mobalized

Hopefully someone has the answer to this problem.

I changed a head gasket on my D15B7 roughly 2,000 miles ago and have been noticing issues with my coolant temp ever since. The symptoms are as follows:
The car is slow to warm up at idle, and temperature under load (driving down the highway) is slightly lower than it used to be. Once the car comes up to temperature while driving down the highway (2 bars below half way on the gauge) I stop the vehicle in a parking lot and within 5 minutes the car is 2-3 lines above the cold mark. Once I get going down the highway again the temperature comes right back up. The fans do not kick on, and I have never heard them since I've owned the car which is just over a year. The heat that the blower is putting out IS impacted by this drop in temperature. You would probably think thermostat right? Just changed it this past weekend with a OEM Honda thermostat and the discrepancy did not change at all. I would then think sensors, but I am not able to link how a sensor could cause the irregularity in temperature when I believe that it is all mechanically controlled by the thermostat. Any ideas would be appreciated.

kyden

did you bleed after refilling with coolant?

mobalized

I should have specified, yes it was bled after the head gasket and again after the thermostat.

EsotericImage

iTrader: (8)

was it bled correctly with heat on, parked on incline, sounds like a pump on its way out..


Just making sure im understanding this.. Runs a little warm while driving. Cools down when parked or stopped at idle. sounds like flow issues, so guessing pump

slowDB7

I had this same thing happen to me before, it took me forever to find out what it was

I had a coolant leak that was hidden out of sight check all your hoses and make sure they are tight and sealing completly

mobalized

Please re read initial post car at no point runs warm, always on the cold side after head gasket replacement. It was bled correctly, water pump and timing are less than a year old. No coolant leaks, all lines have been watched very closely, and no fluid has been lost.

mobalized

Also bottom radiator hose never warms up.

slowDB7

yeah i know, i had the same problem the car would take forever to warm up, the temp guage never got as high as it used to and would drop to cold, and the temp of the heat was affected by it too. and would bleed withn no problems.. i finally found a leak small leak at the firewall where the heater hose connects

other then the thermostat whick you already replaced it sounds like you are loosing coolant somewhere, just enough to cause the temp to drop

mobalized

Definitely no loss of coolant, it has been monitored very closely.

mobalized

Bump?

2000EKCoupe

you may have a clog in the heater core. did you pressure test the cooling system? Try a Rad cap too

Vender-

Someone had this same problem; cold bottom rad hose. Go look up that post, apparently his wiring diagram was wrong. Not saying it's the problem; could definitely help with the info on that page. Lmao, i'd give the link but just headin' off to bed. It does exist though.

ArsonistsMind

Make sure the tstat was installed spring side toward motor, your are right in your assumption that the warming up of your cars coolant is dictated by the thermostat only, you may have had some issues with the headgasket install that may be affecting you, usually if it was good before the work was done and its not good after its usually prolly something stupid you overlooked

Hidenplanvew

what brand thermostat?

mobalized

Used two radiator caps both with the same issue. I did not pressure check the system however I would think an obstruction would cause a overheating situation instead wouldn't it?

I will investigate that post.

The thermostat was installed correctly. I do agree that most likely it could have been caused during the head gasket change if the problem didn't already exist in that engine. Its a recently swapped engine so I don't know if its always been that way (I will refer to more specifics below.) It is only something you would notice in cold weather.

The brand is listed in the original post in bold text.

*update- I let the car idle for 15 mins in the driveway with the heat off, the car came up to operating temperature, the lower hose got hot indicating the thermostat is working. I never heard the fan kick on, but I did jump it and it works. I then turned on the heat and the engine temp plummeted. So the heater core seems to be cooling the engine rapidly. Outside air temp was roughly 30 degrees fahrenheit.

strategy400

I have a D15B7 and this is normal. Maybe you just aren't used to it because your headgasket was marginal before causing a slight overheat conditions.
My heater gets colder when there is less load on the engine. This happens at idle or when going downhill. Mine will go almost to the C when going downhill for a few minutes, and I have a thermostat properly installed.
My solution is to turn the heat up a little when it gets colder and down a little when climbing a hill.

mobalized

Must be fairly common then, just don't remember the other b7 doing it. Plus it doesn't seem right and is destroying fuel economy.

kyden

that is not normal at all.

strategy400

It is perfectly normal for an engine to generate less heat when not under a load, particularly downhill with a fully closed throttle (no combustion/injectors off/cold air flowing through).