I've been working on a 1977 Liftall 8000 lb. forklift powered by a 300-I6. I replaced rings and bearings several months ago because it had a broken ring and only ran on 5 cylinders. The water pump was also shot, so I replaced that. It runs great, but gets hot. The temp gauge wasn't working, so I replaced the sender and have checked it with a thermometer and it's only off by a few degrees, could be the difference between the temp at the back of the engine where the sender is and the top of the radiator where I put the thermometer in. I have flushed the cooling system, had the radiator checked for flow by a shop, they said it was only about 20 percent plugged up and should still cool fine (the guy I talked to on the phone at Liftall agrees, but he'll happily sell me a new radiator for 900 bucks anyway). I had the coolant checked for exhaust gasses, nothing there so it's not a cracked head or bad head gasket, I've installed a heavy-duty flex fan and a fan shroud, and a 180 degree thermostat. (There wasn't one in it, the Liftall guy said 180 was right for that, and that's right where it should run, even in 90+ degree heat. The radiator guy and I are both thinking that the water is not flowing through the engine like it should, is there a place where some scale might have plugged a water passage in the block? When I had the head off I flushed the crap out of it, but didn't have it hot-tanked or anything. It was flowing pretty good and clean. The radiator is small, but the Liftall guy said that it is more than adequate, and he thinks it's bigger than a truck radiator (I don't think so, the core measures 15" tall X 22" wide, 3 rows thick) down-flow style. If you are looking in the top of the radiator with the engine running and have someone rev the engine, you don't see any change in water level or velocity, in fact you don't really see any movement at all. When I start it up from cold, I can get about 20-30 mins. work out of it before it's up to 220-230 and I have to cool it down with a hose, spraying the radiator. It cools down to 180-190 very quickly, but then I only get 10-15 mins. out of it before it's right up there again. Hope someone can help me, we've some hard work planned for this thing over the next couple of months. Thanks, -TD

 

Maybe your waterpump is bad? Try that. It's all i could think of. Sorry i couldnt help you more, but i'm really stumped. Maybe that plugged radiator got worse? I would change the radiator out or take it to a radiator shop. They'll be able to help you out.

 

It's a new waterpump (well, rebuilt actually) and I was talking with the parts guy at NAPA where I bought it to see if they had any pumps from that rebuilder that didn't seem to pump. He admitted to some other problems, but not that one. I'm going to pull it tomorrow anyway, just to check it and to try to flush the block out again. I don't know what else to try at this point. Radiator was at the shop last week, ran hot before they worked on it, ran hot afterwards. You think you're stumped? Try it from where I sit! Thanks for the reply though! -TD

 

I had a similar problem on a Chevy Cavalier with a 2.2L four banger. My cousin owns it. A few months ago, with about 150,000 miles on it, the water pump started to leak, and I changed it. Unfortunately, since this pump has been in use a very long time, the auto parts store gave me a replacement for a "V" belt application (I.E. Standard rotation) when I needed a pump for a serpentine belt (I.E. Reverse rotation) application. The end result was overheating. You might want to make sure that you have a standard rotation pump.

 

Yes, the first pump I bought was for a newer engine, it had a thicker shaft and a different hub, had to go back to get the right one, he had to match it up by casting numbers and said it was an early pump, so it should be right....maybe! -TD

 

Why a flex fan? I would think that you would want that fan pulling air across the radiator all the time, even more so when the revs are up. Doesn't the flex fan flatten out at higher rpms and provide less air flow? I think that a solid fan pushing air all the time would be a big help. We have a toyota forklift were I work and thats how its set up.

 

First of all make sure that the impeller on the pump are pointed the right way. When they started running serpentine belts on on engines and turning the pumps backwards they created a nightmare for the rebuilders I have gotten pumps that where the right part number but had the the wrong impleller on them. And they do show these exact symptoms. It is flowing just enough water that when you spray water on the radiator it will cool down.

 

Yes, flex fans do flatten out at higher rpm, but this rig doesn't see high rpm. We need all the air movement at low engine speeds, most of the time it's running at about 1500 or so, only short blasts up to 3000-3500. As for the waterpump, I took it back off today and double-checked the impeller, it's the right one for a std. rotation pump. I even took it down to NAPA and compared it to another one, same thing. I flushed the hell out of the block and head, checked the thermostat by putting it in a can of water with a thermometer and putting a torch to the bottom of the can. It opens normally. Put everything back together and ran it up to operating temp, cross-checking between the temp gauge and the themometer in the radiator. Got up to about 195 and seemed to hold there, but that's with no load. There does seem to be a good deal of flow visible in the top of the radiator, I'll run it tomorrow with a load and see what happens. I think it's pretty much gotta be the radiator, I think it's in worse shape than the kid at the radiator shop thought...maybe it's time for some high explosives! -TD

 

There are several things that have either been done and not posted here or not done at all that could be causing your overheating. The first thing is the replacement of rings and bearings. Is that all that was done, or is it a complete rebuild? If that's all that was done you should expect to have some problems. What's the timing set at? Is it advancing properly? Is the fuel supply adequate? Incorrect timing and lean mixture are common causes for overheating. The flex fan is probably not helping matters. I would install a regular fan. A forklift will never move fast enough to draw sufficient air to cool a 300 without a good fan, especially with the radiator in the back where it isn't exposed to the airflow.

 

Yes, it was a ring-and-bearing job, not a complete rebuild. Running 6 degrees BTDC on the timing, vacuum advance functioning correctly. Good fuel supply, correct jetting in the carb judging by the plugs. It does run a little cooler with the flex fan than with the stock fan, I was trying to increase airflow through the radiator since there is no ram air effect. I installed the flex fan and the shroud at the same time, maybe I'll put the stock fan back on but leave the shroud in place. Thanks for the responses so far. -TD

 

Not sure if a forklift would have any type of EGR valve setup since emissions aren't an issue, but some engines designed for EGR applications can run 15-20 degrees hotter if the EGR system is disabled or malfunctioning. Seems "backwards" that hot exhaust would cool an engine, but by diluting the intake mixture there's less fuel to burn which = less heat produced. Yes this does zap power, but we're concerned with operating temp and not 0-60 times :-)

$900 for a radiator? Slick all aluminum custom jobs run half that. I'm sure you could find a $150 "stock" radiator which will work with minor modifications. If the radiator does check out you might consider installing an electric fan. My six would run a bit hot in slow traffic with the stock belt driven fan, but with a dual electric fan setup from flex-a-lite it stays cool and happy.

 

It is probably the radiator I did the samething with a tractor one time overhauled it and the radiator wouldn't cool it had radiator rodded and cleaned no issues after that

 

No, no EGR on this puppy. Just for fun I put the stock fan back on today, but with the shroud in place and worked it around the yard a bit, it ran about 10 degrees hotter than yesterday with the flex-fan. The ambient temp was about the same yesterday and today at the time I was running it. I've though about an electric fan, but with everything working properly it shouldn't need one. Monday I'll look into having this one re-cored, maybe with a 4 row core instead of the three row. I might do a little junk-yard scrounging to see if I can find something that will fit, but it's such an odd size. -TD

 

I think it's air in the block. Try parking the lift down ward on a decline (like a truck pit). Let it sit over night.

 

I had the same problem on my truck about a year ago. The water pump went out and I replaced it. In doing so, I damaged the fan clutch. I decided that a flex fan would be the best replacement, as I had used them before on other engines with a noticeable power increase and more than adequate cooling. I picked up a large one (18 or 19 inch- can't remember now) after measuring the diameter of the original fan. I didn't get a cheap crappy one either- it was a major name brand. Anyway, the truck started overheating immediately. I started checking everything. The fan matched up well with the shroud and seemed to be pulling plenty of air. I thought I'd gotten a backward pump, because water didn't seem to be flowing much. Found partially clogged radiator and changed it. Changed Thermostat, removed thermostat, etc, etc. Finally re-installed original fan with new clutch and cooled perfectly. The thing that really got me was that it didn't even seem to cool out on the interstate where the fan should have been irrelevant. I'd look closer at that situation if I were you, or maybe the electric. The thought of air in the system is a possibility too. One other thing to consider is if the new rings have seated properly yet. I had a head-scratcher on a 350 Chevy once that wanted to run hot after a rebuild. NEW EVERYTHING in the cooling system, including a rebuilt pump with the old cast iron impeller that moves more water. It was a project car and had only a few hundred miles on it, but after a good interstate trip it started cooling normally. There's a lot of additional heat generated on a rebuilt engine sometimes until everything is broken in. If the radiator itself is getting hot and can be cooled with a hose, and thereby cools the engine, then it's probably not a water flow problem. This indicates that the engine heat is being transferred to the radiator, but the radiator is not exchanging heat with the atmosphere. If it was adequate before it should be now. That narrows it down to 1.) airflow to allow heat exchange, or 2.) Engine is actually generating more heat to be dissipated than it used to.