I have a opel zafira 2008 it has oil leaking into the coolant bottle but I had a compression test done and it came back fine so what else could it be
Oil cooler leak. There is oil cooler behind catalyc converter,where oil is cooled by coolant in little box. Seals needs change.
Type zafira b oil cooler on ebay.
If you have oil leaking into the coolant, then the head gasket has gone bad.
You can confirm this by driving down the road when your engine has cooled down, turn the heat on low and listen for a gurgling sound, like there's air in the water somewhere. It's a clear indication that air is leaking into your coolant from the chamber and going through your heater core. It may be why your hot air isn't so hot anymore
It may be too small to notice with a compression test, or it could of just been a complacent mechanic that seen 1-3 cylinders good and one was off by just a hair, but it'll be alright, it may only happen once you drive down the road when the vehicle isn't at idle RPMs.
Changing a head gasket is fairly easy, but it's around a 10 hour job, sometimes it may even require removing the motor from the engine. Here's a rough outlook that may not be specific to your type of car, but it gives you a general idea:
Disconnect the negative battery cable
Drain the cooling system (coolant)
Remove the Intake manifold
Remove the throttle body
Remove the PCV valve
Remove the air filter
Remove the alternator
Remove the spark plug wires
Remove the spark Plugs
Remove the Distributor cap ( or coil pack )
Remove the radiator fan
Remove the coolant pump
Relieve the fuel pressure ( pull the relay in the junction box and start the car 3 times )
Remove the fuel line
Remove the fuel injectors
Remove the exhaust manifolds
Remove the head cover
Remove the timing chain ( Mark chain to sprocket with a ink pen )
Remove the timing chain Tensioner
Remove the head bolts In a random order when the engine Is cold ( Failure to do so when the engine is cold may result in a warped head )
Remove each head bolt by 1/4 of a turn before removing ( New head bolts required on Installation )
Use a pry bar at the corners of the Cylinder head-to-engine block ( Do not pry between the cylinder head and the engine )
When Installing place the engine at Top Dead center, by aligning the notch in the crankshaft pulley with the TDC Indicator
When Installing - Inspect all hoses and replace all gaskets
When Installing - tighten head bolts in s specific sequence such as this
Other symptoms of a blow head gasket
I don't mean to scare you, but since it has gotten cold the seal has contracted a bit making an opening for a passage way into your coolant, (it may only happen when you step on the gas) If you stick it out until summer the seal may expand and fill the gap... a leak such as these can cause a engine block to crack because water (coolant) is getting into the combustion where it uses oil to dissipate the heat and lubricate the parts, water and coolant cause corrosion.
But before you go spending 1000 dollars on a mechanic or 50-300 dollars on a bunch of new gaskets, keep in mind that they also make stop leak formulas for the oil for small head gasket leaks.
It's a head gasket, but make sure the heads get cleaned up from all of the carbon when it's changed, no reason for that to go undone. It gets rid of any knocking noise and makes your engine happy overall.