Hi, My son has a '03 Malibu that seems to be losing coolant but only when it's parked on an incline. We just recently had both upper and lower manifold seals replaced (9 months ago) and all has been fine until just recently. I thought it may be a hose or something, but it dosen't seem to leak unless he's parked on an incline and a hose would leak regardless of how you're parked.

Any ideas? Thanks

 

Could have a head gasket ready to blow. They are common around # 1 and #2 cylinders. Check the spark plugs for rust on the outside and compare then to the others. It could be leak externally and not into the oil or combustion chamber. Another thing with the manifold gaskets. I have had several brought to me that had been replaced recently and they had to be replaced again. Its kind of a touchy job and the lower manifold gaskets have to be torqued exactly as instructed, in the proper order. Vertical bolts first.