4.6 Engine overheating

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paulblake427

New Member
Posts
9
Had vehicle (1996, 70K miles original) for 1 year so quite familier with 4.6 overheating issues. Currently vehicle off road due recent extreme overheating problems, no oil in water, no hose leaks, losing water out of header tank when hot, no bubbles when just started cold.
Replaced thermo stat, same. Removed water pump; looks ok but for the life of me I cannot see how the unit works as the impeller looks like it is deigned to push water through the block and not through the large bottom hose to the thermo stat (anti clock wise rotation looking at the front of the vehicle). I asked an engineering friend and he agrees, looked on web and found a you tube video which whowed the impeller the same as mine !!!!! Anybody noticed this before ? Comments please.
 
it is designed to push water through both banks of the block equally hence the shape ,earlier pre-serpentne belt engines such as 3.5 and 3.9 had different design and tended to cooldrivers side bank more than passenger side ,and that was side more prone to crack with those early 3.9s , obviously you have to check all posibilities like if rad is hot all over the entire core when engine upto temp but could easily be cracked block ,crack opens up when engine warms
 
Thanks and understood about cracked block, so water movement is through the block and down to the Thermo stat via a smaller dia hose, similar to the heater hoses ?
 
hth
cooling96YM.jpg
 
Many thanks to you both, I will do further investigation this weekend. Seems a shame to scrap the vehicle if it is a cracked block, as most everything works well !!
 
paulblake427 said:
Many thanks to you both, I will do further investigation this weekend. Seems a shame to scrap the vehicle if it is a cracked block, as most everything works well !!
Click to expand...

Ok but don't jump to any conclusions... My cracked block manifested itself when warmed up only (as mentioned by James), but I did have over pressure and coolant loss from the expansion tank (you said you had no collant loss from here). The temp gauge would jump from middle to red very quickly and back again. Anyway it's been spot on since short block replacement. Good luck with it :)
 
qwertz said:
Please be nice ( I did search),

what is called a SHORT block?

Thank you.
Click to expand...

Bottom half of engine is a short engine, never heard them called a short block to be honest. Think they mean a short engine. Block, crank, pistons, cam Etc, no heads or ancillaries.
 
A short block is a term used when you only buy the cylinder block complete with crank, pistons etc....basically an engine minus the heads and ancillary bits and bobs like the alternator and timing gear etc etc
 
OK, thanks for further info. However did fit water pump back on and only filled the engine with water by way as a test to see if there was water movement when the engine was running; there wasn't. I.E I disconnected the heater hose in the engine compartment point and left open and pointed it up, then removed the top hose completely, filled with water (I know there would be a small feed though from the thermo housing piping). However with the water visible from the engine top hose connection and the outward heater hose I started the engine, there was no movement at tick over, if I reved to 3K there was some movement (small) and then tickover none. I repeat the pump vanes are perfect. So ignoring cracked block for second why no good water movement through the engine ?? I do not get it ! Anybody got any ideas ?
 
paulblake427 said:
OK, thanks for further info. However did fit water pump back on and only filled the engine with water by way as a test to see if there was water movement when the engine was running; there wasn't. I.E I disconnected the heater hose in the engine compartment point and left open and pointed it up, then removed the top hose completely, filled with water (I know there would be a small feed though from the thermo housing piping). However with the water visible from the engine top hose connection and the outward heater hose I started the engine, there was no movement at tick over, if I reved to 3K there was some movement (small) and then tickover none. I repeat the pump vanes are perfect. So ignoring cracked block for second why no good water movement through the engine ?? I do not get it ! Anybody got any ideas ?
Click to expand...
Collapsed Pipe, Delaminated pipe, blocakge in water ways etc etc etc

Blockage - maybe some donut has used Radweld or similar previously and it has finally found something to bung up, trouble is what it bunged up was a water gallery!!

Yer never know....

Now where did I leave that crystal ball.... :D
 
Stufer said:
Ok but don't jump to any conclusions... My cracked block manifested itself when warmed up only (as mentioned by James), but I did have over pressure and coolant loss from the expansion tank (you said you had no collant loss from here). The temp gauge would jump from middle to red very quickly and back again. Anyway it's been spot on since short block replacement. Good luck with it :)
Click to expand...
What was the cost of the short engine ? I guess there are no other routes to get orignial block repaired ?
Could you comment todays repy (mine) please.
 
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