I have a Civic 1994 LX. I recently replaced all my coolant hoses and radiator. Once I filled the system back up with coolant, I turned on the heater and purged the air bubbles. While I was doing this I checked timing belt and noticed it needed changing. So three weeks later I did the timing belt and water pump and spark plugs and wires/ rotor. This time, I forgot to turn on the heater core when I finished. I was a bit rushed. The engine overheated but I pulled off the car off the road on its own power.

I now have a coolant leak. Nothing I changed appears to be leaking. The car is running better than ever otherwise. The leaking is pretty bad and when I turn on the engine I can see/feel the leaking coming out of the back of the wheel well on the left side and from the sway bar. So I am suspecting a heater core leak, probably due to the overheating and with everything else being new, it had to leak there. Who knows? Maybe it was time to change it anyway and good thing it happened now and not on the road.

I have a road trip planned in nine days.

Here are my questions:

This appears to be a huge job so can I just run a hose temporarily bypassing the heater hoses and heater core for now? Will that coolant flowing through that hose hurt anything? I can't think why it would but I am a newbie.

That should test the theory that the heater core is the cause of the leak. My A/C does not work so I am not worried about that. It also should get me where I am going for the next couple of months and my two or three planned road trips. That was one question but this post is getting long so I will post again when I get ready to do the heater core.

Any other advice will be greatly appreciated.

 

heater core leaks inside the car when bad, not outside. left side of the car as in driver's side, or left side facing it?

 

Thank for the reply, eghatch9295. Driver's side. I was just thinking it may be getting under the carpet and leaking there, but I have not pulled up the carpet. I did get my hands up under the middle of the dash on the drivers side in the area behind the ashtray and behind/below the radio and I fell humidity in there even when the car is not running. The heater hose connections are dry, so is the outside of the oil pump, and all the other connections on the coolant hoses including the AICV/FITV connections. I know water has way of traveling but I see nothing under any of the cooling system parts under the hood, unless it were leaking from the block itself? If you draw an imaginary line at the corner of the rear of the front wheel well where the curved part meets the flat part of the body, across the car or perpendicular to the length of the car, the leak seems to be coming from that area, which seems to be behind the firewall. A puddle forms like a figure 8 with the two main points of the leak being at the corner of the wheel well and another about a foot in. I could pull up the carpet and soundproofing but I was trying to avoid it.

 

heater core is passenger side footwell area. if it was leaking, you'd know. there would be a nice puddle passenger side, and usually a heavily fogged windshield on that side as well.

 

Can you tell us exactly how you sealed the water pump when you installed it? What gaskets and/or sealants you used, and where?

 

Thanks for the tip. It makes perfect sense that it would be more on the passenger side. The carpet on the right side is easier to pull up so I did. It is soaked in there and there is a bluish tinge to the liquid indicating Honda coolant. So it appears to be the heater core, although my windshield never fogged up? I cannot explain why on the exterior it appears to be leaking on the driver's side. It must be finding a way out there because it is not coming from the heater hoses. I wrapped a towel around them and it is still dry!

So assuming it is the heater core, can I bypass it for now? I am in Louisiana so the lack of heat won't kill me.

Again, thank a lot!

 

I used an Aisin water pump. It came with a new gasket. I cleaned the surface/groove where the gasket fits very well, rubbing it with brakleen like 30 times until it felt/looked perfect. I torqued it according to the Helm's, slowly alternating tightening the four bolts. I did not use any permatex or anything like that. This was done about a three weeks ago. Might as well add I replaced both the cam and cranks seals as they both appeared to be leaking. Used OEM parts and did not have problems removing and/or replacing. Valve cover not leaking at all but was before. I could remove the valve cover and top cover of timing belt and inspect but the bottom timing belt housing edges are all dry.

Hope this helps.

 

heater core it is, it happens. I had to replace my sisters heater core twice. the first replacement was with a known good core, second one was new. Yes you can do a bypass to hold you over.

 

Thanks, guys, you all are awesome. Such quick and insightful replies!