help oerheating

[ryry]

me and my dad have a maxum 4.3 v6 2400scr .. for some reason it over heats and does it pretty quick . when it overheats it blows the cap off the reservoir .we have to stop and wait it out befor we can go again ? wehave checked everything we know how to .. plz help

[ss3964spd]

My first guess is that the raw water pump impellor is bad. Any idea when it was last changed?

[mmwjr]

"Blows cap off the reservoir", so you have a freshwater closed system? On the open side (raw water) when was the impeller last changes? Could be clogges exhaust manifolds and elbows, how old are they? On the freshwater side t-stat, engine circulating pump.

What out drive do you have? Alpha? Bravo 1, 2, or 3? This will tell us where the raw water pump is located.

I'd get a handheld IR thermal gun and take temps around the engine t-stat housing, manifolds, ... anything over 160 F is too hot. this can help you pinpoint the location and problem.

[Nehalennia]

Yes we need more info to help you properly. What have you done besides "everything"? What does that entail?
How long has it been since your exhaust manifolds, risers and elbows have been replaced?
How long has it been since your impeller has been replaced?

[ryry]

yes my dad did the impeller and its a alpha 1 .. we just tore it all the way down thinking it might have been a head , intake , exhaust , gasket ... we are waiting for them to came in tomo .. and put back together . hoping it works .....what else coiuld it be

[mmwjr]

t-stat!

circulating pump!

How did the manifolds and elbow water jackets look when you removed them? You didn't answer my question if it is a closed cooling system.
Sounds like you jumped in before diagnosing the fault.
Do you have a picture of the engine before you took it apart that you can post?

[ryry]

they looked fine .. no its not a closed cooling system it the 4.3LX v6 vortec 4bbl ..and dont have a pic of the engine sorry ...dad was so sur it was a head gasket that we just jumped in to it lol i thought from the begining that it was something to do with the cooling system .. and now that we got this far its looking like i was right
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[mmwjr]

So what were you refer to by saying "Blows cap off the reservoir"?

Hard to give further advise on troubleshooting with it taken apart. Did you dad run a compression test if he thought the head gasket was blown? Both heads? Was the engine running bad and overheating or just overheating?

You are probably at the point where you need to reassembly and go from there.