Overheating

[blackeagle113089]

My 94 Q45 has been overheating at random times. I drove it today out to town bout 10miles out and back and it didnt overheat with a/c on. Later on i drove it like 4 miles down the road to blockbuster with the a/c and the needle started to raise im thinkin its the relay for the fan, that turns it on and off, anyone kno where this is located and how much it would cost for a new one?

[Jesda]

Could be a number of things.

When does it get hot? Under acceleration, at idle? How old are the radiator, t-stat, etc?

[Skibane]

Assuming that your drive out to town was on the highway (or at least driven at highway speeds), and your trip to Blockbuster was stop-and-go low-speed driving...

...lack of low-speed airflow (i.e., airflow that is normally supplied by the belt-driven or electric cooling fans) would be a likely culprit.

A problem with the electric fans should be easy to spot - The fans won't be spinning when they should be. However, a bad fan clutch will be a little less obvious.

Fan clutches don't last forever, and tend to fail by gradually allowing more slippage between the engine and fan blade (i.e., fan runs slower and slower, resulting in less and less airflow).

With a good clutch, if you spin the fan blades by hand (after the engine fully warmed up), the blades will stop spinning almost immediately (which indicates a good, tight mechanical connection between the fan and the water pump pulley). If the blades continue to spin for a few revolutions afterwards, the clutch isn't doing its job, and needs to be replaced.

[blackeagle113089]

to town was maybe drivin at bout 50-60, but it only seemed to over heat at idle, not much when driving, it went back down to normal when driving

[maxnix]

I am bettting water pump thermostat. Inspect them.

[bullittandy]

to town was maybe drivin at bout 50-60, but it only seemed to over heat at idle, not much when driving, it went back down to normal when driving

If its a normal temp when moving and gets hot when stopped or at slow speeds then you have an aifflow problem. Like others said, either a bad fan clutch or aux cooling fan not coming on.

[blackeagle113089]

yeah its all stock stuff in the engine i do believe. it only overheats at a stop for long periods. im thinkin thermostat cuz i do hear the radiator fan turn on and it does come on

[xerexabante]

check your fan if it is turning on. let it idle see if it turns on. check your coolant level as well. change your thermostat w/ original only! it makes a difference. do not waste your money w/ cheap ones. if it dies not turno on try to hot wire your fan, if it turns on check you relay, and or your fuse. change relays from different ones that you got, if they are the same color relay they should be the same. you should have one there that is the same.

[Q45tech]

OEM Theremostat fails by not allowing the coolant to warm up ...........failure to open [uverheating] is a very very rare condition the converse [underheating] is common after 3 years.

To me radiators should be replaced every 150k or 10 years............they just cannot function as brand new after that time period.........too much sulfur/ozone/chemicals in the air to avoid external aluminum fin corrosion.

Depends on how close to brand new wants the cooling temperature under stress.