overheated 302 runs rough

[SPOONMAN1]

A good friend ran his 96 302 volvo penta a short distance ( probably 300 yards, got pretty hot ) with NO impeller, it was shot, said he was trying to get it to pick up a prime. Anyway after the impeller replacement it runs rough and has little power. Was wondering where to start checking for problems. Thanks for any help

 

[mkast]

Re: overheated 302 runs rough

Try the troubleshooting section in the factory maintenance manual.

 

[SPOONMAN1]

Re: overheated 302 runs rough

Thanks for the input, What I was looking for was common overheating damage that could cause poor performance. I suppose any question on the forum could be answered by looking in the manual.

 

[JustJason]

Re: overheated 302 runs rough

you could have popped a head gasket or warped your heads depending on how bad it was.
Start with a compression test.

 

[SPOONMAN1]

Re: overheated 302 runs rough

Will do. Thanks

 

[Haut Medoc]

Re: overheated 302 runs rough

I would do a (first), vacuum test, (because it is easier) & then go on to a compression test, then a leakdown test if you identify a specific cylinder(s)...
I would check the condition of the plugs/wires.....

 

[SPOONMAN1]

Re: overheated 302 runs rough

Pulled two plugs one was gas fouled, the other was covered with water, will spray cylinders with oil and pull the heads. He said he will have the heads mag fluxed and milled. Will probably put a different cam in it when its apart.

 

[Haut Medoc]

Re: overheated 302 runs rough

Pulled two plugs one was gas fouled, the other was covered with water, will spray cylinders with oil and pull the heads. He said he will have the heads mag fluxed and milled. Will probably put a different cam in it when its apart.

In that case, I would pressure test the cooling system for a leak before I did any teardown, it may be a bad manifold riser....
I would think that before I would blame a head or gasket....
You need to do more diagnostic before teardown, IMHO....

 

[SPOONMAN1]

Re: overheated 302 runs rough

Thanks abunch. Could over heating cause manifold riser failure? Where do I find info on a pressure test on the cooling system. Are there volvo mans in this forum.

 

[SPOONMAN1]

Re: overheated 302 runs rough

To pressure test a cooling sytem how would you cap the exhaust after it leaves the riser?

 

[Haut Medoc]

Re: overheated 302 runs rough

I'm not familiar enough with Volvo, but.....
I would islolate the engine from the manifolds, by blocking off those hoses, & that will tell you if it is a block/head/ intake problem....
You will need to pull the manifolds/risers to test them.....
Look for rust in the exhaust ports, especially towards the rear....
The most common cause of water in cylinders is manifold/riser failure, or the joint between them....
I'm just trying to save you an extensive tear down, when you might not need one.......

 

[SPOONMAN1]

Re: overheated 302 runs rough

Ok, the plan is to remove maifolds & risers and inspect them, then we will do a compression check on each cylinder. I appreciate the info & advice. Thanks again and will update when problem is found.