closed cooling issue merc350i.o alpha1

[freeone]

hello all, i have a 84 merc 350i/o with alpha1 and closed cooling system.
problem loosing coolant from overflow reservoir(empty) into bilge, engine never overheated steady temps at 160-180.
parts replaced new t stat 160 degree, pressure cap 14psi, od water pump, engine water pump, exhaust manifolds and risers about 30hrs ago.
ignition timing set at 8btc idles at 650, new plugs wires and rotor thunderbolt iv ignition.
suspicion pressure cap psi too low. any ideas?
question can i run a higher psi like 16? would that cause the cooling system to over pressurize?
thanks for your time and replies.

 

[FreeBeeTony]

Re: closed cooling issue merc350i.o alpha1

I had a similar issue once..........it was a failed gasket between the manifold and riser.

Are your manifolds FWC'd?

Is the antifreeze diluted? Could be mixing with the raw water side and overflowing.........if the manifolds aren't on the fresh water side.........maybe the heat exchanger has an issue.

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

I had a similar issue once..........it was a failed gasket between the manifold and riser.

Are your manifolds FWC'd?

Is the antifreeze diluted? Could be mixing with the raw water side and overflowing.........if the manifolds aren't on the fresh water side.........maybe the heat exchanger has an issue.

dont know what that is "FWC'd"
manifolds are coolant the risers are fresh water, heat exhchanger got pressure tested and cleaned when i replaced the manifolds and risers.
i will check the riser gaskets.

 

[FreeBeeTony]

Re: closed cooling issue merc350i.o alpha1

FWC'd = Fresh Water Cooled

 

[QC]

Re: closed cooling issue merc350i.o alpha1

If everything you say is right, then it sounds like a head gasket or worse . . .

 

[FreeBeeTony]

Re: closed cooling issue merc350i.o alpha1

How/why would/could a bad head gasket cause the fresh water side to overflow?

 

[searay3]

Re: closed cooling issue merc350i.o alpha1

Blown headgasket can pump air into the freshwater side. Pressure check the freshwater side. If it won't hold pressure and you can't see a leak, chances are it's internal of the motor...

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

How/why would/could a bad head gasket cause the fresh water side to overflow?

fresh water side not overflowing, the coolant reservoir thats connected to the heat exhcanger is overflowing/empying. only two places where coolant and fresh water are in proximity is the heat exchanger and the riser(fresh)/manifold(coolant).

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

If everything you say is right, then it sounds like a head gasket or worse . . .

head gasket, easy fix... what can be worse?

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

to explain better here is how my system is plumbed
sea water side: water picked up through the outdrive pumped to bottom inlet of heat exchanger(HE), runs through the HE cooling the coolant out the to top outlets to the risers and ou the exhoust.
fresh water cooling: after the coolant is cooled in the HE it goes to the motor WP in the block/head\intake through the tstat to the top of exhaust manifolds out the bottom back to the top two inlets on the HE and the cycle continues. just like a cars radiator the HE has a tube leading from the fill neck/ radiator cap housing to a overflow reservoir.

 

[chuck in WA]

Re: closed cooling issue merc350i.o alpha1

Freeone, I think you're getting terms confused.

The freshwater side IS the coolant/antifreeze side (hence the name freshwater cooling (FWC) or closed cooling system).

Seawater side = the water coming from the ocean/lake, circulating through the heat exchanger, then back overboard through the manifold/elbow(s).

I'll certainly agree that the terms are confusing. I sure wouldn't want to drink any of the "fresh" water cooling my engine!

 

[FreeBeeTony]

Re: closed cooling issue merc350i.o alpha1

closed cooling: after the coolant is cooled in the HE it goes to the motor WP in the block/head\intake through the tstat to the top of exhaust manifolds out the bottom back to the top two inlets on the HE and the cycle continues. just like a cars radiator the HE has a tube leading from the fill neck/ radiator cap housing to a overflow reservoir.

The routing should be that after the tstat it should go to the BOTTOM of the manifolds and out the top back to the HE.........don't think this is your problem but I don't think it's correct either.

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

sorry for the term confusion, ive edited the post to read correctly.

and it is going to the bottom of the exhaust manifold from tstat to topto HE.

so far im going to check the riser manifold sperator gasket and do a leakdown test. havent done one in a while can someone steer me in the right direction. thanx.
also been reding manual on adults only finally found the specs on the pressure cap(14psi) tstat should be 143degrees, im running a 160 can that cause the overflow of the reservoir? being higher temp more pressure build up before it opens? Don S?

 

[FreeBeeTony]

Re: closed cooling issue merc350i.o alpha1

1st thing I would do I'd do is presure test the closed cooling side of the HE.

just remove the cap and connect a presure tester.......you can rent one at Autozone for nothing...........just leave a refundable deposit.

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

going to do pressure test on the cooling system and a leakdown test, will post results tomorow. Again thank you all for your help!

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

taking me longer than i thought, have to remove exhaust manifolds to be able to do a proper leakdown test. cant reach the plugs.

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

did comp test all was well untill got to cylinder6 took the plug off coolant came pooring out. so i took the head off have coolant in cylinder. where do i go from here? do i replace the head gasket and assemble? or is there something else i should look for? couldnt inspect the head gasket came apart during disassembly. Don S. any input?

 

[Salt Life]

Re: closed cooling issue merc350i.o alpha1

I had a problem of loosing coolant, not overflowing. I've got the same setup, closed cooling system, 350 I/O with the Alpha One. My problem was the gaskets between the exhaust manifold and riser was allowing coolant to leak inside to the exhaust. I could smell and see the steam when I ran it on the muffs. Was there coolant in the bottom of your exhaust manifolds when you took it all apart? And what was your compression in #6?

 

[freeone]

Re: closed cooling issue merc350i.o alpha1

I had a problem of loosing coolant, not overflowing. I've got the same setup, closed cooling system, 350 I/O with the Alpha One. My problem was the gaskets between the exhaust manifold and riser was allowing coolant to leak inside to the exhaust. I could smell and see the steam when I ran it on the muffs.

Could that cause coolant to go into the cylinder?

 

[Salt Life]

Re: closed cooling issue merc350i.o alpha1

You bet! I had a low compression problem in two cylinders, took it all apart to find bad valves. A valve job later and everything running great about 10 hrs after the job I decided to do a compression test on the engine one morning to see how things were holding up. I pulled # 5 and # 6 spark plugs out to find gut wrenching coolant on the plugs. Well I figured I screwed up the head gaskets and was getting ready to take it all apart again. As soon as I took the risers off I saw coolant sitting in the bottom of the manifolds. I knew then that the gaskets were not sealing. If the coolant fills up enough and your exhaust valves happen to be open the coolant will leak into the cylinder. I never had the problem of the overfill leaking out though, I just had an underpower and overheating problem. So anyways come to find out the gasket surface for the manifolds was warped from corosion over time and it wouldn't seal properly. I also have a 13 psi cap and my t-stat is 160. WOT temp runs around 190.