After jumping to conclusions in my last thread, I took the radiator cap off the other day to check if any coolant was missing. While doing this I though to myself that given how much they cost, perhaps it would be a good idea to replace it with a new one.

 

I've spent a bit of time on Google etc. and I'm under the impression that the standard cap pressure is 1.2 bar - however the one fitted to mine is only 0.9 - judging by the numbers stamped on it...

 

Are any of the resident Zed gurus able to confirm what the correct pressure for the radiator cap is? I would like to double check before I buy one and find out that they vary by model/year or there is some other factor that I'm overlooking.

 

My car is a 92 TT Auto (now manual)

 

Thanks all!

This is a good question, every time I’ve replaced my rad cap (about 4 times over the years), the OEM cap has been rated at 1.2bar as shown on the cap. I always assumed this was correct as it’s the Nissan part number listed for the car. It’s funny you mention that your previous cap was rated at 0.9bar as the FSM seems to suggest that for the test criteria:

 

 

[emoji848]

The '95 FSM has this:

 

The Nissan OEM cap is indeed rated at 1.2 bar. Lots of aftermarket caps are less; ranging from 0.9 to 1.1 - personally I'd stick with an OEM one! Too low a rating, and the cap will allow coolant to pass into the overflow tank at a lower pressure - so essentially no more effective than an old worn-out one.... And too high a rating could cause pressure to build in your cooling system, placing additional stress on old components!

IMO, for the cost, I'd have them as a serviceable part. Generally it's the spring for the overflow that can gets gummed up over time, however that's mostly due to coolant being left in for too long, they stick closed giving a potential over-pressure situation. As above, get an OEM one, they're really cheap and have the correct pressure rating/spring pressure.

Thanks for the replies guys. It didn't occur to me to check the FSM.

 

IMO, for the cost, I'd have them as a serviceable part. Generally it's the spring for the overflow that can gets gummed up over time, however that's mostly due to coolant being left in for too long, they stick closed giving a potential over-pressure situation. As above, get an OEM one, they're really cheap and have the correct pressure rating/spring pressure.

 

I agree Simon, I have always considered them serviceable and would only replace it with an OEM part.

 

I'm aware that you can get aftermarket caps with higher pressures, but I'm not 100% clear on why you would opt for a lower pressure, unless you were concerned about ageing hoses etc. - but then you'd just replace the old worn components.

 

Anyway, I'll be ordering a new 1.2 bar cap shortly.

 

Thanks all.

I don’t think you would have an issue with a 1.2bar cap but your finding is interesting that earlier cars cane with 0.9bar caps though. I can only assume that some climates reported overheating problems and so the OEM decided that the system was capable of the increased pressure to raise the boiling point accordingly.

Should i put the 1.2 cap on my 1990 na? It has the 0.9