Chip Phillips

Hi, I have a 1994 Honda Civic CX 1.5L with some temperature issues. I have replaced the thermostat 3 times, and flushed the cooling system twice. It doesn't use any coolant at all.
The problem is: When I am on the freeway, during long trips, the temp. will start rising slowly-up hills etc. On my past trip it made it very close to the red. Also, the fan will come on while I am driving down the freeway-I know this because I have pulled right over to check things out and it was on. Also, while I am driving down the freeway and this is happening, if I rev the engine up, the needle seems to kick down a bit. Do you think it could be the temp sending unit? I thought it might be air in the system and have bled it very carefully(let it run with rad cap off until thermostat opened and fan came on). It never has done this in town or in traffic. Also-It is a freshly rebuilt engine, with a new water pump. I blew a head gasket after about 6k miles, but that is fixed and everything is working well in that area(no bubbles in coolant, etc.) Any help with this would be really appreciated. Thanks, Chip

Inliner

sounds like a bad head, either warped or cracked or coolant hoses misrouted.

Chip Phillips

Thanks for the response Inliner. I just had the head gasket replaced and the machine shop checked the head out-said it was fine. I am kind of surprised that the gasket blew after only 9000 miles or so though. Coolant hoses are correctly routed as well.

TravisCadello

my friends car does a similer problem. his is a 2000 civic ex 1.6 if it idles more than 10 minutes it goes all the way to the red and sits their untill he drives it or revs it up then its fine. and on long trips on the highway we have to punch it alot or if it sits at a steady rpm it over heats. we took out the thermostat a long time ago it never fixed it.

94EG8

I can't say the same. I've seen more D15B7s and D15B8s repeatedly blow headgaskets then I can count. I have yet to see one last more than a year after replacing a headgasket, and i've seen a couple go through 5! at which point the engine was junked in both cases.

The_Honda_Guy

Have you actually tested the coolant temp sensor to make sure it is reading correctly?

Chip Phillips

No, I have not. How do you do that?
I did replace the rad. today-$94 at Napa. I won't be able to tell if this has fixed it until I take it on an extended trip though. If it was the temp sensor, would'nt it act up most or all of the time, not just on the freeway during extended trips?

The_Honda_Guy

The temp sensor can be checked using a multimeter and doing a resistance test. You'd be best to purchase a Hayne's manual, that way you'd have the specs you need to test it among other things. Sensors can act up at really any time, it's not always a set thing.

Anon51

did you replace the water pump when you replaced the headgasket?

Chip Phillips

The water pump was replaced when the engine was rebuilt-about 12K miles or so ago. It isn't leaking or making any funny noises. There is a subtle whirring noise but I'm pretty sure it's the alternator-I think it has always sounded that way.

nissan480

1993 cx eg,head gasket change at 155k,now has 19?k with no issue's!New head bolts,head resurfaced and cleaned,intake and exh mani gaskets and thermostat were changed