Nissan Patrol 4x4 (Africa)

Hi All

I replaced my radiator after the previous one had a leak in the top plastic tank.

The new radiator is in and the system is filled up with water and Nissan Coolant. I did a 350km trip without any heating issues. However..... There is a constant dripping leak at the hose attached to the overflow point by the filler and after driving also resulting overflow spray from the overflow bottle. I went to the radiator shop for some advise and the tested the radiator cap and head gasket for me. Gasket test was fine but the radiator cap was not maintaining pressure so they suggested I start with that. I also did general service on the car during all of this so the oil was dropped. There was also no evidence of oil and water mixing.

To be sure I bought a cap from Nissan which I installed last night. I got the car up to temperature and low and behold it is still leaking water where the hose connects to the overflow at the filler :( I am assuming this is that there is too much pressure building in the system and then water is bypassing via the overflow? Does this not mean the water in the Overflow tank should also be warm? The water in the radiator is warm and the inlet pipe from the thermostat is warm. However the water in the overflow bottle is cool. I have not compared water temps after prolonged driving. Only last night getting the car up to temp. Maybe that water will just take long to warm up?

Could a faulty thermostat possibly be the cause to the problem? Any other suggestions?

Thanks in advance.

Jacques

The water in the overflow tank will take a looooooooong time to get warm as the amount of water that will flow in there will be maybe a cup when going from completely cold to max temp where the radiator cap now allows the water to flow past into the overflow tank.

I have a feeling that there is a pin hole where the small pipe is soldered to the radiator filler. when they check the radiator for pressure holding, I think they plug it lower into the filler hole as they cannot pressurize the radiator from the top of the filler ( if that makes sense )

After a long run and then once the engine has cooled down to ambient temp, was the water level low? It could possibly then be sucking in air into through the same hole instead of from the overflow tank

Make sure that the overflow pipe is not blocked by removing it from the radiator side and then simply blowing on it.

I can confirm the overflow pipe is clear. I can easily blow bubbles into the overflow tank. The leak seems like water is coming out between the thin plastic overflow extension from the filler and the hose if that makes sense. I am not seeing any evidence of water coming from where that little pipe is moulded\welded onto the filler. It is weird as the leak is in the opposite direction of the natural direction of the water flow, possibly indicating pressure towards the filler? Not even sure if that is possible?

Hmmmmm.... very weird indeed

Does your overflow pipe have the little clamp on it? or Maybe the overflow pipe has a small crack in it?

Is it possible that the overflow bottle is too full? I cant see any high\low markings on the bottle. The bottle is filled up with about 50mm gap to the cap.

No, but the max water level is actually very low in the bottle approx. 20cm from the cap top

That is when the engine is cold.

The overflow pipe had the little spring loaded default clamp on it and first thing I thought was maybe it was just not applying enough pressure. I took it off and tried a normal threaded hose clamp bit it is still leaking. I will reduce the overflow tank level (while cold) get the car up temp and do some closer inspection on the leak to try and determine if it is really pushing through between the hose and the overflow nipple filler side. Maybe it is just a collection point for the drops making it look like the source of the leak and there is maybe a small hole at the nipple side.

So from all the feedback thus far I am assuming the thermostat is not likely a contributing factor?