Cooling problem Ford 302

Discussion in 'Propulsion' started by san, Oct 21, 2004.

  1. san
    Joined: Oct 2004
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    san Junior Member

    Hello everyone out there

    I have a Mercruiser 888 (Ford 302 ~77) with cooling problem. I bought the boat a few months ago and the engine overheated when driving and pulling over 2600 rpm. I cleaned the manifolds that were clogged to 2/3 and after that the engine overheated already at idle.

    The impeller with housing is replaced, new checked thermostat, the water pump on the engine is replaced 2 years ago and all hoses are OK (not clogged or any holes).

    It seems that the circulation through the engine is very poor. The manifolds get warm almost immediately when starting and the engine overheats after a few minutes while the risers is very cold all the time. (On the 888 the circulation goes through the engine, then to the manifolds, back to the thermostat housing and then out through the risers. Not like on many GM engines, through engine, then manifolds and out through risers. Because of this the manifolds can be warm and risers cold on the 888).

    I thought that there must be exhausts pressuring into the cooling system that blocks the circulation through the engine so I tested the manifolds with air pressure but they seemed to be OK. I tore the engine apart convinced that I would find a broken head gasket or head but nothing that can be seen visually.

    There is dirt in the cooling channels of the engine, but a friend told me his engine was almost clogged and worked fine in spite of that. (I have tested to just flush water through the engine block and it works fine).

    I am getting out of clues so if anyone have any suggestions I would be delightful.

    Stefan
     
  2. CarbonKen
    Joined: Oct 2004
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    Location: Southern Calif.

    CarbonKen Junior Member

    Never tear down the engine unless your sure of the problem first !. You could have removed plugs brought cylinders up to TDC making sure your on the compression stroke ( Valves closed ). Now putting an adapter on and air hose so as to fill the cylinder with about 50 psi air pressure . Listen or feel the cylinder holes next to your test hole . If it leaks or you hear hissing . Head gasket is first in line , next is cracked head , or a block . But a block will usually put water in the oil !. Can you close the sytem ?. In other words use exhaust water back into the out drive pump ?. A 55 gallon barrel cut down works pretty good . Now put a nylon sock ( Panty hose works well ) over the raw water pickup on the drive . Place it in the tank put a couple of cans of radiator flush in the tank !. Fire it up and let it run ( You can remove thermostat if you wish prior to proceedure ) or not . Now after it runs for a while ( Make sure temp gauge works correctly ) see how hot it gets ??. 160 , 180 , 200 degrees ? That is the max I would let it get too . let it cool down do it again . See what kind of crap comes out in the tank water !. Pretty soon your manifolds will be pretty clean along with the block . DON'T FORGET to flush with plenty of plain water after you finish !!!. You might want to change Thermostat ( Put a new one in ) and do the water pump at the same time !.
     
  3. san
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    san Junior Member

    Thanks

    What is radiator flush? Isn't it enough to just remove the crap out of engine, manifolds and risers or do you use the radiadtor flush to dissolve crap stocked in the engine?

    I have run the engine on land with the drive in a barrel of water. If I put water into the engine with pressure through a hoose connected to the drive the engine didn't overheat, but when I let the pick up pump in the drive do the job the engine overheated.

    I connected a transparent hoose between the outlet of engine and manifold and saw a lot of ~1 inch big bubbles circulating through the hoose. My thought was that this must be exhausts, but maybe I was wrong. Were came the bubbles from otherwise?

    Stefan
     
  4. CarbonKen
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    CarbonKen Junior Member

    Yes radiator flush cleans out manifolds , block , and water passages in general !. Nylon sock prevents out drive pump impeller from picking the flushed junk up and going back over the pickup pump impeller , Or Drive impeller ! . If your not experiencing over heating with hose attached to the out drive ( I'll assume your using ears via a water hose placed over the out drive water inlets ) BECAREFULL NOT to over pressurize the intake water !!!!!!!!!. Those out drive water pickup pumps are desined to DRAW water from a lake ,river ocean what ever the raw water source !!!!!!. NOT having excess water forced through them , this can damage the impeller's fingers !!. I have seen cases where it actually flipped them in the opposite direction before they broke off and ended up plugging a water passage !. In old brittle impellers this is almost a given !. Did you not say you had put or some one had replaced the water pump in the out drive ?. If so did they get the water pickup tube rubber ring on correctly ?. There is a water guide tube on top of the water pump housing in the lower out drive unit !. It connects via a rubber slip type grommet to the upper water tube !!. You have to undo the lower drive unit to check it !!!. This is a common error which I have seen several ( Proffesional mechanics messup to) being in a hurry or not having a new grommet or using the old cracked one . Plain and simple if your water pickup pump on the out drive is not sealed or something is not installed correctly in the water pump it's self , your doomed from the start !. To check this use tub or tank to draw water from , disconnect water inlet hose either at the tramson helmet or shield area or further forward if access allows. Disconnect the hose put it in a gallon or so container then start your engine . You had better see a good deal of water coming in at this point . If not THAT IS WHERE YOUR PROBLEM IS !!. If not do what I recommended previously , you have little to lose at this point !. Good luck ...
     
  5. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If you have power steering, check the cooler. Often when the impeller breaks, pieces of rubber will clog it. Also, have you tested the thermostat and made sure it is the correct one? It should have weep holes.
     
  6. san
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    san Junior Member

    Gonzo
    I don't have powersteering, but thanks anyway. However, I haven't checked the hose between outdrive and stern for possible pieces. I will do that. The termostat is replaced with new (original) one and also checked, no problems. I have run without termostat as well, but no difference.

    CarbonKen
    I replaced the water pickup pump myself. There were 2 sealings in the impeller housing kit and I aint sure which one you mean, one is to be put into the pump house (to seal against watertube from upper drive unit) with the water tube guide assembled above it, and one with rectangular cross section. I asked the store keeper were the later should be placed and he said that it should be positioned on the outside of the water tube guide and pushed down the guide to seal against the pump house. Is this right? I cant see the purpose of it.

    I have tested to run the engine with water inlet hose (on engine) disconnected. At idle it poors water out of the hose without any height of the waterbeam, and when giving a little throttle it rises rapidly. A friend has a Ford 460 and according to his manual the water beam at idle should be about 4 inch high, but that is a larger engine.
     
  7. gonzo
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    gonzo Senior Member

    Re-reading your first question, it seems as if the manifolds or the thermostat housing are clogged. The overall water flow is good if the risers stay cool. It seems that the problem is not the volume of water but where it flows. One test is to disconnect hoses with the engine running(watch out for belts) and verify that water flows out of the thermostat housing. If it does then check it flows through the manifolds.
     
  8. san
    Joined: Oct 2004
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    san Junior Member

    I have tested that with no obvious result because every flow connects back to the thermostat housing on 888 engine. It isn't very logical that all flows (feeding water, flow to engine, flow from engine, flow from exhaust manifolds and flow out on the risers) are in connection with each other. It feels like the different pressures will work against each other. When I disconnect the hose between outlet from engine to exhaust manifold you will have water flows from both engine and manifold.

    It is because of this that I tested with transparent hoses as seen at beginning of this thread. Also because of this test that I tore the engine apart when I saw air bubbles in the flow between engine and manifold.

    The engine looks to be in really excellent condition with, but the thermostat housing is very rusty. It is hard to describe this, but when the cooling water comes out from the engine into the thermostat housing, it is separated to go to both manifolds. The wall that the engine flow hits in the thermostat housing was very rusty and probably very worn from many years of use and it was a hole in it. I thought that this must be the problem, pressure from pick up pump and the pressure from engine water pump working against each other, so I plugged the hole. After that the engine overheated even faster.

    I don't think this engine is build by Mercruiser, but Murphy.

    Exactly like you said Gonzo, the problem isn't the feeding of water, but the cirkulation through the engine, and it feels like exhausts pressuring in somewhere and working against the flow through engine could be it. I have tested the manifolds with air pressure without leaks, but maybe I have to test at higher temperature (simulate operating temperature). There aren't any visible cracks in the heads, but maybe I must look deeper into this as well.

    This is very strange, and if you have any ideas left, please let me know.

    Stefan
     
  9. gonzo
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    gonzo Senior Member

    We cal it the octopuss setup. The water flows from the manifold into the risers from the bottom through restriction holes in the gasket. For proper flow the manifolds need to be clean and free of scale rust.
     
  10. san
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    san Junior Member

    Yes, there are restriction holes between manifolds and risers with about 1 mm diameter. What purpose with those tiny holes? What happens if they are clogged? When using closed cooling system on the 888, the manifolds as well are included, then you don't use the tiny holes?

    Stefan
     
  11. gonzo
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    gonzo Senior Member

    They will restrict flow and probably overheat the engine.
     
  12. san
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    san Junior Member

    Is it possible that theese holes are to bleed the air out of the manifolds when engine has been out of water, and if the holes are plugged the air will stop the water circulation?

    Any thougts?

    Stefan
     
  13. gonzo
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    gonzo Senior Member

    Yes, if there is air in the block/manifolds, the circulation pump will cavitate. Air also creates hot spots.
     
  14. Brad D
    Joined: Aug 2005
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    Location: Chicago

    Brad D New Member

    help

    Are you guys talking about the tiny hole in each plate that sits between the riser and the manifold? I have the same engine with the 888 and am having problems with overheating. Last summer i took the risers off cause of a leak and when i put them back on i used gasket maker along with the gaskets. If that small hole is clogged with gasket maker could that be my problem? Should there be more than 1 hole on each plate and what are these plates for?


    Brad
     

  15. gonzo
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    gonzo Senior Member

    They are restrictor plates. The back pressure keeps the engine full of water without air pockets.
     
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