new radiator in car, still runs hot

[DZink24]

i just replaced a radiator and all coolant in a 1998 dodge neon due to the old radiator being disintegrated beyond repair. after driving the car several miles and getting it up to temp. , and open the hood to check for leaks, i notice that the upper and lower radiator hose are extremely hot to the touch and there is very slight steam coming from the radiator cap. the overflow reservoir is within the limits of normal, and there are no coolant leaks from anywhere. i did not change the thermostat, the one that was in there looked as new as the day it was installed, no corrosion, pitting, deposits. the rubber gasket was even in perfect shape. any ideas what i could do to try and keep the temp. down?? for what its worth, the coolant temp reading on the dash reads right in the middle, like it should, and in the time that i have stood there and watched it idle with the hood open, i've never seen the fan run.

 

[FourBarR]

was it running hot before you changed the rad? If not could be air lock,bad thermostat,fan clutch or sensor, water pump. Thermostat can be checked in boiling water see if it opens all the way. turn heater on full hot,and heater fan. take the rad cap off see if the coolant is
circulating ,which will tell you if the water pump is working. operating the heater will allow coolant to go thru heater and clear air lock. Fan should run if engine is getting hot at idle with little air thru the rad. Hope this helps.

 

[DZink24]

yes, the temp gauge would get all the way into the red when driving, especially in 80+ degree weather and highway speeds. i would need to slow down, and turn the heat on full blast to take some of the heat from the engine. i never saw any steam however, i would occasionally hear coolant bubbling into the overflow container, mostly on the hottest days after a fast drive. almost all the fins were missing, only the "ribs" of the radiator were remaining. i will check the water pump by the technique you described, thank you for the tip. now i wish i would have changed or at least tested the t-stat when i had everything apart, now i am going to have to make a mess with coolant to get it back out.

 

[Hoefler]

I would start with the thermostat, is it in backwards? My be air locked, steam will not open a thermostat. Could be bad, with a new radiator, I would replace it regardless, your talking less than $10. Try running it with out the cap on. Some systems need to be run initially unpressurized to purge the air out. Just some random thoughts off the top of my head.

 

[BGlidewell]

recent spark plug change? spark plugs of the wrong type?

 

[rscurtis]

If the heater produces heat, the water pump is most likely OK. If not, the WP could be the issue. If the pump is OK and the engine heats up at speed, that indicates a coolant flow problem. Put the thermostat in a pot of water on your stove with a thermometer and see how it works as you warm it up.



The fan not running could be another issue, but you shouldn't need the fan at speed.

 

[ata]

1. A hose that has 180 degree water in it is HOT. 2. If the Rad cap is bad it will steam or leak water at temp. Go buy one of those rad caps that has the water temp gauge built in it and then you will know for sure if you have a problem.

 

[B.G. Smith]

i just replaced a radiator and all coolant in a 1998 dodge neon due to the old radiator being disintegrated beyond repair. after driving the car several miles and getting it up to temp. , and open the hood to check for leaks, i notice that the upper and lower radiator hose are extremely hot to the touch and there is very slight steam coming from the radiator cap. the overflow reservoir is within the limits of normal, and there are no coolant leaks from anywhere. i did not change the thermostat, the one that was in there looked as new as the day it was installed, no corrosion, pitting, deposits. the rubber gasket was even in perfect shape. any ideas what i could do to try and keep the temp. down?? for what its worth, the coolant temp reading on the dash reads right in the middle, like it should, and in the time that i have stood there and watched it idle with the hood open, i've never seen the fan run.

The thermostat is probably 190 deg. and you can not tell if it is bad by looking at it. The little power cell that opens it can fail and it still looks new. The fan should run any time the AC in on or when the temp reaches a certain point. If it is in fact overheating the switch that turns the fan on could be bad. If you have access to a hand held pyrometer you could check the temp at the top radiator hose. As stated above the radiator cap could be bad too. bg

 

[GCroyle]

DZinc24,



Also had a Neon with various heat issues, suggest finding root cause ASAP to avoid heat caused cyl head issues.



Lots of good advice already posted, my . 02$ buy an infrared thermometer gun and start shooting at fixed points to get real temp numbers. IIRC ours semed to show hot, never overheated and again IIRC after all gremlins chased or accounted for I changed the sending unit. Car got traded shortly after that.



The IR temp gun will soon be a grab it tool in the tool box, shoot manifold temps looking for missfires, tire temps, AC temps, it goes on and on. Also check those fans, make sure they are capable of being spun by hand (engine off) before computer and engine asks them to spin.

 

[HBarlow]

You didn't provide the odometer reading but the water pump could be worned out.

Sometimes water pumps don't leak, but the impeller is badly worn from corrosion/erosion and simply doesn't move much coolant.

 

[DZink24]

thanks for all the replies so far! off the top of my head, while i am thinking of it, the heater will melt steel, i've never seen a vehicle with such a hot heater, even in single digit temps, this heater blows HOT air within a few miles. i've got approx. 98,000 miles on it, it is a 5 speed with no A/C. that makes me feel good that the water pump is most likely still good. i should have changed the t stat initially, but hindsight is 20/20... i'll go to the auto parts store and pick one up on tuesday, try and change it out w/o loosing too much new coolant or making too big of a mess. i ran it in the driveway today for 15 minutes or so, still did not see the fan run, but did notice that the hoses (up/low), while somewhat hot, were very pressurized, i couldn't squeeze them while the car was running. while the engine was still cold, i ran it with the cap off, and it just looked like the coolant was just sitting there, not flowing. been about 3 years since a spark plug change.

 

[JLEONARD]

I had a water pump where the gear slipped on the shaft and it wasn't pumping water. It was on a VW diesel, but could be a failure mode on any vehicle.

 

[DZink24]

i pulled the t stat today, dropped it in a pot of boiling water, and it opened as it is designed. i put the car back together, ran it a bit, and did actually see the fan running, so thats a plus. . the temp needle on the dash held steady in the mid range, so i will plan on taking it to work tomorrow and see how everything works out. . i am just wondering if there is a bubble or air pocket in the loop somewhere that is causing a problem.

 

[rscurtis]

My sister had a '91 Voyager mini van that had the situation where the temp. guage would go to "hot" before the thermostat would open. The cooling fan would be running but the radiator was cold. Once the thermostat would open, it was fine until the next cold start. What was happening is that it had a slight HG leak that would allow the stat to sit in an air pocket, where it would not open. I drilled a small hole in it to allow the air to pass, and that solved the problem- until the HG finally went all the way.

 

[Hoefler]

You need to check the thermostat by placing it in a pan of water with a thermometer and start heating the water watching to see what temperature the thermostat opens. Just because it opens in boiling water really means nothing. It could be opening at 225* when it is designed to open at 180*.

 

[WalterRyan]

I am surprised nobody has said this yet but it is probably a bad head gasket. This was a problem with the first few years of Neons. They came with a composite head gasket that had a lot of problems. The replacement is an MLS gasket (multi layer steel, like a stack of shims).

I have a 1998 bought new that had the same problem at around 40,000 miles. Wife said it was getting hot, I drove it and it seemed fine. Wife said still gets hot so I took it out and drove a hill at high speed and it got hot. I checked everything in the cooling system and all was good. Did 3 compression checks that looked fine. As a last resort I pulled all the plugs and used a hose with an air fitting attached to my compressor set at 90psi in each cylinder and sure enough when I got to number 3 coolant started blowing out the open radiator. Changed the gasket and It has been fine for another 50,000.

Buy a new intake gasket before you start. They are not supposed to be reused.

I know this is not what you wanted to hear but the job was not that bad.



Walt

 

[DZink24]

i drove it 20 miles today, all expresway speeds, and it was 80+ and humid, and everything went w/o a problem so far. . no leaks, no funny smells, and most importantly, no fires. . (3 very minor engine comp. fires in 4 yrs ) it held temp evenly, and ran pretty well overall.