Radiator overflow when still cold

[Suntzuzuki]

I'm having a hell of a time figuring out why my radiator is puking water while it's still cold. Once the thermostat has opened up it's fine but there is a space about 5-10 minutes after it's warmed up where it starts coming back out of the radiator overflow hose.

 

The water is cold so I'm guessing the thermostat hasn't opened yet.

 

Any ideas what's creating all this back pressure to make the radiator start to back up?

[smoke]

Probably a bad head gasket.

[dr.feltersnatch]

agreed with smoke. sounds like a head gasket leaking cyl pressure into the cooling system. go  and buy a block tester 

http://www.autozone.com/autozone/accessories/Tools-Garage-and-Equipment/Block-Tester/_/N-25dh

[smoke]

Or if you plan on going a little south anytime soon, swing into my shop and I can do a leakdown test for you.

[wayno]

Did you change the thermostat recently?

What engine do you have?

[Suntzuzuki]

I was afraid of that (or have been in denial). I'll get the block tester. I replaced the thermostat as soon as this started happening.

[datzenmike]

This is an easy fix.

Drain rad at least half way.

Remove air filter and cover top of carb.

Disconnect exhaust down pipe, fuel line at pump, fuel pump, top rad hose, carb electric choke wire, throttle cable, plug wires, intake and by pass hoses, top heater hose from head.

Remove valve cover.

 

Block cam from turning and loosen cam sprocket bolt, don't remove yet

Set motor to TDC compression on #1, set hand brake and place in neutral.

Use a wooden wedge to jam down between timing chain and the two guides to prevent the chain tensioner popping out. If you don't know what this means find out first, it will save you about 4 hours of unnecessary work if you don't.

Mark the chain and cam sprocket relationship for proper assembly

Remove the loosened cam sprocket bolt, fuel pump eccentric, and the cam sprocket. Let chain fall down between guides.

 

Remove the two 10mm bolts at front bottom edge of the head and the timing cover.

Now loosen and remove the 10 head bolts.

Lift head and both manifolds off block, try to keep level as possible, tilting up just enough to wire wheel the head surface clean.

Put rags in the middle two cylinders and clean the block surface. Cleaning piston tops is not necessary.

Clean out the bolt holes.

Check head surface for warpage. If warped, the manifolds must come off but much easier with the head off the block. Have a minimal amount machined off... about $30-$50.

Head and block surfaces must be spotlessly clean.

Instal gasket dry, never with any dressing or sealer.

Be sure the two aligning dowels are still in block.

Put head on.

Clean and reuse old head bolts if undamaged. Wipe threads with oily rag. Pup drop of oil under head bolt and on top of washer.

Tighten middle two bolts, then the two in front of them, then the two behind, then the front two and then the back two. Tighten to 20 ft lbs. Do again in the same order to 40 and then again to 60 ft lbs. Don't forget the two 10mm at the front

Instal cam sprocket and line up your marks, don't forget the fuel pump eccentric.

Remove the wedge.

Finish replacing and connecting the rest. 

[Suntzuzuki]

If I'm going to go through the trouble of taking the head off, shouldn't I just take it to a machine shop and have it totally gone through? 

 

Any places in Washington you trust to do this?

[smoke]

If you have the extra bread to do that and if it has a bunch of miles on it, yes, that would be the best move. But if it's a fairly new engine, it would be a waste in my opinion.

[ggzilla]

The factory service manual does not recommend refacing the head as part of a rebuild or gasket change. It does outline checking for flatness.

 

Its a bad move if the head is not warped. And most bad gaskets are not due to warping - though some are, so check!

 

Use a 2-ft or longer level, and if you can fit a 4 thousands feeler under it then have the head skimmed and remember to compensate when assembling.