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Radiator Overflow Always Empty.

Bl4cK32

By Bl4cK32,
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Bl4cK32 Grand Master

Bl4cK32

Posted
Posted

i had my motor rebuilt a while ago, and the coolant system is fine but im doing a flush soon.

I noticed that when i always top the overflow to the max line, when i go for a drive it will always overflow the bottle, then suck back what it needs into the radiator leaving it empty.

I have no leaks in the system, and the cooling is perfect in the car, its just the overflow never likes to be full, just empty. The car has a new clutch fan, a new water pump was put in when the motor was built too. Basically the coolant system is 100%, except it doesnt like any water in the overflow.

Where does other people's levels sit in the overflow, and would there be anything wrong with the coolant system?

thanks.

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Bl4cK32 Grand Master

Bl4cK32

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its a speco(?) one with with the button jobbie on top. I'll try replacing it, but it doesnt seem to be the problem as it opens and closes....

I dont like the higher pressure caps, as id rather the overflow let go, than blow a radiator hose when im out somewhere....

Edited by Bl4cK32
predator Grand Master

predator

Posted
Posted

mine always "disappeared" just like yours..

just before i pulled the rb20 out, it started overheating chronically. I believe the thermostat was on its way out, as I tried the usual suspects but it still kept doing it.

I don't think it was the radiator cap... but probably time to replace that as well.

SteveL Mentor

SteveL

Posted
Posted
what does the button in the middle of the radiator cap do anyways ?

Usually a button like that is to allow safe release of cooling system pressure, esp when hot.

In terms of the loss of coolant, there has to be a leak somewhere for that to occur and the overflow tank is doing it's job of replacing the loss from the main system. It's a case of checking all hose joints, welch plugs, etc for weeping/leaks. I had an R31 that had a similar problem which frustated the hell out of me for over year......I only found the leak (read: slow drip) at a hose joint with the car up on the hoist and the system pressurised, but it took a lot of finding.

Bl4cK32 Grand Master

Bl4cK32

Posted
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Motor has been rebuilt, and all parts are new (besides rad cap) thermostat is genuine nissan rb20 item, new pump, new clutch fan.

It doenst have appear to leak as the level in the radiator stays the same all the time (once overflow is empty).

I'll go over the lot thought to check it. thanks guys :P

PlasticStan Enthusiast

PlasticStan

Posted
Posted
It doenst have appear to leak as the level in the radiator stays the same all the time (once overflow is empty).

Funny, mine does exactly the same. I first noticed this over a year ago. Checking the radiator today, the water level is still right at the top, but the expansion tank is still empty. ????

Will be doing coolant flush and change when installing my new turbo, so I'll replace the rad cap aswell.

siksII Grand Master

siksII

Posted
Posted
Motor has been rebuilt, and all parts are new (besides rad cap) thermostat is genuine nissan rb20 item, new pump, new clutch fan.

It doenst have appear to leak as the level in the radiator stays the same all the time (once overflow is empty).

I'll go over the lot thought to check it. thanks guys :laugh:

That doesnt make any sense, it has to leak otherwise where would all the water from the overflow bottle go?

I had this problem on my old skyline and it turned out to be the headgasket slowly leaking coolant when the system was at very high pressure.

Take the car to a radiator shop and get them to pressure test it, they shouldnt charge you much and i reckon they will find a leak :D

Bl4cK32 Grand Master

Bl4cK32

Posted
  • Author
Posted (edited)

When i refill the overflow, then go for a long drive, i can hear it bubble out the overflow - ie blow out the water i refilled it with, then as it cools it sucks back in all the contents of the overflow leaving it empty again.

did that make sense?

It shouldnt be the headgasket, as the motor was rebuilt with a 3 layer cometic metal head gasket, which has inbuilt o-rings :laugh:

good tip though, i'll get it pressure tested then i'll know for sure :D

Edited by Bl4cK32
SteveL Mentor

SteveL

Posted
Posted
When i refill the overflow, then go for a long drive, i can hear it bubble out the overflow - ie blow out the water i refilled it with....

Most definately not normal. Either your radiator cap is not holding pressure (ie releasing pressure too early), or you have a cylinder (or cylinders) leaking compression pressure into the cooling system causing the cooling system pressure to exceed the rad cap rating. IOW a blown head gasket. The fact that you say the coolant is 'blown out' and there is bubbling suggests this is likely. Have your cooling system pressure tested (free at most radiator repairers).

Bl4cK32 Grand Master

Bl4cK32

Posted
  • Author
Posted

it only has the bubbling sound, and overflows when the overflow bottle is full. If it was the head gasket, it would blow out a lot more, and be hissing etc all the time from long drives.

It just hisses when the overflow is full. Only then it blows it out, and sucks it all back it. Every other day its fine, and woter temp sits at 84deg via the pfc hc.

Id definitly say its me radiator cap shitting it...but i cant be sure till i replace it. Will do tomorrow :P

Im gunna get a pressure test done too, to find leaks :D

  • 3 weeks later...
Interloper Veteran

Interloper

Posted
Posted
I noticed that when i always top the overflow to the max line, when i go for a drive it will always overflow the bottle, then suck back what it needs into the radiator leaving it empty.

Where does other people's levels sit in the overflow, and would there be anything wrong with the coolant system?

thanks.

i get the same problem, if i fill the overflow bottle it will leak out when i stop. last time i did that it leaked out a puddle on my garage floor after a drive. But the radiator is always full and the car never overheats stays around 80 - 85 degrees.

a bit of a puzzle, but i've got use to having a almost empty overflow bottle now so i just ignore it :bunny:

Dizmo Enthusiast

Dizmo

Posted
Posted

Check the level of oil when the car is warm at idling then fill the bottle and check the level when bottle is been emptied. If the oil level changes u either have a crack in the gasket or a warped head.

Has the temp level changed whilst goin for a drive.?

Let the car idle for a while on ur driveway or a clean surface. c if any coolant is leaking anywhere. Tighten all clamps and check the bottom and top tanks of the radiator to see if there are any leaks, also check the cap and hear if there is any hissing or coolant loss.

Other than that take it to a radiator place for a test.

Ryan

Bl4cK32 Grand Master

Bl4cK32

Posted
  • Author
Posted

It isnt a head gasket as im running a 3 layer metal one, and the head has been fully rebuilt less than 15k kms ago.

Water temp is always 80-85 deg. Only goes up to 90 on a hot day. No leaks anywhere in system.

Only thing left is the cap...which i havent found a replacement yet, as repco tried to sell me something that was different to the one on my car, even after i pointed out it was different....damn ignorant sales jerks think they know everything

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