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Cat D6H LGP 2 overheating engine (coolant restrictor?)

JAJ

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Mar 22, 2022
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Owner operator of small fleet
Buy 5 shims by all means + all the other replaceable bits of the converter outlet relief valve, not just the spring.

I would suggest that you start with maybe 3 shims and go up or down from there to achieve the specified pressure. Remember that you have to test the converter outlet pressure with the oil at normal operating temperature, around 80C as a minimum.

I’ll have a look at the parts tomorrow regarding the springs, etc.
Thanks Nige
I was thinking about getting a full new valve but there is a bit of a wait for one and just checked there is for a valve spool as well (might call and check air freight). I will have a good look at the surfaces today but, I was thinking do new springs and seals and see how it went. I figured it would be a cheap way to test it if it looked ok otherwise, but would you replace the spool as well?
If the surfaces (body or spool) were questionable I thought get a full new valve and start fresh and remove all variables.
I will post a couple pics later

Re testing, I think with the temp gauge reading out, I was testing too cold before and it was only just in spec I think.... but i cant find my sheet from testing it when we did the pump. Ill try and find my numbers but the testing recently seemed like the valve wasn't closing and the pressure was going up and down with the revs.
 

JAJ

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Owner operator of small fleet
IMG_4305.jpegIMG_4310.jpegIMG_4306.jpegThe plot thickens…. The part number on the valve is not the correct one for my machine and says 42psi on the tag. The part number should be 9w-5596.
I found a diagram online for this valve (3T-6607) and it seems to show what came out of this one and does say D6H but Cat no longer lists it.

The valve spool looks ok (no scratches) but the body has had some scratches honed out it seems and a little loose. Disregard the fleck of paint in the body that was me and not in there when it came apart.

Might be safer to get a full new valve and start fresh I think!

It has a remaned torque converter from some stage so I wonder if the valve came with it from its original home.
 

Cmark

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Your 3T6607 valve updates to the later 9W5596 so I would say your assumption that the valve came with a reman torque converter is right. This should not affect your torque converter temperature though. The outlet relief is there to control the minimum pressure, not maximum.

The system relies on getting a large volume of oil to flow through the torque converter to carry away the heat to the cooler. This large volume of oil then goes to the transmission lubrication system, hence these questions:

What torque converter outlet pressures are you getting?
What is your transmission lubrication pressure at high idle?
 
Last edited:

JAJ

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Mar 22, 2022
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Location
Australia
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Owner operator of small fleet
Your 3T6607 valve updates to the later 9W5596 so I would say your assumption that the valve came with a reman torque converter is right. This should not affect your torque converter temperature though. The outlet relief is there to control the minimum pressure, not maximum.

The system relies on getting a large volume of oil to flow through the torque converter to carry away the heat to the cooler. This large volume of oil then goes to the transmission lubrication system, hence these questions:

What torque converter outlet pressures are you getting?
What is your transmission lubrication pressure at high idle?
Hi Cmark
Thanks for posting.
Found my videos of the most recent testing.
Torque inlet pressure (stalled 3 gear hot oil): 53 psi
Torque converter outlet (stalled 3 gear hot oil): 30 psi
Transmission lube pressure (not stalled high idle hot oil): settles at 32psi

I was thinking that if the pressure was to low in the torque converter that could mean it might generate some extra heat from not enough resistance... I could be completely incorrect though, what would you expect that could cause? Very interested to hear what you think about the pressures.
Thanks for your help.
 

Cmark

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was thinking that if the pressure was to low in the torque converter that could mean it might generate some extra heat from not enough resistance...
Low pressure should not be a cause of overheating per se. It is more of a symptom, indicating low flow not taking enough hot oil away to the cooler.

Low pressure means either one of two things:
1. low flow which can't keep up with the natural leakage in the system.
2. Correct flow but too much leakage in the system.

Have you checked main relief and priority valve pressures?
 

JAJ

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184
Location
Australia
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Owner operator of small fleet
Low pressure should not be a cause of overheating per se. It is more of a symptom, indicating low flow not taking enough hot oil away to the cooler.

Low pressure means either one of two things:
1. low flow which can't keep up with the natural leakage in the system.
2. Correct flow but too much leakage in the system.

Have you checked main relief and priority valve pressures?
Yes I have checked the pressures before and all others were in spec then. I need to recheck them all again to make sure now though. I have been troubleshooting a problem with my loader’s transmission as well and I have got the two machines a bit mixed up with the required specs so I do apologise.

I have mixed up the trans lube pressure spec for certain! I thought it was 27psi +-7.5 but I rechecked the spec sheet and it is 37psi +- 7.5 so you are absolutely correct re low flow with that in mind. The oil was over 100*C (can’t remember exactly) when I got the trans lube reading so I thought that may help account for the lower pressure. Not sure how much though?

So I think I will start again once I put the TC outlet relief valve back on and with the oil about 80*C (think that’s the spec per the testing procedure, will double check) and get all the numbers and post that.
I also want to check inside the back inspection plate on the transmission for leakage on or around the control bank to rule that out.
 

JAJ

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Owner operator of small fleet
So I installed the new springs in the Torque converter outlet valve and started with 3 shims. Then reassembled it to check.
Stalled
@85*c = 54psi
@100*c = 53psi
Lube pressure after driving around for a while to heat everything up properly.
@85*c = 40psi then dropped back and stabilised at 36psi high idle.


So I think that should be almost spot on for the lube pressure and I need a couple extra shims in the TC valve to bring it up to exactly where it should be. It is now in the allowed amount though. 60psi +-10psi
The tractor feels a lot more responsive and seems to drive easier at lower revs ( if that makes sense). So I think and hope this will make a huge difference, but need to work it hard for a day and see. The ambient temp has dropped off for autumn so it may not show up till next summer if it is going to get really hot again.

I haven’t rechecked the other pressures again yet but will do it and posted them when I get a chance.

Interesting to note it seems like from what I read that the D6H series 1 had the TC outlet valve like I have, set at about 42psi. The part numbers appear to be the same for the valve body, spool and even the big spring. Seems it was changed to a double spring setup at some stage (I assume series 2) and the spec raised to 60psi. Would be very interesting to know why they did this if anyone knows?
 

JAJ

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See attached Servie Mag from 1987.
Very interesting!!! Thanks for posting this!!!
I am mentally wired to want to know “the why” behind everything. So this satisfies my hunger for information on this matter.

Also interesting is the pressure spec for the new valve assembly in vehicle is 56 +-2psi and the testing and adjusting in the machine manual is 60 +- 10psi.
I assume it might be best to aim for the tighter spec of 56psi?
The bigger amount in the machine manual allows for the variables of each machine and oil temp “in service” I expect, not sure.

What would be best practise for the adjustment 56 or 60psi?
 

Nige

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G..G..G..Granville.........!! Fetch your cloth.
What would be best practise for the adjustment 56 or 60psi?
That SMag is over 35 years old. Things can change in that time span. I would use the newer spec but quite frankly a lot depends on how accurate your gauge is when measuring pressures this low. I think the quoted Cat gauge for TC outlet pressure measurement is 125psi max, Personally I’d be more comfortable with one that maxed out at 75 for better accuracy. Either way if a cheap inaccurate gauge is used you’ll probably be doing well to get the “real” pressure within +/- 10psi anyway, despite whatever the gauge might show.
 
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JAJ

Well-Known Member
Joined
Mar 22, 2022
Messages
184
Location
Australia
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Owner operator of small fleet
That SMag is over 35 years old. Things can change in that time span. I would use the newer spec but quite frankly a lot depends on how accurate your gauge is when measuring pressures this low. I think the quoted Cat gauge for TC outlet pressure measurement is 125psi max, Personally I’d be more comfortable with one that maxed out at 75 for better accuracy. Either way if a cheap inaccurate gauge is used you’ll probably be doing well to get the “real” pressure within +/- 10psi anyway, despite whatever the gauge might show.
Yeah I have cat gauges but I think they are 145psi and 575psi, I have the part numbers. When I was at the hydraulic shop getting all the parts to put the rippers on this machine I got another set of STAUFF gauges in 86psi and 45psi so I can test stuff more accurately at the lower pressures. They seem high quality. I was using the 86psi one on this but had to be careful while it was cold not to go off the dial now. So I think the valve may have been stuck or the spring was buggered before.

I got the 45psi gauge to test the trans lube pressure on my loader transmission to make sure before I commit to pulling it out. I should start a thread for it actually and see if anyone has ideas before it comes apart.
 
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