Cracked Head - does this sound right?

[Gambor]

My car now has a second hand VS engine fitted (140,000km) and it seems to run very well.

But from the first day I got the car back from the mechanic, I find the car has leaked a small amount of coolant when I check in the morning (50-100ml?), dripping from the sump. This only happens overnight, in my garage (which has a 20% slope, car is usually nose higher than tail, but I tried reverse parking in overnight, and it still happened)

However when I leave my car anywhere else, it does not leak coolant at all, though that has been entirely during the day. ie on short trips, in carparks - no leak. 10 hours on the flat driveway during the day - no leak. Work carpark for 8-9 hours, no leak.

I would like advice on where the leak could possibly be coming from (or why it only happens in my garage at night - maybe when something in the car cools and shrinks, a leak is opened?)

The car has had extensive repairs and new parts installed in the last four months. As below:

Late June 2011
- Drive Belt Micro
- Pulley Belt Tensioner
- Pulley - Upper
- Pulley Idler
- Power Steering Pump
- Balancer - Harmonic
- Power Steering Hose
(replaced power steering pump assy, low pressure line, main drive belt and pulley's, bleed power steering system and carry out road test)

Late September 2011
- Tens Assy - Belt
- Drive Belt Micro
- Coolant Flush/Fresh Coolant

Late November 2011
- Replacement Second-hand Engine (VS, 140,000km)
- Water Pump
- Thermostat Radiator
- Thermostat Gasket
- Oil Filter
- C/Set Commodore
- Semi-Synthetic Engine Oil
- Coolant Flush/Fresh Coolant
(removed and replaced complete motor. Replaced water pump, rear cover gasket kit, seals, some coolant hoses, spark plugs, engine oil and oil filter and repair exhaust studs on the exhaust manifold)

Obviously this has all cost a bomb the last few months. But most components under the bonnet look gleaming and new, or very well cleaned/looked after. The mechanic mentioned he had a coolant leak after he fitted the engine, and had to pull the engine out again to replace a gasket of some kind (manifold gasket?) - it was a large metallish thing, about two fists in size.

Considering how much of my car under the bonnet is new and how much work has been put into it, I am very concerned about the coolant leak even if its very low volume. Does anyone have any idea what it could possibly be?

 

[GTS69]

man take it back to the mechanic and tell him to fix it he shouldnt charge you could be something simple like a lose clamp or pinched hose to the over flow been over full and when it pushes water back to the over flow its spilling over could also be the water pump adn running down the block and dripping off the sump you should be able to pop the hood when you get home and keep a eye out for where it looks to be coming from it may also make a sound you can trace good luck