521 radiator overflow

[fisch]

Sorry if this has been covered, but I did a search but couldn't find anything.

 

Alrighty, if you watched the video of me in the back yard with my 521, you know when I shut down, my radiator overflowed out the overflow tube.:eek:

 

Can I just get an overflow container? To my understanding of the manuals, the 521 did not have an overflow container. It just has a hose that runs down the side of the radiator to no where.

 

I also schooled myself on what is happening. Pressure builds in the radiator which compresses the spring in the cap, thus exposing the overflow tube exit.

 

So could it also just be a weak cap spring? Looks fine, but it is a generic cap that came with it. However it is rated for the right amount of pressure.

 

So what is the proper course of action?

 

A) Find a location to install a later model overflow container and bracket?

 

B) Get a new cap, preferably a NOS one? ($25 - $30 on the bay)

 

C) Could everything be working fine, which means there is something else causing the overflowing?

 

Remember I am an idiot when it comes to these things. Here is the crime scene photo!

 

[datsunaholic]

A blown head gasket can cause that. Blows combustion gasses into the coolant, whhich overpressurizes the system. I've had a few do that- I was doing a valve stem seal change using compressed air to hold the valves shut, and had air blowing out my radiator vent. Popped the cap- was gurgling pretty good.

 

Funny, though, the engine runs fine. But it has a definate problem.

[flyerdan]

If you fill the radiator to the very top, heat expansion will force some coolant out, that is why all newer rigs have recovery tanks. I believe I have a 1 liter pop bottle zip tied to the bottom side of the radiator on mine. The radiator cap has a spring loaded pressure relief, and a smaller vacuum release inside. When it cools off, the vacuum pulls the coolant back into the radiator for better heat transfer.

[SHADY280]

his engine wasnt running tho, or what i gather from what his video said. you can buy universal overflow tanks on the bay as well. you can buy a new cap as well, just for good insurance, but even with a good cap it may still happen. in the good old days, it didnt matter that it went all over the ground, today its a bad thing, hence the overflow tank. you can even use a 600ml pop bottle with the hose inserted into it. when its running it will suck it in, then when it cools, it blows it out to the bottle. now that its dumped out, itll prolly never do it much again, cause it emptied out the extra!!

[SHADY280]

dang beat me to it!!

[fisch]

A blown head gasket can cause that. Blows combustion gasses into the coolant, whhich overpressurizes the system. I've had a few do that- I was doing a valve stem seal change using compressed air to hold the valves shut, and had air blowing out my radiator vent. Popped the cap- was gurgling pretty good.

 

Funny, though, the engine runs fine. But it has a definite problem.

 

Now your scaring me Holic! I should add that there was no issue with the overflow until I turned off the key and thus the fan stopped running. Could the above still be a cause if it only happen on shutdown?

[fisch]

Damn you guys got in three posts while I was typing that last one! I took off the cap and peek in there and I can see the little core-drain holes so it emptied that far at a minimum. They recomend filling half an inch from the bottom of the neck, so that is where I had it.

[datzenmike]

Whenever you shut down a motor there is residual heat still making it's way through the block to the coolant passages. With the fan now stopped the temp will rise slightly and pressure will increase too. The rad cap allowa a pressure of about 14 lbs which will usually cover most of this, and a small amount may burp into the overflow can.

 

I would say that is too much. The rad cap may be bad and allowing any pressure to push coolant out. They are cheap $12 and under. Rather than guess, just change it.

[fisch]

Alright so I will do A and B! First on the list was this little score. Just snagged it for 5.50 on ebay. Stainless Steel overflow tank. I only found the auction a minute before it ended so I jumped on it with out thinking. But I hope that if a soda pop bottle works, this will too. Whatcha guys think?

 

I think for a over flow to work, the hose has to be submerged for it to return. I am not sure what goes on inside these canisters, but I guess if it is designed to be an overflow, it should work?

 

 

[datzenmike]

In order for the return to work properly a rad cap for that purpose is required. If not, it's a one way only into the overflow can.

[SHADY280]

any rad cap should work for that, shouldnt it? last time i checked they were all the same. that overflow is perfect!!! and for 5.50, you cant beat it. i gotta get me one of those for the 620. and if you increase your rad cap pressure it also increases the boiling point of the fluid inside the cooling system, also helping it cool better. id go to a 16lb. cap.

[fisch]

and if you increase your rad cap pressure it also increases the boiling point of the fluid inside the cooling system, also helping it cool better. id go to a 16lb. cap.

 

I can do that? Cool! I just assumed more pressure that 13lbs might burst something on an old L16!

[djmoreron]

Alright so I will do A and B! First on the list was this little score. Just snagged it for 5.50 on ebay. Stainless Steel overflow tank. I only found the auction a minute before it ended so I jumped on it with out thinking. But I hope that if a soda pop bottle works, this will too. Whatcha guys think?

 

I think for a over flow to work, the hose has to be submerged for it to return. I am not sure what goes on inside these canisters, but I guess if it is designed to be an overflow, it should work?

 

 

 

 

 

oil catch cans would work too. lots of people make "performance" versions of the overflow tanks. they claim its for looks, but i think most of them look ugly anyway... and their upward of $80

 

 

 

...had no idea increasing rad cap pressure increases the boiling point of the fluid. good stuff

[DISLEXICDIME]

i just took my over flow from a 620:confused:

[SHADY280]

well there is always a slim chance that if your cooling system has a really weak point, it will help find it, but if its that weak, youll be glad to fix it. being a wanna be mechanic has its upsides, like crap loads of useless info like that!!

[fisch]

i just took my over flow from a 620:confused:

 

I thought about that for sure. But for $5.50 I thought it'd be cool to have at least one shiny thing in an otherwise ratty looking engine bay!

[datzenmike]

any rad cap should work for that, shouldnt it? last time i checked they were all the same. that overflow is perfect!!! and for 5.50, you cant beat it. i gotta get me one of those for the 620. and if you increase your rad cap pressure it also increases the boiling point of the fluid inside the cooling system, also helping it cool better. id go to a 16lb. cap.

 

You could check, but I'm sure. If your system has no overflow there is just a pressure relief cap on it. If it overpressurizes (for whatever reason) the water pushes past a spring loaded seal. When the pressure drops the cap is tightly sealed by the spring and the coolant can't get back in.

 

On cars equipped with coolant recovery, the cap has an additional one way valve connected to the overflow pipe. Once cooled and contracted the excess coolant is sucked back into the rad. If the system is working properly, and you open the drain in the botton of the rad, the coolant will syphon from the coolant recovery tank back into the rad. This won't work wiht an old style rad cap.

 

I put a coolant recovery in my old 521 and had to change the cap to make it work. If you don't, you will have to manually pore it back into the rad.

[JWilk_SD]

If it has been sitting that long at the least you should replace hoses and Thermostat and flush the system if you havn't already. If the thermostat is stuck that could be causing your overflow.

[hang_510]

oil catch cans would work too.

i need one of these now...for oil :rolleyes:

anyone got one for sale???

 

 

 

i grabbed (from a JY maxima-?yr) an overflow bucket that is part in the battery hold down. the bucket slide mounts on to it. flipped the rod and bolted it through where the stock horn mounts, slipped the bucket back on. looks stock :D