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L18b radiator blew its top!


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I was tooling around in my truck when I noticed quite a bit of smoke coming out the back when downshifting.

smoke screen style on the drivers behind me...sorry, guys.


Then I hear a "POP" under the hood, and fluid was spraying on the windshield from under the hood.

Lots of smoke, I park it on the side of the road.


I thought for sure that it was oil, and my motor was f'ed.



I raised the hood, and found that the radiator had blown the cap off, still screwed into the female end of the radiator.

It was tangled up in the spark plug wires, with coolant all over the damn place.

The break was super clean...there was a bit of an epoxy of some sort on the bottom...looks like it might have been "repaired" before.


The upper radiator hose looked like it was vacuumed shut.


I poured more coolant into the radiator and started the engine.

Coolant was pumping out of the radiator, which means the water pump is working...


Im not sure what else could have caused this.


Any ideas?

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L18b... I missed that.


An L18b would presume that there was an L18a 6 cylinder made. Haven't seen one.


very rare...nissan made a few to power mechanical unicorns for an amusement park.

super rare.

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aaargh. Sorry to hear that.


It sounds like it will be an easy fix, just get a new cap. Or a nother radiator. Probably didn't hurt the engine.



The piece that you screw the cap into broke off with the cap still attached.


guess I'll just give another radiator a shot, if welding that piece back on isnt a good option.


I shut the engine down right away, so hopefully there was no damage.

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You say an L18 rad so I assume it's a stock one and not an aluminum one with crimped on tanks. Rads are soldered. Epoxy is a fix or mod and definitely NOT the way to do it.


yes, this is a stock radiator...guess the soldering from the factory gave out under pressure.


im hoping that there isnt another part somewhere that failed causing the pressure to surge and make it pop.

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Being that they dont make the radiator that fits correctly in a 73/74 620 anymore. Chances are that you are going to need to look into getting yours repaired. So dont just throw the parts away yet.


However, this seems like an odd failure of a radiator. I think that you might have something else going on that is the source of the problem. Like a bad thermostat causing excessive heat or a bad head gasket allowing combustion pressure into the cooling system.


And, absolutely do not re-use that radiator cap. It should have released any excessive system pressure long before the top blew off the tank. For that matter, the cap could be the source of the whole problem.

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In order to get hot enough for the solder to melt it would have to be 3 time the boiling point of water.


The rad cap is a pressure relief model usually set for 14 PSI so compression would be vented.


One thing solder is no good at is mechanical strength so most wire connections are twisted together to make good contact and strength and the solder just assures good conductivity. On rads it only seals and doesn't really (or shouldn't ) hold stuff together. All parts are crimped or snug fitting first before soldering.

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The radiator was probably old and tired and worn. These thing happen all the time, I had my l20 radiator completely crack in half, and my radiator that I used in the KA that's in my 510 now started springing leaks all over.


All I did was go to a pick n pull, pulled out a radiator out of a car with same displacement or more, about the same measurements and walla :)


My car runs now on a radiator I think from a v6 altima but I am not sure, but the KA with a NISMO 160 degree thermo barley reaches 200, in 100 degree weather stuck in a California traffic jam hehe.


I know that the v6 Fiero radiators are loved by l18 and l20 guys :).


Here is a video of my radiator :).





I forgot to add, in my pick an pull I can buy out warranty for 35 days for 8 bucks :).

I do recommend if you have the option, since you still pay less than 50 bucks :).

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There is a 510 with L20B at arlington Pick-N-Pull, radiator looked good. Would that fit?


It's usually cheaper to switch radiators than to get one repaired. Pick-N-Pull radiators are only $29.99 with trade in.


Yes! Did you happen to pick it up? If so, I'll buy it from you

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