Water not returning from overflow.

[Redbo]

Hello

I have a 89 patrol with a 350 chev on straight gas. The previous owner fitted a low coolant alarm to the radiator which always seems to go off. I have had been to natrad and they pressure tested the cooling system and found no faults.

I believe its a standard gq radiator

I have never found a leak but all i can find is that the overflow bottle seems to fill up but not return the coolant to the radiator.
I have bought a new radiator cap and it doesnt seem to make a difference.

any ideas?

[5inchgq]

Are the hoses to the overflow bottle on the correct barbs on the bottles lid ?

[brissle]

the only time i had a similar problem was a stuffed head gasket presurising the cooling system and blowing coolant into the over flow bottle

[Redbo]

Just checked then.

Unscrewed the overflow lid pulled off the little angled hose its clear.

Blew down the tube that the hose connects to and can say that its going to the neck of the radiator just below the cap.

Not sure if its meant to be sealed or not but i can blow down the tube and there seems to be air coming out around the cap.

[5inchgq]

the only time i had a similar problem was a stuffed head gasket presurising the cooling system and blowing coolant into the over flow bottle

My last TD42 did that just after I fitted a turbo was going to be my next suggestion. A compression test will diagnose this.

[Redbo]

So a head gasket wont show up when pressure testing the radiator with the engine off?

The tested the radiator and it held pressure with the engine not running.

[brissle]

didnt show up with mine either but it was stuffed

[Clanky]

I just had this problem on my TD42 (unfortunately mine was the head gasket)

1) try a new radiator cap. Sometimes they stick or can play up ( especaily the return valve ) I had one that wouldnt let the coolant return to the rad when cool and it actually sucked the top radiator hose flat. To look at it it was ok.
2) Check the hose barbs and hose on the radiator neck to the bottle. I have a PWR radiator and the little alloy barb on the radiator neck had a tiny pinhole in it. This was allowing air to be sucked into the radiator when it cooled down. Was a bugger to find but look for any coolant crusty areas.
3) Othere than that you need to look at the engine components ( waterpump, head gaskets, thermo housing etc for leaks.)

[Jake GQ..]

i had the same problem with my tb42 it was a stuffed head gascket which in turn cracked the head. i did a presure test and had a couple of machanics look at it. my money is on head. sorry

[BadMav]

Check you have the hose on the right tail at the bottle.

[garth]

Gudday

alot of the time a leaking head gasket - or in fact a cracked head will only show once the engine is hot, so start there.
Take the thing for a good run then check the over flow tank, if you have any bubbles you've got a head or head gasket issue.
They usually let go on cylinder 5 and 6 into the water jacket.
When you do the install use all new gear,a genuine head gasket and copper coat spray....probably a good time depending on K's to look at the precom chambers while its off.
unfortunately when running 30PSI boost you go through this diagnostic pretty early in the build process.

regards Garth

[bilby]

So a head gasket wont show up when pressure testing the radiator with the engine off?

The tested the radiator and it held pressure with the engine not running.

Probably wont as the thermostat is shut unless the water is running temp hot .

Get a exhaust gas test done on the radiator and then you can eliminate the blown / cracked head gasket .