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Rainbow coloured trail of liquid (substance ) from behind or around car, only see it in the rain. What is it please ?

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Whenever it rains I always seem to notice a trail of multi colured ( rainbow like) liquid usually as a trial from behind my car or wherever the car has driven. I never see it in the dry conditions, only when it has been raining



Somebody said it could be oil or fuel.

I do not think it is oil, My car has a slight oil leak which is from turbo oil feed pipe and I can see black oil on the ground.


However, I have had leaking fuel injectors in the past, the seal was replaced on one injector, on the other he simply glued it back in (which is stupid imo)

My car often chugs too, only at idle mostly, and once full operating temp is reached the noise goes away.


any ideas ?



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2 minutes ago, stef123 said:

The rainbow affect is definitely from oil or fuel.

you can see black oil on the ground? Well that's why your getting a rainbow.



I can only see one drop of oil under my car once every few minutes. not sure if this is the cause for the rainbow substance or if it is fuel related as I suspect it could be an injector fault. they have been leaking in the past and I recently saw a photo on my phone that I took last time to read codes from a laptop from last diagnostic test, it reads fuel injector mallfunction. however that could be from last time they were leaking and maybe code has not been rest por has been reset afrer I took photo, will have to ask friend to plug his laptop back in.


car chugs as well which I guess could be injector related

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If it looks like this then it's oil or fuel. 

You do really need to get it fixed. Might not be doing your car much harm just now, but spillages of fuel and oil are dangerous to other road users becauae they are so slippy. Especially motorbikes. 


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PAS fluid, brake fluid, gear oil and coolant also make rainbows...  I've lost most of them at one point or another... :laugh:

As above though it only takes a small drop to spread, it'll almost certainly be your oil leak in this case.

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Had this in our works car park a few weeks ago, I mentioned it to the foreman who'd just bought another car, turned out it was oil from My car and not only that it was from the gearbox (split 8mm Dia pipe somewhere around the gearbox?) the garage cut the split bit of pipe off, reconnected it then had to fill the oil back up so get it seen to or it might get expensive!

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  • 2 weeks later...

yep the famous injector seals it's a good time to get the rocker head cover gasket replaced when doing the injector seals

my car has a little chuff chuff on long journeys but no leaks i am a biker and i understand any leaks and it's a no go.

just wondering what kind of price for a injector seal replacement

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Depending on the angle of observation and the angle of illumination, reflections from two or more semi-transparent surfaces (the oil on top of the water) can interfere or phase-shift and certain frequencies (colours) can be amplified or attenuated giving the repeating colour pattern :smile:

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