn't they go to a radiator type cooler for the transmission oil on them?

No it's cylindrical-21" long and around 6" diameter.

billfishnz said:

No it's cylindrical-21" long and around 6" diameter.

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Yep! Core should be a 7W0205 for new but it is available as reman or "Yellow Mark" under different part numbers.

To be honest I never got too involved with a 3406 engine so hope someone else more familiar with them can chime in on any core plugs that could leak to let coolant into transmission.

Below is a screen capture off SIS and the rear of block shows having a plug and seal #24 and #25 but I have no way of knowing if they are in the coolant passages or something else or if they are even in a place that could let coolant into the fly wheel housing.



That same plug and seal is used at the front of the block but still not sure what is inside of it!

hi, Even if there is coolant leaks at back of block it would be contained with in the flywheel housing and show up in the engine oil
I agree with ken that you need to check the cooler under operating temperature conditions
Mark

I believe flywheel housings on all the conventional drive train wheel loaders I have worked on are wet and have a drain directly to the bottom of the transmission drop box. You can follow the piping from the torque converter housing to be sure.

Mark250 said:

hi, Even if there is coolant leaks at back of block it would be contained with in the flywheel housing and show up in the engine oil
I agree with ken that you need to check the cooler under operating temperature conditions
Mark

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Not having any experience with getting that deep into a 3406 I was not sure if that plug was in the water jacket and was located somewhere that it could get into the transmission oil. I would just be guessing that the flywheel and pump drive gears ran in transmission oil but then the pump gears might also be lubed by engine oil.

One of the problems with trying to come up with ideas on a machine one never saw apart. Hope I didn't cause too much confusion!

John C. said:

I believe flywheel housings on all the conventional drive train wheel loaders I have worked on are wet and have a drain directly to the bottom of the transmission drop box. You can follow the piping from the torque converter housing to be sure.

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hi ,to clarify.
the flywheel side of the flywheel housing is a wet area of the transmission .
the engine side of the flywheel housing is a wet area related to the engine.
the rear crankshaft seal separates the two areas and this side would contain any coolant loss to the engine sump
Mark

Just thinking on this cooler, is it one of those that has molded rubber sealing the ends around the tubes? I'm wondering if by some strange luck the pressure on the oil side would be holding the "leak" closed while it is running and then when oil pressure drops and there is still some water pressure in the cooling system it then can flow into the oil, kind of like a check valve deal.

It might pay to make up some plates for the ends of the cooler core to put air pressure on the coolant side to see if that is what is happening. A few minutes with a couple scraps of steel should do the trick. I'd even start low, with say 10 psi pressure to see what happens. And if possible fill a tub with hot water to see if that makes a difference.

A bit unrelated to this problem but I once had a problem finding an internal coolant leak in a 16V-71 could not find a drop of water coming from any of the normal places with pan off and 20 psi into the radiator. Left for the day and came back in the morning to find a big puddle of coolant on the floor of the shop. Followed drip up stream and it was then obvious it was a bad water pump seal. For some reason pressure in the cooling system would make the seal work but with no pressure it would leak.

Hey guys thanks for the help. I finally got the new cooler sent in here and fitted it-no more coolant in the trans so I guess it must have been a 'one way' leak. Anyway we started sluicing today and the transmission light and warning light come on. I changed the filter when I fitted the new cooler and cleaned the screen this evening but the lights are still on. Can anyone tell me if it is just pressure related when the lights come on or does it have other sensors-maybe residue of coolant in the system that it detects etc etc. Any help you can give me would be awesome...I don't have an operator manual here but am looking online for that and the shop manual...

is this the light symbol that came on

For a downloadable Adobe pdf Operator Manual try this link ............ you didn't mention the machine Seiral Number otherwise I could have told you what publication number to search for. An Operator Manual is about $45, a Parts Manual around $90.
https://catpublications.com/Search/

Nige said:

For a downloadable Adobe pdf Operator Manual try this link ............ you didn't mention the machine Seiral Number otherwise I could have told you what publication number to search for. An Operator Manual is about $45, a Parts Manual around $90.
https://catpublications.com/Search/

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Serial Number was in post #3
"Serial number is 2KR04346."

This is what I find doing a search on 2KR:
https://catpublications.com/Search/recall?savedSearchId=e1ac6f94-fa7d-e811-9106-005056a270f1

Mark-yes that's the light.
I have an operators manual downloading now-thanks for the link.

billfishnz said:

Mark-yes that's the light.
I have an operators manual downloading now-thanks for the link.

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That light "should" come on only if the transmission filter switch is activated. I believe that is a normally closed switch switch #164-7577. I could be wrong but if you unplug the switch light would normally come on and if you jumper the contacts in the harness it should go off. Hope I said that right!

I see you have changed the filter at least once could be there is still some thing in there causing a problem.

I put the "should" in quotes because we had a problem with the "filter plugged light" coming on in a 988H and after chasing ghosts for months found the real problem switch was a temperature switch on the transmission control valve never got a good explanation of why that was causing the plugged filter indicator to light up!

Ken, I think the OPs 980G is a slightly different animal and not quite so high-tech as a 988H.
I would be checking the wiring of the plugged filter switch first, followed by a check of the switch to see if it’s opening and closing correctly. If that all checks out the next move would be to see if the bypass spool in the filter head is stuck/worn, or maybe if the springs have broken.
You’re correct in that jumpering the wire harness for the switch should put the light out.

Nige said:

Ken, I think the OPs 980G is a slightly different animal and not quite so high-tech as a 988H.
I would be checking the wiring of the plugged filter switch first, followed by a check of the switch to see if it’s opening and closing correctly. If that all checks out the next move would be to see if the bypass spool in the filter head is stuck/worn, or maybe if the springs have broken.
You’re correct in that jumpering the wire harness for the switch should put the light out.

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Yes it might be different but I checked and it uses the same by-pass valve switch. As I recall the switch is worked by a pin on the end over the by-pass valve that has a couple springs inside it. Easy to remove and test it's operation. Nice simple on/off switch either open or close contacts.

OK thanks.Changed the oil and filter this morning and the lights are staying off at the moment.
There is another issue though...
When you go from 1F and put your foot on the RH brake pedal-fairly hard-it shifts back into 1N. If you are gentle on the RH brake it stays in 1F as it should. Same when you are backing down the tailing hill in 1R if you put your your foot down too hard on the pedal it shifts back to 1N.
The park brake light and the brake pressure light also flash simultaneously for a split second as it shifts into neutral. Like I said if you are gentle on that RH pedal it stays in gear and neither brake lights flash on.
The foot brake also seem 'fiercer' than usual....
When using the LH brake it shifts back to 1N instead of just disengaging it while your foot is on the pedal.
Is there any way the trans/brake issues could be related?