UNI-SYSTEM 704

[Anonymous-0]

Hi all. I have some questions about our 704 power unit. We bought it about 5 years ago after our 400 Farmall burnt with a New Idea 319 mounted to it. Anyway it has a husking unit on it with a 4 row head. We have had nothing but problems with it since we got it. Right now as of last fall it overheats and shuts down every load. We've put several different kinds of thermostats in it still nothing we clean the radiator in it all the time with air and water. It has had 2 water pumps it it too. It is constently running coolant out the overflow after you idle it down. The dealer just tells us that it is a common problem that they have no solution to. Would it help it we put the exhaust on the outside of the hood because the mufflers are about 3 inches away from the radiator and that doesn't help I am sure. I also thought about putting an electric cooling fan on it to help with the overheating. Next problem is the left brake will lock up just all of a sudden sometimes. It doesn't do it if that wheel is on the lower side of the hill. Some times is worse than others sometimes it just jerks a little and the next it might spin a 180 right in the field. Seems to be worse at low speeds. It has a GMC V-6 gas in it. Any input would be appreciated cause if it is going to cost too much we are going to get rid of it and get a combine I think. Frankly I don't think my dad should have bought one that is a gas. The old 400 would pick circles around this piece of junk and it was only 2 row.

 

[Anonymous-0]

Probably I would consider a new core in the radiator. Wouldn't be surprised if the old one wasn't properly maintained and has too many deposits. It is possible to "rod out" the core on many radiators, but you have to able to remove the bottom and top tank without destroying the core, which might be difficult on an "automotive" type radiator which I assume this machine uses. If possible on the new core, go to higher fin density. A copper core would be a great help, but that would be prohibitively expensive.

 

[noncompos]

I'm not familiar with either your engine or your 704; the following are just general things...
Flushing with air and water will clear out loose stuff, but not accumulated scale, which can slow heat transfer to the air (see rodding comment).
Shine a light (at night) thru the radiator, to see if airflow is diminished by dirt, chaff.
Is it shrouded?? If not, room to Mickey-Mouse a shroud?? Hoses good, not spongy inside??
By all means get all the heat out of the engine compartment/away from the engine that you can; mufflers next to a radiator sounds really weird...
Is the air entering the radiator cool, or coming over something hot, sending warmed air into the radiator??
You might also check some of the Chev or GM car sites, to see if their archives show the V6 has a lot of cooling problems.
I assume no water in the oil, oil in the water, or bubbling when idling that would indicate head gasket or cracks that let hot combustion gases into water.
The archives here will have many more suggestions. Good luck.

 

[bradley martin]

I doubt that you can afford to keep the 704...with the price of gas and the appetite of thatGM 401 V_6, you would soon pay for a 707 or 708 w/ the perkins 354. Moving one of the exhausts outside the hood does help but those girls all ran hot. I have run at night with the 729A sheller and there was 2 blue flames shooting out about 2 feet constantly. I finally saw the light 3 yrs ago, running in 200 bu., down corn and a fuel cost of $20/ A. You could likely double that now. With scrap near $300 ton, you can likely get out of it and into a diesel for very little cost.

 

[Anonymous-0]

Thanks for the info guys! To answer a few questions. The engine has two mufflers that sit right above the radiator under the hood and exits right above the radiator so I'm guessing that the hot exhaust is being sucked right back through the radiator so I thought if I could get the mufflers out from underneath the hood it would help. Also it does not have a shroud. I was wondering if we could run it without a thermostat so the engine wouldn't warm up so fast? But we are really concerned about the brake issue. Any suggestions?

 

[bradley martin]

The fan on the 704 is "pushing " not pulling air through the radiator..i.e. the air is drawn from the engine compartment and out through the rad...backwards to a tractor Auto or truck.As stated in my previous response, if you move one of the mufflers even to the ouside, it will make a difference but these engines run hot. That is why so many of them burned. As for your brake issue, are you sure that it is the brake and not the final drive that is locking up? The brakes are airly basic and easily accessed. Check for corrosion or a broken spring.Personally, I would not spend a lot of time or money fixing or modifying a 704.

 

[Anonymous-0]

No, don't run without a thermostat. Coolant flows too fast to cool properly and you will make things worse. However, you can use a piece of metal (usually a small copper or aluminum rod) to lodge/jam the thermostat in the open position. Depending on the style of thermostat you might need to use three small rods around the perimeter or a single one in the middle. This will retain the desired flow restriction and allow maximum cooling.

 

[Anonymous-0]

Are the final drives common for going bad on these? If so are they better on the 707 or 708? Are the combines any good for the UNI-SYSTEMS? We only plant about 100 acres of corn so it isn't something that is going to be used alot. And we don't try to win any races when picking corn. Thanks!

 

[Anonymous-0]

A fellow student which graduated in my class went to work for NI for several years as a design engineer working primarily on the platform heads. He claimed the model 708,and I believe the model 709 were much better machines. I don't have any experience, but did make a feeble attempt to get Dad to buy one in the mid 70's.

 

[bradley martin]

As with most machines produced over an extended period of time, there were continuous updateds and improvements and the UNI system was no different.The final drives were Rockwell I believe. The 708/709 were much more machine than the 704/705.(708 Perkins power. 709 Allis power). Final drives did give problems, often due to maintenance neglect. If you look closely at many Uni's, you will see where the final drives have been apart by the telltale squeezeout of sealant caulking. The last of the Uni's (800C.802C,&803C) used John Deere final drives and Cummins power.

 

[Anonymous-0]

Will the husking bed and head off our 704 work on a 708? I think the head is a 844 and husking bed is a 737.

 

[Ted(MD)]

Yes,

A 737 will fit both a 708 and 709 but you may need to have differant mounting brackets or make adaptors so check before you make a purchase. The old style like your 704 has uses a long bolt that pulls the harvester up tight in the rear while the newer version uses a large peg and hole to hold the rear of the harvesting unit on. Your 844 head and feederhouse will work the same as they always did.

Ted

 

[1031D]

Don't know much about uni's, but my old 1967? GMC C65 dumper has one of those 305's in it. We had problems with it running hot, and found out somebody switched it to one thermostat in the upper neck when it was supposed to have a 2 piece upper neck and 2 thermostats. I asked our local GM medium truck dealer about it and he said the 305 V6 required a lot of coolant flow to cool properly, so we switched it, never has a problem since. Also, is the timing right on the engine? Sometimes if the timing is too far advanced? it will make an engine run hotter than it is supposed to.