Coolant spurting from radiator after rebuild

[soldave]

Have finally got the engine running and running semi-right in my Evo III, but I've got one thing that keeps running through my head and it's about the coolant.

I made sure the system has no leaks in it now and it seems to be airtight. Filled the radiator and started the car (keeping radiator cap off) & got it to operating temperature (heater on full blast of course to help burp the system). Now I had the bleed bolt near the thermostat housing out and was ready to put it back on when it started coming out of there. But it never did really. There was steam after a while but that was it. And also after I revved it up a little the coolant started to spurt out of the radiator; and not like overflow but spurt out. Temperature gauge was giving me normal temps though.

Am I right in thinking that's not normal? If so then I can think of just 2 things that could be causing it:
1. Thermostat isn't opening at all or isn't opening fully. Possible but I think the upper radiator hose was warm/hot
2. There is a blockage somewhere in the coolant system, causing a hotspot and so causing the coolant to bubble up and spurt out.

If it's the 2nd one, I'm wondering if a good flush (flush radiator, remove lower radiator hose, start car and pump in cold water into the top of the radiator until I get clean water coming out) will help.

Just a little worried that it shouldn't be doing that.

 

[rlacasse1]

The only reason I know for coolant to really "spurt" out is because the headgasket isn't sealed.

Let the car sit and cool back off, then without starting it just crank it over with the radiator cap off of it. If you have coolant jumping out then your headgasket isn't sealing and it's letting compression find its way from the cylinder to the coolant system.

Did you deck the block and head before you rebuilt it? And what head gasket did you use?

 

[soldave]

No decking facilities here on island so I didn't do that. Both block and head were well cleaned up though with virtually no imperfections. Stock composite headgasket was used.

Compression test before initial startup was giving me around 160 for all 4 cylinders, and that was obviously before the piston rings have had time to seal properly. So I would think the headgasket is ok, but I could be wrong.

 

[rlacasse1]

I would at least try it.

Only other thing I can think of is when your thermostat opens and closes. The level seems to drop when it opens and it rises a little when closed. So it's possible that could be happening. But I don't think it would be that bad, unless it's because of the heat. I've never taken a cap off a hot radiaotor.

 

[soldave]

Will give it a try. Can the engine be stone cold when I'm testing it this way with the starter, or does it need to be warmed up initially first?

As the engine started and warmed up the coolant level was staying at the top of the radiator pretty much, just needing a little top up as it burped.

Should say I had enough time for the car to heat up fully, attach timing light, set timing and do other stuff before it started spurting out

 

[rlacasse1]

I just don't know how it acts when it's hot.

I would do it cold. Just take off the cap and see if she squirts.

 

[soldave]

I will, but what I'm saying is when the engine starts up and is running up to operating temperature there are no bubbles and no spurting at all.

 

[rlacasse1]

I thought you said it is squirting when it is hot?

I'm confused now.

Look, if you crank it and it squirts you have a headgasket issue, which isn't out of the question since neither the block or head were milled.

 

[soldave]

I thought you said it is squirting when it is hot?

I'm confused now.

Look, if you crank it and it squirts you have a headgasket issue, which isn't out of the question since neither the block or head were milled.

Affirmative. What I'm saying is that with the engine cold (which is as you stated I should do) and the radiator cap off there is already no spurting. It only spurts when it gets hot, and usually after some revving).

 

[rlacasse1]

Then I would think it's fine.

I mean at that point the thermostat is opening and closing and doing it's thing and it would make sense that it would jump a little if you revved it cause the water pump would start moving more fluid.

I wouldn't be to concerned with it.

Just watch your temp gauge just in case.