Issues With Overflow And Radiator.

[Gameboy]

OK, from my understanding, the radiator cap is meant to seal the radiator and when there is to much pressure, it pushes the radiator cap spring and releases some pressure and then it seals again. Correct?

Problem I am having is that the coolant is getting dumped into the overflow before pressure builds up. It dumps the entire contents of the rad into the overflow and then pisses out. When the engine cools down, it sucks it back in but leaving it dry as most of it has pissed out on the road.

The car doesn't over heat when this happens Just the smell of coolant and a kettle sound. The temp stays on half.

Ive done a gas test and it shows no problems there. I bought a genuine Nissan rad cap and it still does it. I took the radiator to a specialist and he reckons that the radiator cap is 2mm to short and isn't even making a seal and insists that the cap is the wrong one.

This doesnt sound right so I thought id ask what you guys think. Im thinking of getting a big washer and gluing it into the radiator neck so the bottom of the cap makes contact.

Advice??

[Ben C34]

Radiator expert sounds right.

You should be able to feel the cap seal onto the rad when you first put it on, then when you do it up it compresses the spring inside it to allow the outer edge to seal.

[89CAL]

Yeah the cap and the sealing surface are the only thing that controls flow between the radiator and overflow bottle. Nothing else will cause coolant to pass between the two.

Post up some photos of both the radiator sealing surface and the cap so we can help a bit more

[GeeDog]

You can check if the cap is sealing when cold by sqeezing the top radiator hose. Make sure the radiator is full of coolant first - if the cap isn't sealing, when you squeeze the hose you will see coolant going into the overflow bottle - this shouldn't happen until the pressure builds to the cap's rating, which it won't reach by sqeezing the hose.

[Gameboy]

Great, thanks for the replies and yeah when I squeeze the hoses there is coolant going back and fourth.

[89CAL]

Does it feel tight when you do the cap up? As in do you have to press it down to get it to go in.

For some reason something doesn't look right but I'm not around my car to have a look to compare. Was the cap definetly for a skyline?

[Gameboy]

Does it feel tight when you do the cap up? As in do you have to press it down to get it to go in.

For some reason something doesn't look right but I'm not around my car to have a look to compare. Was the cap definetly for a skyline?

Nah dont have to press down at all. Just put on and twist. The cap is definitely for the car as I asked for it at the Nissan dealership.

[GTSBoy]

BHG?

[Gameboy]

BHG?

I tested for exhaust gases and it was fine. The car also runs perfect engine doesn't miss a beat.

[GeeDog]

Great, thanks for the replies and yeah when I squeeze the hoses there is coolant going back and fourth.

Looks like the cap isn't sealing than. Have you got a way to measure both the cap height & the radiator neck internal height - the cap should be a bit bigger. A vernier caliper would be the go.

[scotty nm35]

I have seen this many times lately, if you can't feel the force of the spring as you push it down, the cap is too short. Get a new one that sits a little further into the radiator.

[Ben C34]

I have seen this many times lately, if you can't feel the force of the spring as you push it down, the cap is too short. Get a new one that sits a little further into the radiator.

Radiator specialist said it.

I said it.

89CAL said it.

Scotty said it.

It is pretty obvious. Get a new cap.

[Gameboy]

Radiator specialist said it.

I said it.

89CAL said it.

Scotty said it.

It is pretty obvious. Get a new cap.

Its a brand new cap from Nissan. Ive even checked in car shops for other caps and they are all the same size. Its so weird...have even compared with a mates Skyline cap and it looks the same. Ill see if I can just buy a longer one or use a washer or something.

[ck_chino]

though it may be a new cap from nissan. whos to say that it isnt defective from factory? a worn rad neck seat where the cap seal interfaces with rad could be worn out - which would mean a new rad but for what its worth try a new cap before the rad itself.

[89CAL]

Well more to the point, whos to say they didn't go and grab the first radiator cap they could find OR for some reason your radiator is different.

I'm not saying I'm right but these things do happen

Go to supercheap and have a look at the ones they stock, compare and buy one that seems better. Caps are different, they should have one that will work. And make sure its a 1.1bar cap because .88 seems low for some reason. I cant remember what my stock cap was but think it was about 1 bar.

[niZmO_Man]

Its a brand new cap from Nissan. Ive even checked in car shops for other caps and they are all the same size. Its so weird...have even compared with a mates Skyline cap and it looks the same. Ill see if I can just buy a longer one or use a washer or something.

Swap cap with your mate for a day. 88kPa seems a bit low.

[Gameboy]

I couldnt find another cap so I found a rubber grommet that fits perfectly and sits just below the overflow hose hole.. I glued it in with Sikaflex will see how it goes once its dry. Good point about the guy at Nissan just grabbing any cap.