I've noticed as soon as i start my car the cooling fans immediately start running and they don't shut off, the car obviously isn't hot and i don't have ac or heat turned on but they still come on, i have a code for thermostat open would this cause them to come on or is it something else causing this? i don't have a code for anything else that is related to this, anyone have a fix for this before i take it to the shop?
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fans running constantly
- Thread starter jsproule
- Start date
I just had this issue and replacing the thermostat returned the fans to normal operation.
You may also want to consider flushing your coolant, making sure to disconnect every possible hose to check for sludge. If sludge is present, Prestone Radiator 2 in 1 Flush and Oil Degreaser helps. Following that up with Prestone AS105 Radiator Flush and Cleaner helps to get out residual deposits. Thoroughly rinse flushing after each treatment until water stays clear is recommended.
You'll need to jack your front end up to remove under-shielding and access radiator drain plug.
Hopefully your head gasket isn't starting to leak. Inspecting spark plug condition can be telling. What also helps in determining this is Block Tester BT-500 Combustion Leak Test Kit. It's relatively simple to use:
- Flush system
- Add water, burping system until reservoir is only 1/4 full
- Shut engine off
- Prepare test kit
- Warm engine with radiator cap off
- Place kit tube tightly in reservoir before water level rises (hand pump not required)
- Should see bubbles rise up in test fluid as coolant/water rises
- Remove tube before before coolant/water level reaches tube (will contaminate test)
- Quickly shut engine off
- Once coolant/water level is back down to quarter, repeat
- Do at least 10 times, continually comparing test tube fluid color with fluid in kit bottle
Even the slightest change in color could be a positive indicator. You may need to run multiple tests as well for consistency. If it is positive (yellow) more often than not, you could bring to a shop for further and more conclusive diagnosing before making any significant decisions like replacing the head gasket (which may not be viable for these engines, since the bottom ends may begin to fail under the increased pressure load, especially if coolant was getting into the oil, which I was told weakens the piston rod bearings - either oil gets into the coolant (sludge), or coolant into oil (chocolate milk), or both, depending on severity and location of leak).
Replacing the head gasket also requires diagnosing and reconditioning of head at a machine shop, where it is checked for cracks and resurfaced for flatness (otherwise a new gasket will leak from imperceivable warping). There is also the risk of cracks in the block, which a replaced head gasket will not fix. If this engine wasn't so poorly engineered then a head gasket replacement wouldn't be as much of a risk, and probably wouldn't fail so early and often to begin with (the '96 Integra I bought at 140K drove strong up until I sold it running at 200K without any head gasket, coolant, or overheating issues. In fact, the thermostat failed in an opened position, only preventing the engine from reaching operating temperature, especially in cooler conditions, which is far safer than what you have going on here, which will eventually lead to overheating, so keep an eye out for your temperature light and pull over immediately if it comes on).
You may also want to consider flushing your coolant, making sure to disconnect every possible hose to check for sludge. If sludge is present, Prestone Radiator 2 in 1 Flush and Oil Degreaser helps. Following that up with Prestone AS105 Radiator Flush and Cleaner helps to get out residual deposits. Thoroughly rinse flushing after each treatment until water stays clear is recommended.
You'll need to jack your front end up to remove under-shielding and access radiator drain plug.
Hopefully your head gasket isn't starting to leak. Inspecting spark plug condition can be telling. What also helps in determining this is Block Tester BT-500 Combustion Leak Test Kit. It's relatively simple to use:
- Flush system
- Add water, burping system until reservoir is only 1/4 full
- Shut engine off
- Prepare test kit
- Warm engine with radiator cap off
- Place kit tube tightly in reservoir before water level rises (hand pump not required)
- Should see bubbles rise up in test fluid as coolant/water rises
- Remove tube before before coolant/water level reaches tube (will contaminate test)
- Quickly shut engine off
- Once coolant/water level is back down to quarter, repeat
- Do at least 10 times, continually comparing test tube fluid color with fluid in kit bottle
Even the slightest change in color could be a positive indicator. You may need to run multiple tests as well for consistency. If it is positive (yellow) more often than not, you could bring to a shop for further and more conclusive diagnosing before making any significant decisions like replacing the head gasket (which may not be viable for these engines, since the bottom ends may begin to fail under the increased pressure load, especially if coolant was getting into the oil, which I was told weakens the piston rod bearings - either oil gets into the coolant (sludge), or coolant into oil (chocolate milk), or both, depending on severity and location of leak).
Replacing the head gasket also requires diagnosing and reconditioning of head at a machine shop, where it is checked for cracks and resurfaced for flatness (otherwise a new gasket will leak from imperceivable warping). There is also the risk of cracks in the block, which a replaced head gasket will not fix. If this engine wasn't so poorly engineered then a head gasket replacement wouldn't be as much of a risk, and probably wouldn't fail so early and often to begin with (the '96 Integra I bought at 140K drove strong up until I sold it running at 200K without any head gasket, coolant, or overheating issues. In fact, the thermostat failed in an opened position, only preventing the engine from reaching operating temperature, especially in cooler conditions, which is far safer than what you have going on here, which will eventually lead to overheating, so keep an eye out for your temperature light and pull over immediately if it comes on).
Last edited:
Thank you so much! Don’t think there’s any problems with head gasket it was replaced already definitely will replace the thermostat and hope it fixes it,thanks for the coolant tip too!I just had this issue and replacing the thermostat returned the fans to normal operation.
You may also want to consider flushing your coolant, making sure to disconnect every possible hose to check for sludge. If sludge is present, Prestone Radiator 2 in 1 Flush and Oil Degreaser helps. I like to follow that up with Prestone AS105 Radiator Flush and Cleaner (rinse flushing between the two treatments).
You'll need to jack your front end up and remove under-shielding to access radiator drain plug.
Hopefully your head gasket isn't starting to leak. A You may also want to check your spark plugs, as their condition can be telling. What also helps in determining this is Block Tester BT-500 Combustion Leak Test Kit. It's relatively simple to use:
- Flush system
- Add water, burping system until reservoir is only 1/4 full
- Shut engine off
- Prepare test kit
- Warm engine with radiator cap off
- Place kit tube tightly in reservoir before water level rises (hand pump not required)
- Should see bubbles rise up in test fluid as coolant/water rises
- Remove tube before before coolant/water level reaches tube (will contaminate test)
- Quickly shut engine off
- Once coolant/water level is back down to quarter, repeat
- Do at least 10 times, continually comparing test tube fluid color with fluid in kit bottle
Even the slightest change in color could be a positive indicator. You may need to run multiple tests as well for consistency. If it is positive (yellow) more often than not, you could bring to a shop for further diagnosing before making any significant decisions like a head gasket replacement (which may not be viable for these engines, since the bottom ends by begin to fail under the increased pressure load, especially if coolant was getting into the oil, which I was told weakens the piston rod bearings - you can either have oil in coolant (sludge), coolant in oil (chocolate milk), or both, depending on severity and location of leak).
Replacing head gasket also requires diagnosing and reconditioning of head at a machine shop, where they check for cracks and resurface mating area for flatness (otherwise new seal will leak from imperceivable warping). There is also the risk of cracks in the block, which a replaced head gasket will not fix. If this engine wasn't so poorly engineered then a head gasket replacement wouldn't be as much of a risk, and probably wouldn't fail so early and often to begin with (the '96 Integra I bought with 140K drove strong up until I sold it running at 200K without any head gasket, coolant, or overheating issues. In fact, the thermostat failed in an opened position, only preventing the engine from reaching operating temperature, especially in cooler conditions, which is far safer than what you have going on here, which will eventually lead to overheating, so keep an eye out for your temperature light and pull over immediately if it comes on).
Glad to help.Thank you so much! Don’t think there’s any problems with head gasket it was replaced already definitely will replace the thermostat and hope it fixes it,thanks for the coolant tip too!
Should definitely do combustion test to verify that the head gasket repair was successful, since it's not guaranteed to be (it's not a trivial job).