Smart decided to add a drain plug to the 451 to save us from having to suck oil out through the dipstick tube. Of course, that lead to more problems, way worse than having to buy a vacuum oil pump.
Firstly is the least problematic. The mess. You can never quite correctly gauge where to put the container to catch the old oil so you can guarantee an overshoot.
The 2nd issue is people’s insistence on over tightening the drain plug which eventually strips the threads in the aluminium sump. The drain doesn’t tighten, the oil escapes and that leads to a new sump.
The final issue is the worst one and this issue is starting to appear far more regularly now. The aluminium sump actually splits when you fit or remove the sump plug. It’s possibly down to the heat cycling, corrosion and stress from removal and refitting of the drain plug. Why it does it is in contention but if it does crack, you get a sudden loss of oil and you have to fit a new sump.
No 451 aluminium sump has ever cracked during driving that I have heard of. They crack during the removal or refitting of the sump plug.
It should be noted that fitting a new sump is a terrible job as pipes and things actually bolt to it down the back of the engine! It’s an engine lowering job.
So, there are 2 sensible options. Either get an oil vacuum pump and suck the oil out of the dip tick tube or fit a check valve drain plug.
This drain plug replaces the original and contains a ball bearing check valve that only opens when you push the drain tube into it. The drain tube comes with a short length of flexible pipe that you can place into the collection container before connecting the drain tube to the check valve.
No more mess and no more removing and refitting the drain plug. No more new sump washers and no worries about stripping the threads or cracking the sump pan.
The A2 stainless steel check valve drain plug comes with a protective cap to keep the check valve clean when not being used.
I personally have been testing one on my car since 2013 and after 4 years with no problems, I’m happy to sell them.
These will only fit the petrol models of the 451.