Cooling problem Ford 302

[san]

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

[CarbonKen]

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 !.

[san]

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

[CarbonKen]

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 ...

[gonzo]

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.

[san]

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.

[gonzo]

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.

[san]

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

[gonzo]

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.

[san]

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

[gonzo]

They will restrict flow and probably overheat the engine.

[san]

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

[gonzo]

Yes, if there is air in the block/manifolds, the circulation pump will cavitate. Air also creates hot spots.

[Brad D]

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

[gonzo]

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

[Frosty]

You say it does'nt overheat if you run the engine on land with the leg in a barrel of water and feed the engine with a hose but will overheat if you let the pump in the leg do the job.
Gotta be the pump or the feed from the pump????

I would pull the pump out again and check it out. I would check to see if the brass centre bush of the impellor had not lost its bond with the rubber impellor. Make sure you twist in the impellor blades the right way to rotation, they should right themselves but!! maybe it tried to do that and bust the bond,--could have been an old impellor ie past its shelf life.

[san]

I pulled out the engine, cleaned and inspected it (lots of dirt). The head gaskets didn't look good, the "metal rings" around the cylinders had corroded and the gaskets had separated so compression should have been able to get into the cooling system. I was happy and thought this was the problem. The heads are now milled. No visible cracks. Everything on the upper half of the engine is inspected and looks good now. I've replaced the exhaust manifolds and risers since they didn't look OK.

Now I am able to run the boat at about 3200 rpm without any problems. If I pull full throttle it works fine for about 20 seconds with temp gauge at 150 F but then instentiously the temp rises to maximum.

Is it needed to pull the heads with tourque wrench after running the engine warm once? It seems to me that it must be exhausts in the cooling system since the temperature rised so quickly. Can a lean running engine behave like this? I ask this since after my restoration of the engine when I gave full throttle the rpm went up and down, like it didn't get enough fuel. This behaviour disappeared after the first run.

San

[gonzo]

Modern gaskets don't need to be retorqued. A lean mixture will make the engine heat up, but usually not that fast. Do you have access to an infrared thermometer?

[san]

Thats a smart idea. I suppose you mean that you would find the heating spot making the problem? Am I able to find for example a crack in a head with this method?

[travis912]

I am having the same problem with my 302 marine engine i took it to a boat place to be worked on becaues it was over heating it is a new engine the boat place put in they took manfolds off and found the restrictor plates in it and said that was the problem so they took them out i ran it and it did the same thing overheated so i changed the water pump on engine did not make much difference changed thermostat still the same so wondering if the restrictor plates need to be back in. My restrictor plates only had a pin hole in it LET ME KNOW WHAT TO DO !!!!!!!!

[san]

If you have the "octopus" cooling system where water from exhaust manifolds goes back to thermostat housing and then out through the risers you must have the restrictor plates. The pin holes are there to let air out of manifolds directly to risers (for instance when the boat has been on land and engine is drained of water), but water flow should go back to thermostat housing.

My problem was not the engine, but a gasket in the drive. My exhausts goes through the drive and the gasket between plastic plate you put the impeller house on and drive was ruined. With this the impeller tried to pick up water but with more throttle the pressure from exhausts overtake the pick up of water and the engine was filled up with gases. With less throttle the engine was able to get rid of gases but the more throttle the bigger the gas bubble in intake manifold became with less circulation of water. This was the reason why the temp gage rise that suddenly. When gas bubble grew and got to temp sensor the needle rised in a few seconds.

This was what I did to find the problem and what I recommend you to do. Put a transparent hoose between drive and engine (that is before cooling water gets into engine) and make sure you dont have bubbles of air in water when running engine. If you have bubbles the problem isn't in the engine but the problem is before the engine. (I have asked dozens of experts but no one has even mentioned something like this)

I wish you all luck and hope this is your problem as well. Easy and cheap to fix.
Stefan

[travis912]

hello again I took one of the hose off that goes to the thermostat then to the exhaust manfold and there seems to be alot of exhaust fumes coming out the hose could this be caused from a crack in a exhaust manfold. engine runs fine when not being ran at high speeds over heats about 2 min after you get out of the water.

[gonzo]

There should be a lot of water coming out of the hose.

[san]

Do as I told you. Put transparent hooses both before and efter engine and take your boat for a run. If you only have bubbles getting out of engine, then you have a crack in one head, blown head gasket or leak in exhaust manifold. Do your spark plugs corrode (leak of water)? Is the engine easy to start? As written earlier in this thread you can check for cracks in heads or blown gaskets with air pressure. Exhaust manifolds can be tested in same way with air pressure. Risers are a little more tricky to check due to water and exhaust getting together inside riser.

[travis912]

if crack in head or blown head gasket shouldnt the engine run like crap or mis

[san]

Doesn't have to do that and depends on how big crack you have. What happens is that exhausts from combustion chamber is pushed into cooling system and circulation stops. If you have a big crack or leak then water can get into the cylinder and either fill up the cylinder with water or corrode in cylinder. Then the engine wont run on startengine or becomes hard to start. That's why I asked about if your boat is hard started. If you have a small crack neither of this have to happen. The crack grows and let exhausts through when engine becomes warm but doesn't make any error when engine is cold. Easiest way is to check with the transparent hooses to surround the problem.

[Frosty]

Hang on a minute guys, i think your going down the wrong road. When you took the hose off the thermostat housing you say a lot of exhaust was coming out of the pipe, you now assume that the exhaust is cracked. Well its never going to be cracked big enough for exhaust to be coming out.
What you've got is exhaust pressure coming back throught he exhaust injection holes back up through the manifold and out through the cooling system simply because it the easiest way to go because you have the pipe off!!!!--- if im following your story correctly?
Now Gonzo says there should be a lot of water coming out of the hose, he is talking about the hose from the thermostat, it depends on wich end of the hose you are looking at. There should be alot of water coming out of the thermostat hose going down to your manifold as gonzo says. if you dont you have weak pump pressure. Pheeeeeww

I am assuming you've checked the thermostat or take it out ????

[gonzo]

You are right, it depends on which hose end it is. If you mean the end from the manifold, it will be dry and exhaust gas will come out.

[travis912]

I have the log style exhausts manfolds with end risers there are two hoses on the end risers a top hose and a bottom hose the top hoses are blowing exhausts back to the thermostat housing which is blowing exhaust into the engine could this mean that the riser could be cracked or busted on the inside

[san]

Maybe I'm misunderstanding what you mean. Attached is log style manifold and riser (poor quality). On this you have one hoose on riser and one hoose directly below riser on exhaust manifold.

When engine is cold most water goes directly through top hoose on riser. When engine becomes warm water goes through engine, to manifolds, back to thermostat housing via lower hoose on manifold directly below riser and then out through upper hoose on riser.

I have also tried doing what you've done on my engine with this setup, and there should come water whatever hoose you pull. The easiest way for exhausts is through the stern if everything is in order.

If you pull the top hoose on riser which should drain water FROM engine and you get exhausts from riser (does water come from engine in this case?), then there is a plug somewhere that makes easiest way for exhausts through top hoose on riser. Can be the flip flops in lower part of Y-tube.

[l_boyle]

Okay there ya goes, I would of say.. Pop out all of soft plugs on the both sides of the block, and there more at rear of the block also, and take the pressure washer, blow the gunk out that you see bulding up inside of there..

[travis912]

what do the filp flops do

[san]

On Doug Russell they call it "shutter-water". It's a non return valve that keeps water from getting into engine via exhausts when you for instance rapidly go from high speed to zero.

[Brad D]

I have a Mercrusier 302 - 888 and had issues with overheating 2 seasons ago. I replaced the original log style manifolds this past summer with a universal center riser style. The only thing is the gaskets and restrictor plates that came with the setup didn't have holes to allow gases to escape. Due to weather I was only able to start the boat in the driveway with the hose attached(everything seemed fine). Before i head out on the water to see what is going on with the overheating issue...Do i need to drill little holes to allow steam to get out or is it going to be ok without them? i don't want to add another problem to the overheating issue.

i still need to replace the impeller and check the thermostat.

[gonzo]

Do you have separate hoses for the manifold and the riser?

[Brad D]

I still have the octopus thermostat housing, so i have a hose going into the manifold and one coming out. I also have a hose running into the riser.

[san]

Shouldn't cooling water on center rise manifolds go directly out through risers instead of back to thermostat housing and then out through risers? DO you have the right gaskets?

I would test the boat in water like it is and if it doesn't work out I would look into replacing the gaskets so cooling water run directly from manifolds to risers. With this you would have to replace the octopus thermostat housing with a new one. (Maybe you can plug the 2 inner/under outlets on octopus housing that comes directly from engine. I think this would work as well.)

I would not drill holes in gaskets unless I was sure that I got the wrong parts.

[Brad D]

This setup is exactly the same as the log style only the riser is in the center and not at the end. All the hoses that were on the log style setup attach at the same spots on the new manifold and risers. The only thing is there wasn't a restrictor plate with a little hole included, only 2 types of gaskets. 1 had no holes just a flat plate gasket, the other was a pass thru gasket holes around the edge. Both styles are attached (not the exact same but close)

I installed the plate gasket, i guess the only way to test it is to run the boat in water this summer.

[metalman]

I Had The Same Problem Changed Impellor Few Times Didnt Work Had To Change All Parts In Pump Located In Leg The Most Important Pc Was The Plate On The Back Of The Pump