91 305 cooling question?

whats the temp range supposed to be? Mine will over around the 190 range for most of a drive and then will climp up to 220... i did have a radiator hose (lower) that had a pin hole that I discovered... the last drive before I discovered that, the temp went above 220 and didnt come back down...  I replaced the lower radiator hose last night and let it idle for 20 minutes in the driveway and it never went over 190.  I went for about a 10 mile drive and it stayed 190 ish the whole time... then right before i got home it went back up to 220, then came down  a tad.  I went out back and had a cigar for it to cool off, and came back out later and pulled the radiator cap off and it was full, the reservoir was in the right range, etc.  When i returned from the road test, the upper hose had pressure in it and was hot....


This morning I drove it to work (35 miles) and for about 30 of those miles, it stayed steady at 180-190 but then at the end it went back to 220 but never went over.. i could see it go back down a bit, so I assume the tstat is opening.... I initially thought a PO had installed a 180 degree thermostat... wouldnt suprise me... cat was removed also...

So where's the correct range and does anyone know why it would have a 30 degree swing but only after being on the highway for a while... its not when I take an exit and slow/decrease airflow. I'm still booking along at 70mph...

I think your ok, that sounds normal. My 91 olds runs about 30-40 degrees cooler, but I think I have a 160 degree t-stat in mine, cause it never goes over 170-180. When you go over 220 that can mean something is starting to fail ( coolant, t-stat, belt, fan). I always try to keep an eye on my gauges, but I don't take their readings as gospel since they are 30+ years old, and they might be the problem. If it happens constant or very often, I would check to see, but if once in a blue moon, nuff said.

Same vehicle and engine in stock condition. Installed 160 thermostat and new temperature sensor and gauge always reads between 160 to 190.

The normal temp range for thermostats is usually stated to be 15-20*F so a 180* would crack at 180 and be full open at 200*. A 193* degree would go from 193-213*.

If you get to full open on a thermostat with all the fans running (if electric), and the temp keeps climbing, it is almost always because the radiator is not keeping up with the heat load. It usually will shop up in high load situations like towing but can be at other times also. That it happens on the highway with the speed giving lots of airflow would be a bad sign for me.

To test, I would go to a cooler thermostat and see if it still goes to 220*. If it does, it is time to look a the radiator capacity or waterpump and lower hose to see if water flow is compromised.

I did a 180 degree t stat and it'll run very cool for a little while but goes right back up to 220 or above after a while. Im going to pull the radiator and replace it... its got a lot of scale built up that i can see from the hose neck and I think its just too clogged and not effecient enough for it to cool well enough and it cant keep up after a while

Anyone have any aftermarket radiators to stay away from? I see them all different prices... its just a stock motor so i dont need anything super heavy duty, other than OE style thats served its purpose for 30 years

Well that was painless …. Replaced the radiator. Now it may run too cool lol. Was fun till I twisted the trans cooler line in two…. Sorta pissed me off but it’s all good now

You should always run the stock temp thermostat. If the coolant temp is not above 195 the computer does not go into closed loop for the best gas mileage.

Always use 2 wrenches when working on fittings. Put some "Freeze-off" on the tube nut a couple of times (and apply liberally) before attempting to turn them.

Fred Kiehl wrote:

You should always run the stock temp thermostat. If the coolant temp is not above 195 the computer does not go into closed loop for the best gas mileage.

Always use 2 wrenches when working on fittings. Put some "Freeze-off" on the tube nut a couple of times (and apply liberally) before attempting to turn them.

YUP. Gonna put the higher one back in now that I've got the cooling issue figured out. I sprayed the lines down before hand, anyway, top one came out fine, bottom one, not so much. it was one with the trans line.

lower ones are always a bigger problem than upper ones, probably because they are more exposed to anything coming off the road