93 cat 312 not cooling down fast and looses power

[Nige]

I don't have SENR6135 but I'm going to try to get hold of a copy.

Replaced by SENR6137. It comes in 3 sections - attached.

 

[digger_hunter]

Hydraulics getting hot will cause the machine to slow down. In Cat 312's the problem has usually been down to

-Faulty master relief valve causing pump to go to full swash
-Fault hydraulic bypass valve causing hot oil to be dumped into tank directly (check if tank is getting super hot)
-if you could give a full description of the problem how it happens and what happens in a more detailed description I think we can nail it down quickly.

With the alternator there have been some cases the battery light has come on due to problems on the main computer misreading and you will find the battery charges ok and in most of the cases is a faulty rectifier within the alternator that throws it off and then usually the battery charging is affected

 

[aubuchon72786]

Ok so currently as we speak I have a battery light on, when I run machine she starts off great plenty of power other than my tracks I need to to do a rotary manifold, I'd say it's good power wise until just about the hydraulics get to the halfway point and it starts to slow down and loose power and motor begins to bog under a load, it looses allot of power half temp and past half temp, I did buy a new prv valve and put it in but the issue seemed to get much worse so I put the old one back in

 

[digger_hunter]

so if you put a PRV in you need to calibrate it. Have you tried running it in manual mode (flick manual switches on right hand side and left hand side of arm rests) and see if the problem improves.

I think the problem is the hydraulic oil is overheating (should be around 60-65C max). So the hydraulics would slow down. Is the hydraulic oil actually getting hot/too hot? have you checked the temp with an IR gun or something?
Could be that the oil is getting hot so the PRV is not able to relief the pump correctly and thats leading to engine bogging down as well.

first determine if the oil is actually getting hot regardless of the gauge on the display. and if thats getting hot you need to check the bypass valve and the master relief valve to see if thats what's causing the oil getting hot.

 

[aubuchon72786]

I've hit it with a gun once I go past halfway pump is like 184 which is hotter than I'm used to

 

[digger_hunter]

to calibrate the PRV accurately you need a 0-50bar pressure gauge and tweak the PRV pressure range using the display. theres. a whole procedure to that and maybe Nige can share the part of the manual thats how's how to do it. you could do it without a gauge and ballpark it after a few attempts as well in case you can't access a gauge.

 

[digger_hunter]

I've hit it with a gun once I go past halfway pump is like 184 which is hotter than I'm used to

yeah thats too hot man and the machine would slow down for sure at those temps

 

[digger_hunter]

I think the battery lights a bit of a red herring, the problem is in your hydraulics. Do you notice that you have to run the machine at higher revs when you first start it to get it to work at a decent pace? that could point to a relief valve issue. otherwise I think this could be yet another bypass valve.

check the tank when the temperature is going up periodically and if the tank is getting hot then its the bypass valve. we have loads of these on all Cat 312/b/c etc and most of teh time people end up tearing up everything else before locating that tiny valve behind the main control valve. its so small you would never expect it to cause so much hassle. Its the hydraulics systems version of a thermostat so does exactly the same thing when it is and when its not working as the engine thermostat would do.

 

[aubuchon72786]

Takes for ever for hydraulics to cool down also, u have a Pic of a location of it? Possible it's jammed up or when they go they go? Would it cause engine to bog like it's under a load?

 

[aubuchon72786]

I do have a hiss in the valve bank that's been there since I've owned it

 

[digger_hunter]

Well since the pump is not producing pressure and flow as per target the negative control system would cause the pump swash angle to increase and put more load on the engine. So it could cause the engine to bog down.

so the return flow out of the control valve goes into a T and one side goes to tank and the other to the hydraulic cooler. Theres a nut that holds the valve in place and if you remove that its just a spring and a valve sort of device. We used to jam a few coins to hold the valve closed permanently as it was a tropical climate and we didn't really have a use for the warm up function!

 

[aubuchon72786]

Thanks man I will try in the morning, would it cause a loud hiss

 

[digger_hunter]

Thanks man I will try in the morning, would it cause a loud hiss

not sure, could be the normal return noise. it could be related but can't be sure. one way to quickly check is that the return line to the tank should not get super hot because the valve should be shut, but quickest way to eliminate is to take the think out, jam it with a few appropriately sized coins and hopefully it fixes the problem pronto

 

[digger_hunter]

I would do that as it would take you far longer each time to wait for hydraulics to cool to diagnose the problem "the correct way". you could just jam the valve first thing and see if that works first otherwise you won't be able to touch anything there with the hydraulic oil hot

 

[aubuchon72786]

You just put coins on top of the spring to hold it down?

 

[uffex]

Good day
Loading hydraulics I would suspect to be the cause, high flow forced through small orifice. The pump is a common Kawaski, I would guess this is not backing down as it should. Are there any witness marks that the regulators have been disturbed ?

 

[Nige]

I've hit it with a gun once I go past halfway pump is like 184 which is hotter than I'm used to

184F on the hydraulic oil isn’t anywhere near hot, probably about normal if I’m being honest. Without looking I would say the high temp alarm probably goes off somewhere around 230 or so.

 

[uffex]

Good day
If the motor is loading it could be a symptom of failed pump regulation see attached may be of help.
Kind regards
Uffex

 

[aubuchon72786]

yeah thats too hot man and the machine would slow down for sure at those temps

So pump is 186, going into cooler 167 and leaving cooler 146, oil looks burned

 

[digger_hunter]

so cooler is working. have you checked the pipe that goes to teh tank from the main control valve? and temp of the tank?