CptHMCrunch

H22A is currently losing coolant. I do not think it is a head gasket leak. Motor was rebuilt. Rod bearings, rings, valve job, stem seals, new head gasket, etc. Motor has ~700 miles after rebuild. The motor passed leak down with ~9% on each cylinder after first cool/warm cycle following rebuild. No rise in coolant level or bubbling with leak down. Vehicle needs a very slight topping off each day. All coolant hoses have been replaced. Here is information

1. Engine loses small amount of coolant each day.

2. The overflow tank NEVER receives coolant from the cooling system. If the overflow tank is at the minimum line, it will remain at the minimum line under ALL driving conditions and through all normal operating temperatures.

3. Radiator caps is new.

4. Upper radiator hose can be squeezed ~1/2 way closed at full operating temperature. Pressure in upper radiator hose feels about right.

5. Thermostat is functional by visual observation of change in coolant flow during warm up cycle.

6. Water pump is new and functional.

7. Vehicle does not overheat.

8. Inspection has been done at all hose clamp locations by feeling for coolant and/or scaling deposits from evaporating coolant. Possible leakage found.

9. Inspection has been done at both ends of water pipe for leakage.

10. Inspected line from radiator to overflow tank for cracks, found nothing.

I am beginning to suspect that there is a pinhole leak in the radiator, blow by at one of the hose clamps, or leakage at a rubber o-ring style gasket somewhere. I do not suspect a blown head gasket because it is brand new, I have never failed to successfully replace a head gasket, the coolant system is not being pressurized, and the overflow receives no coolant. The vehicle is currently going through a slight warm/cool cycle with cardboard under it. All hoses were thoroughly wiped clean and will be reinspected after the cool down.

Has anyone experienced coolant loss with similar symptoms or under similar circumstances? Any input would be greatly appreciated.

94CivicSi

iTrader: (1)

Have you checked for damp carpet and/or padding inside the car, down underneath the dash? Could be heater core.

I would say no to an external leak. In my experience, even little ones are obvious, and it sounds like you're looking very carefully.

CptHMCrunch

Most of these observations were made before there was any alarming notice of missing coolant. I did notice that some coolant was missing after the first day of running but I figured that it was just residual air that had worked its way to the top of the radiator but had not be expelled through radiator cap. Unfortunately I had to move half way across the country for school the day after getting the car on the road, so I was not the person doing the inspection for leakage. My girlfriend was doing inspection for leakage as I instructed her over the phone.

I had a garage pressure test it and they found that the OEM style hose clamp was allowing the lower radiator hose to leak coolant while pressurized. This was the spot that I suspected to be leaking as I had previously noticed a small drop of coolant clinging to that location. I wiped it dry and chalked it up to residual coolant dripping from the refill. My girlfriend indicated that the same location put a small blotch of coolant on a clean rag. The shop said they put another hose clamp on it and it now holds pressure.

Also, a heater core leak is an external leak because it allows coolant to escape to atmosphere.