Dear all,
It has come to my attention that people are experiencing an issue with their radiator caps not allowing the cooling system to suck the coolant back to the reservoir as the car cools. This causes the top hose on the radiator to flatten after use of the car.
In most cases, simply buying a radiator cap of mx5parts or another reputable dealer will help. They are only around £5 for an after market one and perfectly fine to use. However!, you can save some money and free up the valve that is stuck. This will eleviate the issue, at least until you take delivery of your shiny new one!
You will notice two major seals on the cap. A larger rubber seal, nearer to the cap and a smaller rubber seal nearer to the internals of the radiator.
- Clean the cap off in some fresh water and get rid of the oxidization.
- Push the smaller rubber part in and out to free it up.
- You will notice, on the end of the cap is a metal washer keeping the smaller rubber seal on. Carefully, run a flat bladed screw driver around and inbetween the washer and the rubber seal to get rid of the crud. The seal becomes adhered to the washer which is part of the issue.
- With the flat bladed screw driver in between the washer and the rubber seal, wiggle it a little as you move i around to make a small and even gap to free it up.
Don't go to far with this, but this should help.
Ofcourse, some of the issue can be due to hardness in the return pipes to the reservoir so give them a good squeez and a roll up and down to break up the rubbish in them as a precaution.
Radiator caps are pretty simple things but they do tend sit on the car from it's birth and since they have been exposed to water for that period it's no wonder the parts stop moving around. It only takes a few minute to do this but is quite pleasing when it works, even if you are only saving £5 or so.
A quick edit in response to Peters post below, obviously if you have a build up of hardness within your cooling system, it won’t be operating as efficiently as it should be and over time that can lead to failure of other components. Also the gunk can shift into the water libraries within the head and block which may lead to uneaven cooling in those areas as well as in some extreme cases actual blockage. With this in mind you should consider flushing your system and renewing old hoses. Many of our MX5s are aging now so some hardness is to be expected. Small amounts is unlikely to cause major issues and actually quite normal. The smaller hoses are the weaker points of the system for blockage as well as the radiator itself. I have experienced a radiator that was perhaps 60% blocked. This is digressing a little from the actual post topic however.
Let me know if this post has helped you out!
