IH 674 Hydraulic schematic/diagram

Does anyone know where I can get a schematic/ diagram or flow chart for this tractor ?

Other than a dealer that still has the old ih books it may be hard to find.

What are to trying to find out about the system?

My brother and I have been working on my dads tractor. The hydraulics stopped working on it. We took the MCV off and found that the pump housing had busted the key was also sheared on the drive gear. So we installed a new pump. We ran the tractor at idle for about 20 minutes. We raised the front end loader up and down a few times as well as the 3pt hitch and turned the steering. All seemed to be working good. We hooked up a pressure gauge to check pressure. At this point the hydraulics stopped working. We pulled the MCV off again and found the pressure port O-ring and the seal on the pump plate were blown. We replaced these seals/O-rings. We have had all the spools/valves out and cleaned and checked them. The flow divider, relief valve, cooler bypass valve. We also removed the unload valve under the seat. Cleaned and checked everything and replaced all O-rings. Everything moves freely and looks good. We haven"t removed any of the control valves yet, could the problem be in there ? It seems to me that the pump is deadheading, blowing the seals. What I was looking for is some diagrams that show the hydraulic flow through the system. On the bottom of the MCV toward the back of the tractor the I&T book says the bottom line is pressure and the top line is return. Just thought if I could see how the system works I could figure out where the problem is. Before this happened everything was working good, brakes steering.

Thanks
Greg Wilburn

I would take out the pilot relief valve and replace with a known good one from most any IH tractor built since about 64. It is on the bottom of the mcv, is a cartridge type valve , has screen in the end. It may be stuck. Or, with a gauge installed, low idle you could cautiously move aux valve but it can build pressure so fast this is very risky if you aren't very careful. I believe the book calls for 2500 psi on that model which is a lot of pressue even when things are working correctly. Correct way of course is with an inline flow rater that has it's own relief valve. A dealer could print a page of the manual for you to observe flow and correct placement of all valves in the mcv. Several different places to get manuals, I would think this site would have them.

Hi Greg,
How is the loader control plumbed into the hydraulic
system?

JimB

(quoted from post at 16:21:05 12/01/10) Hi Greg,
How is the loader control plumbed into the hydraulic
system?

JimB

Click to expand...

We are using the aux valve. Looking from the back of the tractor it is the connection on the bottom. I talked to my brother tonight and he is going to get a known good pressure releif valve and try that.

Hi, do I understand correctly the loader is
connected via a single hydraulic hose from the
lower aux outlet at the rear of the tractor?
Do you lift loader via aux hydraulic lever or is
their a separate set of hydraulic controls for
loader? Does loader have hydraulic bucket? Does
loader have down pressure? Is their a return
hydraulic line from loader to where?

If you answer the above ? then we can help you
more.

JimB

(quoted from post at 16:32:46 12/03/10) Hi, do I understand correctly the loader is
connected via a single hydraulic hose from the
lower aux outlet at the rear of the tractor?
Do you lift loader via aux hydraulic lever or is
their a separate set of hydraulic controls for
loader? Does loader have hydraulic bucket? Does
loader have down pressure? Is their a return
hydraulic line from loader to where?

If you answer the above ? then we can help you
more.

JimB

Click to expand...

Yes, lift loader with aux. Just has pressure on the raise position. Bucket has a manual trip lever. We have completley disconnected the loader from the tractor, still has the same problem.

can I hook up loader hyd on my lift arm ports on a 674 Int