1971 CAT 977L Coolant in Hydraulic Oil

[Aaron.Phillips07]

Good evening. I have a 1971 CAT 977L with a D333C. (Serial 70J1348). When I purchased this machine, it had very milky fluid and I have since flushed the system out twice with cheap Tractor Supply fluid, new filters for each flush, but somehow keep ending up with (what I thought to be water) in the hydro oil. Turns out, it is engine coolant.
* There is no coolant in the engine oil
* There is no Hydro oil in the coolant
* With fresh Hydro fluid and filters, it takes about 1.5 hours for 2 gallons of coolant to make its way into the Hyrdo oil system. No aeration is present from what I can see.
I have the parts manual and service manual(s) for this machine but I'm not seeing anything where it shows the cooling system tied in with the Hydro system unless I'm blindly overlooking something? I wanted to ask for your help on this one and see if anyone has any ideas of where this might be occurring. As always, thank you to all who have been so kind and helpful to me.

-Aaron

 

[Welder Dave]

You asked in the other thread too but is there an oil cooler on the bottom of the rad?

 

[pittsburgh cat man]

I'm pretty sure hyd cooler is air to oil located beside the radiator core

 

[Aaron.Phillips07]

The oil cooler is next to the coolant radiator. It is about 10” wide and the same height as the radiator, same material and design. Just a smaller skinnier version.

 

[Nige]

Turns out, it is engine coolant.

Can you clarify how you determined that please.?

When this happens does the fluid level in the hydraulic tank rise.?
If you drain the fluid level back to the same level as it was before what quantity do you have to drain out.?

Does the level of coolant in the radiator fall during the same period.?
How much fluid is it necessary to add to get it back to the previous level.?

 

[Aaron.Phillips07]

Here's what happened two times in a row identically.
I changed out Hydro fluid and filters-->topped off radiator coolant-->warmed machine and cycled through bucket movements slowly to circulate new fluids-->ran for 1.5 hours.
-
After each of the two times, I was exactly two gallons low on coolant and exactly 2 gallons overly fully in my Hydro tank. I did some more digging into my parts manual and my brother also looked very closely at connections with me. It seems like the culprit is likely the oil cooler? It is split into two parts, one side seems to have the oil loop through and the other side has the coolant. If the coolant is higher in pressure, that would explain why there's no oil in the coolant. Does this sound familiar to you guys?

 

[pittsburgh cat man]

11k hyd cooler can’t imagine yours would be different there is no connection to antifreeze

 

[Nige]

It seems like the culprit is likely the oil cooler?

If your Parts Manual shows the same as mine then the oil cooler for the implement hydraulic system is not a conventional heat exchanger (oil to coolant) but is mounted on the LH side of the radiator assembly and is cooled by the air flow created by the fan through the radiator assembly (oil to air). This is why we’re struggling to explain how coolant can get into the hydraulic system via said cooler.

 

[Aaron.Phillips07]

I completely agree with you Nige. This has been a bit of an odd issue. My brother was able to clean away some of the old gunk around this part of the system last evening and found the part number: 8N4914 on the cooler. Date stamp of 6/79. This machine worked in a rock quarry most its life and someone definitely beefed up the front radiator grill. I'm now guessing that the original cooler was damaged and replaced in 79.

 

[Aaron.Phillips07]

I'm going to be working this afternoon/evening to remove the oil cooler and 100% verify that it does in fact have an oil AND coolant line(s) running in and out of it. Have you guys ever seen something like this before? The manual and parts book in this sense have been very hard to figure out.
Attached is the picture of the cooler from my parts manual.

 

[Nige]

Can you post some photos of the hydraulic oil cooler just to confirm please. The parts manual for the 70J ma chine is not available online. The 8N-4914 cooler was fitted to 70J machines from S/N 953-Up. i checked a few places and everything shows an air-to-oil cooler not an oil-to-coolant cooler. if that is correct then on the face of it there appears no way that the cooler could be the source of the transfer of coolant to the hydraulic oil. Illustration below from an 11K parts manual.

I'm going to be working this afternoon/evening to remove the oil cooler and 100% verify that it does in fact have an oil AND coolant line(s) running in and out of it.

Is there any possibility that some lines to the cooler might have been hooked up incorrectly.? I don't see how that could happen but it is a box worth ticking.

 

[Aaron.Phillips07]

Very heavy winds today. I wasn't able to attack this outside but will update tomorrow if the wind calms down. In the meantime, I have found quite a few places that make OEM replacement parts for the 8N-4914 part number and they all have separate compartments for oil/coolant. At least from what I can see. Here's one for example: Radiator Supply House 8N-4914 Direct Replacement OEM

 

[pittsburgh cat man]

You do know that is a transmission cooler too two lines for hyd oil two for transmission oil. I just had a thought when you filled the anti freeze did you bleed the block We always loosened the water temp sensor to let air out of block This could possibly why you are adding coolant

 

[interv8]

Can you post some photos of the hydraulic oil cooler just to confirm please. The parts manual for the 70J ma chine is not available online. The 8N-4914 cooler was fitted to 70J machines from S/N 953-Up. i checked a few places and everything shows an air-to-oil cooler not an oil-to-coolant cooler. if that is correct then on the face of it there appears no way that the cooler could be the source of the transfer of coolant to the hydraulic oil. Illustration below from an 11K parts manual.

View attachment 357396


Is there any possibility that some lines to the cooler might have been hooked up incorrectly.? I don't see how that could happen but it is a box worth ticking.

A mate had diesel in his jd3650 tractor, the tech couldnt work it out, till old mate had a look, there,s the problem, the lines were hooked up wrong. Sometimes it can be overlooked and a fresh set of eyes is valuble. Cheers