Hi, I have a 1995 Honda Civic Ex and it began to overheat driving down the interstate at 70 mph. It only overheats when sustained rpms over 2500...therefore driving 50 or 60 mph the temp gauge is completely normal. I have change the thermostat and flushed the radiator. I am losing radiator fluid but not experiencing any white smoke, rough running, and the oil from the dipstick seems pretty normal. Will I need to drain oil from the pan to check for milkiness? There is no fluid or sign of fluid in the spark plugs. There does seem to be a leak coming from under the timing belt cover. Will the weep holes from the water pump "weep" enough to show a visible leak? No extra fluid has been noticed in the overflow...sound like a bad water pump...bad head gasket...? Any help out there?

 

sounds like a water pump.
i would ask if the fan works but on the highway you wouldnt really overheat with or without a fan

 

Hi all. First post. . .anyway.

I am going to presume you are running the D16. That being the case, my 94 did the same thing to me. As it turned out mine was a head gasket leaking between the cylinder and water jacket. I understand you said no white smoke, mine did not either. . .not until it began to get worse.

Initially I could smell antifreeze. I put UV dye in the system and was up and down everything under the hood looking for dye and nothing. So I let it go and every couple weeks when it would rev up and down when cold, I would add more antifreeze. This eventually turned into an every other day task. This was my daily driver so it wasn't abused, boosted, modded or anything. Just a bone stock 220K mile D16z6. OK, so maybe it was in the vtec range several times a week. I figure that just ensures I keep a constant supply of fresh oil added between changes. LOL

Occasionally when I stated it, would would billow out a decent white cloud with that ever notable sweet stench of ethylene glycol. YUCK. Then I pulled the head, changed the gasket, timing belt and water pump. Still going strong at 250ishK miles.