Hot Gauge, cold engine, low coolant + air

[ElectricSunset]

Hi,

 

I have 1997 Legacy Brighton 2.2 (not the 2.5 with gasket issues) with 83K.

 

Recently the Temp Gauge showed Hot while driving on the street. Pulled over. No steam, engine warm (not hot), radiator warm/cool, coolant tank low,coolant fan not working. There were a few drops of coolant next to radiator cap. When open rad cap heard swoosh of air. Later thermostat checked out and no leaks. Had at least 4.5 quarts of coolant in system when this happened. Was obviously low on coolant and air in system. After flushing coolant and burping system it does not get hot and COOLANT FAN WORKS! I'm thinking that the coolant fan did not go on because the engine was not hot enough. CAN AIR IN THE SYSTEM CAUSE A TEMP GAUGE TO SHOW HOT WHEN THE ENGINE IS NOT HOT? How do I know if I damaged the head gasket or engine?

 

thanks

[nipper]

Yes. Coolant fans need a hot radiator to work No water in the system, the radiator never got hot, fans didnt need to come on. The temp sesnor is in the engine block. Low wtaer your engine was running hot. Water carries the heat to the radiator and is the final link in this chain.

 

 

 

nipper

[porcupine73]

Hi ElectricSunset and welcome. Yes, air in the system can cause the temp gauge to show hot when the engine doesn't seem hot. The coolant temp sensors are in the coolant pipe near the top of the engine. Typically this is an area where air in the system may rise into. Depending on how much air you have in there, it can get very hot as it contacts the heads, etc.

 

Replace radiator cap. It isn't that expensive and these do build up gunk under the parts in the top and it doesn't seal correctly sometimes. Make sure radiator neck where the cap goes on is clean.

 

For a few trips when the engine is cold, try checking the coolant level before each trip by removing the radiator cap. If there is any leakage anywhere in the system, the vehicle can't pull coolant from the overflow tank back into the system.

 

Also it can be somewhat easy if you're not careful to trap air in these systems. There are many posts on here about how to refill the coolant and get the air pockets out. If the coolant was changed not too long before this hot temp gauge issue, it could be air pocket in system.

 

Oh yah, if there is exhaust blowing into the coolant this could happen too.

[johnceggleston]

my radiator cap leaked only after the engine reached operating temp. i never would have seen it (and we all know what overheating does to a 97 - 2.5L engine), i never would have seen it if i hgadn't let it idlw in the drive way for a while.

so if you want to check your cap / cooling system, get it up to operating temp and let it run in your driveway. my leak was hard to see at the cap, it trickled down the side of the rad and dripped of.

 

a new cap fixed it.