After reading posts about the factory temp gauges being unreliable and horror stories about engines being fried from going over the 3/4mark I decided to install a mechanical and see what's really going on. BTW last July I did a trip to Alaska. It was very hot out and I was carrying a 2000# camper. I ran in the "third" segment most of the way on the factory temp gauge and on a number of hills I put the needle on the "H". No problems at all.

So the new gauge shows at just regular cruising to be 165*F, the factory gauge is on the division between the first and second segment. This is where the truck normally sits at when unloaded. No wonder why I get no heat in the winter!

Hooked up the Jeep and camper(6000#)and nailed it on a few hills. Due to the cooler outside temps the highest I could get the factory gauge was just into the third segment which showed 200*F on the aftermarket gauge.

So what are safe temps for our engines?

 

very good question. as i was getting worried on my temps when i towd last weekend.

EGT's were fine but i was backing out because of climbing engine temps.

on the up side it would keep pulling hard if left my on the floor.

jIMMy

 

I am in the same boat. My oil pressure was running extremely low yesterday on the factory gauge, so I put a mechanical gauge on just like you. It shows hot idle around 30 psi and 50-60psi at cruising speeds. What is an acceptable oil pressure for these engines? I guess my factory gauge/sending unit was lying to me. Is this correct? It read below the middle range and even dipped to the "L" on the gauge. About engine temps... my '98 12v runs best at about 190, I sure would be scared if my temperature climbed above 210 but that is just MHO. Heat is an enemy after a certain point. Thanks

 

I don't remember the PSI, but stock, these engines have low pressure. Usually not a big issue, but leaving the idle slightly above stock is healthy for it and helps keep things happy.

 

Ive driven alot of miles pulling heavy loads (18-20K), if the temp is getting hot or significantly higher with light loads, your radiator may be getting plugged.

When the truck is cold, start it and let the thermostat cycle once then shut the track off and run your hand on the back side of the radiator from top to bottom. If its cooler on the bottom vs top then its plugged. The silicon from the coolant has settled in the lower tubes and creates a gel like blockage. Good news is you can pull the radiator and have it rodded out. Pressure flushing WONT do anything. I have mine rodded every 250-300K.

 

Your 91 is probably the smaller up/down flow radiator. Circulation is bad enuff alone, but would also probably be more suseptible to plugging like mopar2ya said. I modified my core support a bit to take the 93, cross flow, which is bigger too. If I had to do it again, I'd probably look for something in a between sized cross flow from another truck.

 

My manual says minimum oil pressure:
700-800rpm 10psi
full speed 30psi
on the stock gauge idle should be between the L and the first tick about a quarter of the way up and at full speed it should be at about half way up the gauge.

My cooling system works fine on the flats, when you get on the hills with my lead foot i can generate alot of heat. I think an aux tranny cooler would help if you dont already have one since most in this thread seem to have an auto. More heat you can displace before the heat exchanger the better.

 

What ares said on the oil pressure. I know it sounds low but remember that the bearing surfaces in this motor are huge compared to a little gasser.

You don't want the temp gauge going over 210.

 

I would look into a new thermostat with 165. in posts past I mentioned I fried my 93 350 pulling a hilll, perhaps a freak thing?? dont know. I had issues with temps pullinh hills so I started carrying a infared thermo sensor and the day I damaged it I was reading 225 or so on the thermostst housing and 3/4 on the factory guage. I still dont know what happened internally. I think it was a wrist pin, I had same oil pressure. and ran the same pretty much, just knocked pretty bad. My other 250 you cant get it past 5/8, and thats 100 degree day pullin 6k or so.

 

As soon as i start my truck the oil pressure gauge goes right up to H on the gauge. It's been like this since i've bought it. I'm guessing the gauge is screwed up just like the rest of my factory gauges. I'll have to connect a pressure gauge to it to take a look. Has anyone had any problems with high oil pressure ever? Also my fuel gauge is messed up, are they very easy to fix?


thanks

Jeff

 

Thanks for the replies.
Its not running quite as hot now as it did in Alaska. Not sure why exactly, might be the cooler outside temps or I pulled the timing back a bit, now at about 15-16*. Also the new HD torque convertor is probably putting less heat into the rad coolant.

Boy that T/C sure makes a big diference in towing! It was pricy but should be worth it. Picked up a few extra MPGs too.