Radiator over flow

Hi Steve
What type of vehicle is it, as some are more prone to head gasket problems than others.
Had this problem with my old 2.6L Pajero, had all the usual tests
you have had done. Replaced all the hoses etc.But they didn't show any thing.
Ended up being the head gasket.It was only a very small leak,
just enough to cause the problem you describe.

Rob.

make sure you have a recovery cap on the radiator
not just a standard cap
mechpete

Steve
also check the overflow hose itself ,once had one that had a split on the inside layer the acted like a one way valve
Vic

hi Steve
i think you will find that a new radiator cap will fix the problem, also it would not cost a lot to have the system pressure tested

kevin

Steve, For the water to be sucked back into the radiator all the connections from the overflow tank to the radiator must be airtight.
Check all the hose clamps are tight, don't just look, try using a screwdriver or spanner as necessary even a quarter turn on a clamp can make a big diifference.
Check that the overflow hose has not cracked or perished, if in doubt replace it.
Make sure that the cap on the overflow tank is airtight too, as only any little air leak may destroy the whole setup.

Disco.

a pressure test is unlikely to find anything - ive had cracked heads -leaking water pumps etc over the years and no amount of pressure testing could detect them.

Is it actually using water from the radiator? A healthy system puts FA into the overflow. listen to bubbling from the overflow pipe into to overflow when warm. If it is using water it would almost certainly be a cracked head as it was fairly common on the 2h/12ht motors.

also check for any external coolant leaks

Ive come across this problem several times before.
But for clarification.
it fills the overflow bottle, then next time you run it, it fills it again, and finally the overflow bottle overflows itself??
and the rad level drops accordingly???


first thing to check is the rad cap, that it actually allows for vac to suck back into the rad, and that it seals under vac so that it dosent suck air from the top seal, and thus the bottom seal / valve dosent bring in from the overflow.

Then check the plumbing from the overflow tank to the rad cap area.
These areas can cope under positive pressure, but pull a vac on them, and they can leak and not draw from the overflow.

One good one I had was a pulsar with the metal pipe behind the block under the inlet manifold that had an o ring to seal said pipe into the back of the water pump.

Fine under pressure, no leaks, but under vac, the o ring was perished, and the cracks would allow air into the system.

It would heat up, push water into the overflow, but not bring it back.
Next heat cycle, it would push water into overflow, but not bring it back.
Finally it would empty itself to the point of overheating.

So check your cap, and hose tightness in general, vac leaks can be strange ones to find.

Trains

Have a similar issue start recently with a GQ patrol, check the coolant when engine cold and it would be an inch below where the cap seals. Overflow never seemed to change in level. Replaced the radiator cap and checked overflow hose for air leaks etc. Could find no sign of coolant leaks including inside the cabin from the heater core. Could go away on a trip and have no problems but when engine cold, coolant would be an inch below where it should be. Could add some coolant and leave the cap off and it would slowly fall back to an inch below. As the height of the coolant would always stay higher than the head I figured it wasn't a cracked head or blown gasket problem. Ended up by passing the heater core as I wondered if it was blocked and maybe creating a air block. On by passing the heater the coolant level in the radiator stayed full. Flushed the heater core and re-connected, whilst it still isn't staying 100% full (about 6mm below) it hasn't to fallen to an inch below full so far. So figure the heater core is the problem!

Did half of this years rally with the cap turned back a notch to get the car home it was spitting coolant everywhere out of the over flow.. It turned out to be a shagged radiator. We thought the worst though as at the same time the turbo hoses blew off. We had a couple of seperate issues that put together looks worse than it realy is.

A few others have said it ..try a new radiator cap.
Had a similar issuue with my Disco ..coolant in the overflow, but tank level would slowly drop. Turned the seal over in the cap and Bingo!

I met a guy in Victoria who leaves his modified Rangie out here and flies down every year from England for his holidays (and we thought Poms didn't hae any tatse) Anyway, he had a similar problem.
A real DIYer, he replacd all hoses ..nope!Took out the radiator, sweated off the top tank off, cleaned it out and re-sealed it. Problem continued. Replaced water pump ..Nup! Finally figured it must be a head gasket issue ..pulled into a freebie and did a head job on his perfectly OK V8. Bugga! In depseration he dropped into a radiator shop, bloke listened to his saga, handed handed him a new radiator cap and said .."On the house mate!"
Problem solved.

Hi Stephen also make sure the tube that is connected to the lid of the overflow bottle make sure the tube is connected up to the right one.. My wifes old car would blow water into overflow bottle but wouldnt suck it back into the radiator. Took me a while to work out what the hell was going on but turned out for some unknown reason why the hell the mechanic even touched it I have no idea but anyway the rubber hose coming from the radiator across the cap on the over flow bottle wasnt connected to the long tube which sits towards the bottom of the overflow bottle therefore could blow in but not suck back out. It was connected to the pressure side outlet of the bottle incase your overflow bottle need to get rid of some pressure due to overfilling etc. Proabaly not your problem but some thing esle for you to check. WHG