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Did the machine shop pressure check and surface the heads?

Let me add a little something here.

Putting aluminum heads onto an engine presents problems that require more frequent maintenance. If the coolant is not changed frequently (minimum every two years) it will turn acidic and start eating things like head gaskets and aluminum material.

There are special head gaskets to use (graphite coated and impregnated) to allow for the different expansion rates for the dissimilar materials (iron-aluminum) to slide on one another. Did you check the machined surface of the lower intake for damage?

You need to pressurize the system and see if it holds overnite. Start it and allow it to warm up and see how much pressure is produced.

Do the leaking exhaust gas test again. There is an internal leak somewhere most likely.

You are not using cheap a$$ box store CHI-COM parts are you?
 

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Here is something else to speculate about until we find out what the real temp of the engine is. You stated in your first post that you had the water pump off, but that it seemed fine. Did you actually check that the impeller was tight on the shaft? I have seen impellers that were loose and under load of moving the water, would not spin at shaft speed causing the water pump to not move enough water. Not a very likely cause, but one none the less. And are you sure all of the air has been bled out of the engine?
 

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Discussion Starter #27
Hi All, a quick update. I did a long update last night, hit submit reply and it just wiped it, so i gave up.
Now try again, Have rechecked everything with the heads guys , as expected , they did everything right. I'm ruling out the heads for now.
Today went to a radiator joint they check the whole system and cleared thermostat, water pump and radiator, but came up with some interesting findings....
 

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Discussion Starter #28
The radiator shop, iniatially refilled the radiator(as it overheated and dropped all its coolant upon arrival), then let it run for a few minutes at idle with the radiator cap off,while watching the temp gauge rise away! Then shut the engine off and ....WOOOFF. A big gush of water came back out the radiator. the guy said thermo is block , remove it.
Then i removed the thermostat and drove it again. Sure enough, still overheating. I left the truck with the guy and he ran a further series of tests. The results came back - water pump, thermostat, radiator fine. the engine is overheating at the back of the block ( front seems fine). He suspects some sort of blockage, maybe head gaskets on backwards. I know this is not the case, but do suspect some blockage in the rear of the block.....
 

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Discussion Starter #29
The guy also added in that the vehicle is going from cold to normal operating temperature and continuing to rise and also pressurising the radiator. (sounds like a head gasket??). the radiator is showing a lot of bubbles coming through.

Now I'm stumped!! Bare in mind, the symtoms have not changed in since i bought the truck 3 weeks ago. Since then new radiator, thermostat , water pump off, fully reconditioned heads, including crack testing, facing etc.. Head gaskets are definately on the right way.

Any suggestions??
 

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Discussion Starter #30
Also like to say, the radiator guy did not do a TK test (exhaust gases in coolant). I want to try to do that tomorrow.

I'm thinking remove core plugs and poke around the block to try to dis lodge some sort of blockage. Have heard of people leaving old core plugs in the block and having such issues. This would not explain the bubbles in the radiator though???

Finally can someone please tell me the reason you would need to know the EXACT temperature the car is overheating at?? I can't see the point! Isn't the fact that it is overheating at all, enough to say there is a fault?

PLEASE everyone keep posting
Thanks again
Galman
 

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Take the heads back off and check the block for cracks, also check the surface of the block.

Bubbles mean combustion gasses are getting into the cooling system, which to me, does not mean a blockage, but a failure of a seal or gasket.

The reason I inquired about Temp that it overheated at is simply because sometimes they're bad and you're not overheating at all. This is not the case after reading your last couple posts. You said Boiling out, which you failed to mention in all of your previous posts.

I say a cracked head or failed head gasket... again....
 

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Discussion Starter #32
Thanks FE.

Do you think, maybe a unseen blockage causing it to overheat and blow the head gasket again?? I'm confident in my skills to clean the block face and reinstall the heads. I dont think I did anything wrong.

I more piece of information (sorry only witing it as it comes to me), while cleaning the deck surfaces, I blew out any lose gasket bits with compressed air. I noticed that the coolant level in the rear water jackets of the block was still at deck height. I thought this would have already drained out as lower radiator hose was off. Didnt think to much of it at the time but now I'm thinking did it indicate a blockage in the back of the block in this area?

What do you think?
 

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The coolant passages likely retain a little smudgy amount rust flakes and grime but having coolant in the rear at the level of the deck is normal.

I don't know if the gasket is blown again or if the deck has an inconsistency that was not noticed or if you have a cracked cylinder wall, or if the machinists screwed when they Pressure tested your aluminum heads.

If it was as simple as blockage in the rear of the block you might find evidence of it when you take of the heads again. Teh gaskets will be as perfect as the day you put them in but will have had the "crush" put to them from the tightening sequence, if there is an error you will be able to see it in the gasket surface possibly. Remove the heads carefully.

I wish you luck!
 

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Discussion Starter #34
Hi All,
Another update.
I removed the heads AGAIN this weekend and found... nothing! Heads appear great, gaskets were fine and I cant find any signs of a crack in the cylinders. Also checked all water galleries and no problem there- actually cleaner then last time with all the effort put in. I suppose the next step is to take the block out anyway, and see if the machine shop can fault it?? Failling that, I cant think what to try next!

Cheers
 

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Discussion Starter #35
This must be getting TOO technical for you guys out there in Fordmuscle land, oh well I'll keep you updated anyway.

Spoke to the machine shop guy today - he suggested check to piston heght in relation to the deck. Apparently it should be 1mm below deck height. So I checked it when I got home. Pistons are 1mm ABOVE deck height! Too much compression??!!

Apprently this can be somewhat unnoticable, while running in a heavy vehicle (didint have any signs of pinging etc..), but can cause the exact symtoms. Especially as No 7 cylinder (the one that seems to be overheating ) has the worst cooling on a 351 windsor block.

Any thoughts??
 

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Discussion Starter #36
Thicker head gasket??
 

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Over heating issues are not that hard to diagnose. For what you have spent on pulling heads you could have bought a block tester kit to help confirm whether or not combustion gases are getting into the coolant. With any over heating issue you need to make sure the main players are in good working condition, thermostat (and installed correctly), radiaitor, air flow and water pump. If this is a vehicle you dont know much history about then you need to consider that the radiator may have been swapped with a smaller one. Another issue that can cause over heating is ignition timing. Make sure its set correctly. If the top radiator hose stays cool and water is being forced out the radiator that would indicate that water isnt flowing because of the thermostat or water pump. Make sure you have the correct rotation water pump. If water isnt flowing the top hose will not get hot and water pressure will flow backwards through the water pump and you will have a hard over flow from the radiator. If water is flowing you can see this through the radiator cap hole.
 

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This must be getting TOO technical for you guys out there in Fordmuscle land, oh well I'll keep you updated anyway.

Spoke to the machine shop guy today - he suggested check to piston heght in relation to the deck. Apparently it should be 1mm below deck height. So I checked it when I got home. Pistons are 1mm ABOVE deck height! Too much compression??!!

Apprently this can be somewhat unnoticable, while running in a heavy vehicle (didint have any signs of pinging etc..), but can cause the exact symtoms. Especially as No 7 cylinder (the one that seems to be overheating ) has the worst cooling on a 351 windsor block.

Any thoughts??
got a low tech question for you galman. how much air psi do I need to ADD to my tires ? must be correct to 1/10 lbs.
 

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Discussion Starter #39
Hi guys,

Arnoldtx- All things you have suggested have been carried out many times and definatley eliminated. I think i looking for something out of the ordinary here.
DanH- your insightful reply is as much as I would expect from you. Keep it up TOOL!!
 

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Galman,

I think your machine shop has sent you on a wild goose chase. The piston deck height will have nothing to do with your overheating issue. Many of us build engines with the pistons above the deck to get a good quench. You know it is too much if the piston is hitting the head!

DanH can be a little abrasive at times (OK, very abrasive and often), but I think his point is that deck height has noting at all to do with your overheat issues. Not even close.

Overheating has a simple cause. Always.

Did you pressure test the system? Did you check for combustion gasses in the coolant? Did you confirm that the thermostat is working and installed correctly? Did you confirm that the water pump is spinning in the proper direction? Did you confirm that the head gaskets were installed correctly (holes toward the rear)?

If the answer to any of the above questions is "no", then you just haven't checked everything yet. Or worse, you are looking in the wrong place!
 
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