Problem starting

Even with the keys out , the radiator fan will run for a while if needed to cool engine .Perfectly normal . You checked your coolant level?

yes coolant is fine, its the starting and restarting of the car thats doing my head in

Maybe an issue with the coolant temp sensor if the fan is running at full speed,advise you get the codes checked.

Could be a faulty crankshaft sensor .

The problem with your car is a slow turning starter! An under powered starter will start a cold engine much easier than a warm one. Ive seen and solved this problem with your symptoms many times. It may not sound to be turning particularly slow but trust me, compared to a new one its a snail! Ur car will be a 2.0DTI? Very common fault ive found on vauxhalls with that engine. Aftermarket motor £80 with ur old one back. Not a big job to change for the right man. 2-3 hours.

Nothing in post to assume starter turning slow.Poster does not say what engine .A faulty starter will be under more load on cold starting , not hot .Dont know where you get your 2-3 hrs to change starter from .Time to change starter ,1.8 petrol- 54 mins ,2.0d -66 mins, 2.2 petrol 70 mins .Not a big job whatever engine , if needed .

Think you are looking at a Tempreature sensor issue there,s two of said sensor,s that sit in a plastic housing ,which also houses the thermostat, as the fan motor is controlled by the e.c.m .and it can only function on what values it is seeing from these sensor,s.The fan motor will run full speed when starting from cold and like you have said run,s full on when car is switched off,but can be reset by briefly switching ignition on/off. Have had this issue on two car,s now ,This can drain your battery level .causing none start.The complete housing requires replacing any one competent could change it in half an hour.

hot engine higher compression.

An engine’s compression ratio is calculated by taking the total swept volume (with the piston at bottom dead center) and dividing it by the total compressed volume (with the piston at top dead center).This will not alter with temp .

starting a cold engine is equivalent to performing a dry compression test. Because the rings have not formed their seal properly you will find a lower compression reading. The wet test is the equivalent of a hot engine... higher compression. A weak starter will start a cold engine easier than a hot engine.

A wet test merely indicates whether there is piston ring and/or cylinder and piston wear.Using your theory all cars would be low on compression on cold start which is not the case .Any problematic cars we had on starting were left overnight and started from cold when the load was greatest .If you disagree , you are entitled to your opinion. I also asked a couple of other garage owners who I walk my dog with for their opinion in case I was missing something , but they were of the same mind as myself .We will have to agree to disagree but that's what forums are about .

thats fine with me. i dont agree there is more load from cold on a starter motor. i am however talking from hands on experience like i said at the beginning of this thread. The fix i suggested works for me going on the symptoms described. The car may have an unrelated problem hard to know these things unless the car in front of you, but we'll agree to disagree. On good cylinders when carrying out compression tests from cold you will still get a higher wet test value.

Having spent my entire working life in the motor trade , covering 45 yrs + starting as a mechanic , foreman , service manager , general manager with different franchises and running my own premises , I also am speaking from many , many years of hands on experience .But interesting to hear your theories and possible help with other questions .Best wishes .

Sorry if i caused offence was unintended. Best wishes

No offence taken , your help is always welcome .As you say ,it's hard to fix cars from a keyboard .If we could , we would all be rich without getting our hands dirty or leaving the house .