Understanding 3FE Cooling System

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J

jeepmb

Joined
Feb 19, 2016
Threads
1
Messages
6
Location
Fort Collins, CO
Good Morning Gentlemen, I was referred here from the Pirate4x4 forums, hope someone has some insight here:

So, I've been working on a client's Land Cruiser for a little while now. The engine has received quite a bit of attention over the past year because it was neglected for a while. Its been overheating frequently, and dumping coolant after shutdown from what appeared to be the water pump. Also, multiple times after overheating it would release steam like a kettle from where the water pump meets the block. After doing some inspections, I found many of the smaller coolant hard lines completely plugged from corrosion. Thermostat tests fine in boiling water. Fan Clutch is fine. Water pump is new.

So my master plan to fix their overheating once and for all was to replace the now compromised water pump gaskets, replace thermostat gaskets, run a few strong coolant flushes (with cleaner), replace the plugged lines, replace radiator cap, replace WP bolts, and refill with proper distilled water/glycol mix.

BUT after a week doing all of this work the bastard car is once again dumping coolant after shutdown
pissed.gif
. If pressure is building up in the cooling system I can't understand why it is pushing its way out the water pump instead of the pressure cap on the radiator!

I need some brainstorming help here guys. Is there something about the way coolant circulates through this block that makes it prone to building pressure in the block? I cant for the life of me find a diagram highlighting how coolant circulates through this engine even looking through the FSM.
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Thank you for the diagram, that's exactly what I was looking for!

It is not an OEM radiator cap, which is actually something I am gonna try today. I just got one of the Saneki brand radiator caps (as opposed to our normally stocked Stant's) and noticed how the Saneki has more travel than the Stant that might be causing problems. I didn't think before that something as simple as a radiator cap would need to be OE, but...

Also, they did previously use radiator stop leak against my suggestions, but the appearance of the flush water and inspection suggests I got a lot of that stuff out. But considering how plugged the heater core is, its still possible I need a true pressure flush to get things appropriately clean. The thermostat can only go in one way, and it is an OEM design, so I don't believe that is the issue.
 
jonheld said:
If this motor has been overheating frequently, have you had the coolant tested for exhaust gasses? You might have lost the head gasket. The 3FE is pretty robust, but everything has its limits.
Click to expand...

Ya, we actually found the rear spark plug broken and rusted when doing the work, I believe that there may be a head gasket leak going on there, but I would still expect that the excess pressure should push out the radiator cap well before the water pump/block interface.
 
I would also expect a hose to burst before observing a leak at the water pump/block interface. Unless the mating surfaces were not properly cleaned before installing the water pump, or the bolts were not tight, I can't see this happening.
 
Both of those were my thinking too jonheld, but the radiator overflow passage is clear, and the mating surfaces were mirror by the time I was done with em. It does leak specifically from the top of the water pump, where those screws that hold the backing plate to the water pump lie. If this continues I might try to take a grinder to those screws (although they already sit very flush) and recess them a bit to make sure that they arent sticking out a bit when everything is torqued down.

Ill do more checks on the condition of the coolant, but glad to know that I am not crazy and that this cooling system should be working as I expect.
 
Another thing to try would be to manually pressurize the cooling system through the radiator with a pressure tester. The cap is rated at a low pressure (16psi or something in that area, I forget) and if the cooling system leaks at a lower pressure, then you know that the cap, hoses, etc are holding properly and the issue is the water pump.
 
To follow up, changing to the OEM radiator cap did not aleviate the problem. Still pukes at random after shutdown. Finally got a fan shroud on there, and head gasket symptoms arent resurfacing at the moment.

Next step will be following jonheld's suggestion to pressure test the system. Id hate to pull the water pump again, but its looking like thats the case.
 
Same issue here - coolant on ground only when engine is cold. '97 FZJ80. Has new radiator. Replacing all hoses, clamps, pump, t-stat, and gaskets with OEM parts. Even replacing nuts and bolts with OEM. Mine has a rebuilt head on it already - past owners had overheating problems with it. Runs and cools fine. Oils and coolant look good. We'll see - curious on what happened above.
 
Solved all my coolant leak issues with the OEM work completed. Took great care to have clean pump mating surfaces. Used no layer of sealant on gasket. Replaced radiator cap with OEM too - drawing coolant form reservoir tank now.
 
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