I have a 98 honda civic ex, I recently had a bad coolant leak due to my heater core being so bad the coolant would leak all over the ground underneath the core area, I haven't replaced the heater core yet but did have the heater hoses bypassed till I have the funds to replace the actual core.

The problem is ever since the heater hoses were bypassed i noticed the coolant level drops in the radiator but the reservoir stays full due to it not returning any coolant back to the radiator in fact the reservoir level is higher than the max line right now, so I find myself topping off the radiator daily.

I tried replacing the radiator cap but nothing.

I started the car with the radiator cap off and thought all the air bubbles got out but maybe there is still air in the system.

All hoses get hot and can't find any coolant leaks under the whole underhood area but do still see alittle coolant under the heater core area which puzzles me since the heater hoses are bypassed so no coolant can reach the core anymore.

I know a bad head gasket can cause this to but i don't have any signs of the head being bad, no white smoke coming from the tailpipe, no coolant mixing with the oil, transmission fluid.

I'm a girl but do know some things about cars but this problem has me puzzled. Thanks for reading

 

The coolant has to be going somewhere. You can rent/buy a block tester kit and compression tester to rule out an internal issue.

 

Thanks will have to get those tester kits . Was thinking the radiator coolant was just going to the reservoir tank since the tank coolant is just about to the top of the bottle now but could be wrong. Will test for a internal leak

 

Seems like with these cars those signs you mentioned rarely show up. Coolant loss from radiator that ends up in overflow tank is usually the strongest symptom of a head gasket leak. Follow what eghatch9295 said. If you get lucky maybe a new radiator cap will solve the issue.

Did the engine ever overheat at any time?

 

Hi the engine has come close to overheating when i had a bad heater core leak I never let it reach the red line when it started overheating. I ordered a block tester just waiting for it to come hoping it's not gonna end up being the head gasket

 

Also pressure test the cooling system.

 

/\ yes. especially if the block and compression tests come out ok.

 

Okay thanks guys will pressure test the system if the other tests come back fine

 

Okay I'm still trying to find the problem. I do know it's not due to the head gasket had the car tested a few times had nothing but negative results. I had a leak in the coolant tank so replaced that and thou it fixed the problem since coolant was going to the radiator but after a few days it stopped again I tried 3 different radiator caps still the same.

I just had the car running for a half hour with the hood open and radiator fan does come on, I did notice that both radiator hoses get equally hot ( really hot )to the touch, it's my understanding that the bottom hose shouldn't get as hot as the top hose unless I'm wrong with that also the radiator cap never got hot to the touch in the half hour it stayed warm , I do recall my old cap getting hot to the touch and also sounds like a hissing sound coming from the front passenger side by where the whole cooling area is, didn't see coolant dripping anywhere so not sure what the problem is but it's driving me crazy.

Any thoughts - starting to question the radiator and thermostat

 

Sounds like you need to properly bleed the cooling system.

https://honda-tech.com/honda-civic-d.../#post39830585

 

thanks Ron, is there a way to properly bleed it without having to turn on the heat.? Only asking because I have no heat in the car haven't had the heater core put in yet and have the heater hoses bypassed at the moment

 

The reason you turn on the heat is to remove any air from the heater core. Since your's is bypassed and doesn't have a heater core, then it may be a moot point.

Your bypass hose, is it after the heater coolant valve, looping it back on itself, if it is, then you still should put your heat to max as it opens this valve and lets the coolant (and air) flow back through the system to the radiator.