manifolds or risers???

[fishingman220]

I have a 96 merc 5.7 it has center rise manifolds, well i am in the process of rebuilding the motor due to water getting into the exhaust and working its way into the cylinders. i have thru the hub exhaust, good flappers, and ran fine the last time it was out. i have a complete closed cooling system, so correct me if i am wrong, but antifreeze is in the manifolds and raw water is in the risers. so how would water get down into the maifolds and into the motor? it only got into the # 3,5,and7 cylinders. it looked like antifreeze in the cylinders, but it could have been anything cause i didnt see it untill i pulled the heads and antifreeze went everywhere. but as far as i know antifreeze wont rust stuff. any help would be greatly appreceated. i bought new manifolds, but now i thinking i didnt need them

 

[chris0061]

Re: manifolds or risers???

usually the problem is in the riser to manifold gaskets or a cracked water passage in the exhaust manifold. I just descovered water in my 8/6 cyl and just pulled the riser off and found the gaskets to be good so now I have to get a mirror and look inside and see if I can see any cracks. Your's is a closed cooling so I'm guessing your new manifolds will fix the problem.

 

[Bt Doctur]

Re: manifolds or risers???

Water can only come from a bad riser to gasket seal, or a bad riser on a fully closed system. Only other way is up the exaust system.Shutting off in gear, large wave hitting the sterm,etc.

 

[fishingman220]

Re: manifolds or risers???

so, when i put it back together, with new manifolds, what is the best way to check and see if water is comming in?? or how can you check the risers?

 

[Don S]

Re: manifolds or risers???

With a NEW engine, and new manifold, put on new risers or you are just begging to loose another engine.

 

[fishingman220]

Re: manifolds or risers???

yeah thats what i thought. i am out of funds, i guess i will just have to wait to get it running.

 

[Apollo75]

Re: manifolds or risers???

Hello;

I agree with Don S --- need new risers if anything. I do not see manifolds ever wearing out on a closed cooling system filled with GOOD anti-freeze. Parts should look like new after 30-years.

Well, regular maintenance change of anti-freeze every two years and not getting the manifolds hot enough to crack, etc, etc.

Good anti-freeze with rust inhibitors will not rust but the water evaporates and it turns into some kind of goo. Anti-freeze in the oil --- usually working it's way past the rings will wreck bearings. I have seen a lot of spun bearings because of it.

If it was a intake manifold or head gasket leak --- any slow leak into a cylinder -- that piston and head chamber should be very clean inside compared to the other cylinders. An easy way to check for a slow leak.

OFM

 

[fishingman220]

Re: manifolds or risers???

you can see in the manifold, that is the way the water came in. so i guess it had to be either the gasket or riser, how do risers go bad?

 

[Apollo75]

Re: manifolds or risers???

Hello Fishingman220;

They either rust until a spot opens up and they leak or they crack from getting hot or from old age as cycling from cold to hot and back again causes fatigue cracks. Most are replaced because they get plugged with rust and scale deposits and slow the flow of cooling water and the engine runs hot.

Usually a riser is a substantial piece of cast iron and fairly thick. I would make a pressure tester --- just block off all the holes and see if it holds pressure --- 10 -lbs of pressure for 15-minutes.

They can be cleaned out --- various methods on the forums --- and used for many years --- more years usually running in fresh water.

There is not much water pressure when they are in normal use so they last a long time with proper maintenance. They should be removed and inspected every 2-to-3 years of operation --- depending on circumstances referring to time --- and "cleaned out".

OFM

 

[fishingman220]

Re: manifolds or risers???

i looked alittle closer and on the side there was water i think i see a small spot where water could have run through it looks like a small rust trail through the gasket

 

[Don S]

Re: manifolds or risers???

Cleaning manifolds or risers is not a good thing to do. If they plug up, it's from the rust and corrosion developed inside the manifolds and risers. If you clean them, you loose your early warning system that they need replaced.

 

[fishingman220]

Re: manifolds or risers???

the inside was a real bright orange and a few flakes but no build up, they look good other than that

 

[Don S]

Re: manifolds or risers???

Post a picture of the cleaned gasket surface of the risers.

 

[fishingman220]

Re: manifolds or risers???

i will, i am getting drug to the grocery store, then i will get some pics on here

 

[Apollo75]

Re: manifolds or risers???

Hello;

Well, we are not repairing the Shuttle with unlimited funds here where we can replace everything that has a season of wear on it.

I agree that a good cleaning of these parts and if they are heavily rusted sent in to a radiator shop or hot tanked, etc. Parts that are raw water cooled should be given a through visual inspection for deep pitting, etc. And then pressure tested!

I happen to think an engine block has more surface area to rust on the inside and most of these rust flakes/rust particles come from the block and get deposited or stuck in a small/smaller passage and restrict the water flow.

In a closed cooling system this is not a factor and the only rust you will see in a riser is from the riser if nothing else in the raw water part is rusting away.

At any time one of my pistons could come through the thin cylinder wall of my 34-year old 302. Or a pin sized hole could allow water to get in somewhere.

It is a judgement call and we all make them. Consider all the good advice in the forums and make your own call.

OFM

 

[fishingman220]

Re: manifolds or risers???

ok here are some pictures, first one is without gasket and second one is after cleaned up surface with wire wheel

 

[Don S]

Re: manifolds or risers???

Lots of glare on the bottom half, and not being able to look at it for real makes it hard to tell.
I did circle one area that could be a problem. Is it leftover gasket material or has the metal of the riser turned to a black hard carbon substance. When they do, they are junk.
The surface also has to be flat, and the proper gaskets used to make a proper seal

 

[fishingman220]

Re: manifolds or risers???

i will look at it tomorrow and get back to you, and try and get a better picture, thanks

 

[Apollo75]

Re: manifolds or risers???

Take a flat file and run it across the whole surface area to clean it up --- there is a little area that is pitted above also. It takes a few minutes to clean up the whole surface area but you should be able to get it nice and flat again.

Do the same thing with the thermostat housings when they get a little pitted. A good gasket will compress and seal it. Use a good non hardening gasket sealer to keep pitting in check. I like copper coat myself for most engine parts and even spray it on head gaskets.

OFM