Hello,

I’m a new user on this forum, and have a 2004 Civic 4-door EX. In late November I had my timing belt and water pump replaced at 112,000 miles. The belt was slapping the plastic cover from time to time. After the replacement, the engine seems to run much smoother and sounds great now. However, I’ve notice that the heater does not warm the car at idle any more, only when I have the RPMs up some. The engine temperature gage seems to register in the same general location as before the belt change.

Is there a chance a thermostat regulator was not reconnected, an air bubble in the core, etc. The coolant reservoir is at the high side of full. Can someone give me some ideas to check out? The work was done by a general garage that we have used several times for recent Honda work, they are good mechanics. I would like to know more regarding what could be wrong before I go back and have them look at it.

The dealer we bought the car from and used for all work in the past 8 or 9 years has begun hammering us on costs, so I’m looking for cheaper ways to maintain this for the next 100K miles. Any insight or ideas will be welcomed.

Thanks, Joe

 

Probably just an air bubble. You should try purging the system:

Park the car on level ground or facing uphill, so the radiator is the highest point. Wait until the engine is COLD.

Remove the radiator cap (not the white plastic reservoir tank, the actual radiator). The radiator should be completely full to the top. If not, add pre-mixed coolant until full to the top.

Start the engine with the cap off. Set the heater dial to full hot.

Watch the radiator and add more as needed to stay full to the top. Rev the engine occasionally to circulate the coolant(*).

As the engine warms up, the radiator should start to overflow. Put the cap on then. Make sure there is coolant in the plastic tank up to the min line.

Test drive until fully warmed up. Park again and wait until engine is cold. Check the radiator and repeat the procedure if necessary.

(*) If a bunch of coolant and bubbles blow out of the radiator when you rev the engine, the head gasket is probably blown.

 

Thanks mk378! I appreciate the procedure / instructions. Will do this as soon as possible. The engine seems to run fine, so a blown head gasket should not be likely. Thanks for the heads up on the possibility, and for what to look for just in case. Thanks again, Joe

 

Morning mk378,

I tried the system purging process you gave me yesterday. The heater performance have been a little better this morning, but it was also about 25 degrees warmer today than the 3 prior mornings.

Here is what I did: I let the car sit for about 45 minutes after the drive home. (the car was on a small incline, front up) When opening the cap, a small rush of air and or fluid came out. The fluid was up to the top. I started the engine and let it idle for about 10 minutes, with no bubbles coming up. I rev’d the engine to ~ 2500rpms and a little fluid rushed out, the level was down ~1/2 inch after. I filled it and then ran the engine steady at ~2000rpms for another 10 minutes with no bubbles seen either. I let the car cool for 1 and ½ hours, the fluid was down 2 inches. I filled it and repeated the 2000 RPMs run for another 10 minutes; no bubbles were seen this time either. The fluid level stayed steady all the time with the one exception noted above.

I’ll give this a try again this weekend with the car sitting out all night first.
If there appears to be any problems with what I did, please let me know. Thanks again!