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Bill767 · 06-07-2019, 02:23 PM

An update, and a question. Like I said I had the pump rebuilt and thought I was good to go, unfortunately on a hard pull I am getting quite hot, up to 225 today. I have never had an overheating problem in the whole time I have had this coach, 144,000 miles. On the hottest day on a steep pass, I never saw more than 205. I am trying to figure out what rebuilding the pump would have to do with this, it's as if the fan is not spinning up. I wanted to pull over so I could see if it was on high when the temps got up, but no where to pull over. Any thoughts?

barmcd · 06-07-2019, 03:36 PM

That's not good news. I wonder if the pump is working?

RamiDav · 06-07-2019, 04:32 PM

I think you have pressure regulator in the pump
Maybe it is set to low

Bill767 · 06-07-2019, 05:10 PM

I don't think there is a regulator in the pump. But I do wonder if the pump is working also. Or if some gunk got in the line and plugged the filter, could that be a scenario? I am going to replace filter tomorrow.

Bill767 · 06-07-2019, 05:12 PM

And if the pump wasn't working would my normal driving temps be normal as they are. What could cause the fan with the wax valve to not speed up, a bad wax valve?

CountryB · 06-07-2019, 05:52 PM

i made this drawing for another thread (where a flow control valve was benign added) but it may be helpful in showing how the fan circuit works.

Basically when the wax valve is open (flow through it) the fan stops running.

So to test the fan and wax valve, remove the line at the wax valve and plug/cap it. Either remove both lines and cap both or remove one line and cap the line and plug the corresponding fitting - so no oil will be lost when the engine is started.

Then start the engine. With no oil flow through the wax valve the fan will full speed.

If it does run full speed, the wax valve is bad.
If it does not run full speed the fan motor (or switching valve mounted to the motor) is bad.

Bill767 · 06-08-2019, 06:26 AM

It sure seems suspect that this would happen right after the pump being rebuilt.

distaff · 06-08-2019, 09:48 AM

Not trivial to test the pump for flow and pressure on the coach. Normally this is done with the pump on a bench. Did the shop that did the rebuild do a flow/pressure test? Is there a record of it? One other thing - how often do you change your hydraulic filter and did you change it after the rebuild?

My usual test for fan/cooling performance is the climb up out of the Columbia river basis on I90 (from Vantage to the top westbound seems a stiffer challenge than the eastbound side).

My coach usually tops out at 205 before it drops back as you report yours used to, but I've seen it go as high as 209 on really hot days climbing at 99% power.

After putting in the the new Parker pump I am getting the same behaviour. I'm also running the original fan controller.

96 Wideglide · 06-08-2019, 05:03 PM

Quote:

Originally Posted by Bill767

I don't think there is a regulator in the pump. But I do wonder if the pump is working also. Or if some gunk got in the line and plugged the filter, could that be a scenario? I am going to replace filter tomorrow.

Wouldn't you have very hard steering if the pump wasn't working

.

CountryB · 06-08-2019, 05:08 PM

I'm not sure how DD does it, but CAT uses a separate pump for the power steering. It's driven off the engine front gear assembly, and the hyd pump for the fan is driven off the transmission PTO. They use the same hydraulic reservoir.

distaff · 06-08-2019, 11:14 PM

I dropped out of engineering when someone introduced the concept of liquid dynamics. I don't understand pressure vs flow that well, but my understanding is that power steering relies on high(ish) pressure but not much flow. A fan motor needs flow.

Could be the pump makes pressure until there is demand for flow. BTW, at the speeds you are driving when your rig overheats you would not notice a little drop in the power steering efficiency.

Having said that, pay attention to the bit where I said I dropped out of engineering.

Bill767 · 06-10-2019, 06:30 AM

Quote:

Originally Posted by CountryB

I'm not sure how DD does it, but CAT uses a separate pump for the power steering. It's driven off the engine front gear assembly, and the hyd pump for the fan is driven off the transmission PTO. They use the same hydraulic reservoir.

The more i look into this I think you may be right. Even though my manuals show the power steering and fan operation coming from the hydraulic pump, there appears to be a power steering pump mounted on my engine with the large line going to the reservoir and a smaller line going forward. I just drove 200 miles yesterday over several passes and with care I was able to hold the temp to 212, but I was able to pull over when the temp was high and my fan is definitely not running on high.

Bill767 · 06-10-2019, 09:32 AM

Okay, one more update. I swapped the lines to the wax valve this am. The fan did not go to high speed, it might have been a slight bit faster than it was with the lines in the correct place. So to me, it does seem to confirm my newly rebuilt pump is not putting out enough pressure to turn the fan on high. Would any of you like to confirm my thinking or would you not agree?

CountryB · 06-10-2019, 09:42 AM

It could be the pump is not putting out - or the "Switching" valve (attached to front of motor) is stuck closed and not allowing full flow through the pump.

Also there is a high pressure "By-pass" (pressure relief) in the hyd pump. If the by-pass was stuck open (or had broken spring) the pump would not be able to build enough pressure.

If some debris was in the system it could affect either/both the Switching Valve and/or the Pump By-Pass valve.
___

So if the Switching Valve is malfunctioning (do to some debris getting into the valve) - that is the not fault of the pump or rebuilder.

If the Pump Pressure Relief Valve is stuck open or has a broken spring, that is a problem in the pump (either someone did not flush the hyd system (and some debris then got it to the pump) or they did not clean/check the relief valve during the rebuild.

Was there any sign of metal debris in the hyd system before (or the reason for) the pump rebuild?