Cooling System Question

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Feb 26, 2008
San Diego
I have been noticing some slight coolant loss after driving my stock setup '82 FJ40 (2F). I would have to top it off in the overflow bottle after every few trips (I was also checking the radiator to verify it was just the overflow bottle that was low). Now I know I was due for a new radiator, and was getting ready to source one since the local quotes to refurb were more than a new aftermarket 4-core. Then, I was coming home, pulling into the garage, and saw coolant flowing out underneath (just coolant, no oil, so hoping it isn't a head gasket failure). It wasn't coming from the radiator, nor from the hoses, but it appeared to be coming from the water pump. It pretty much drained itself of all the coolant in the system (well over a gallon of coolant collected underneath the rig). So, I figure this might be a good time to go through the entire cooling system and inspect/replace any parts that may need replaced now or later since I don't know when the PO last did this.

Here is what I am planning to inspect/replace. Would love to get everyone's thoughts on what I might be missing or not thinking about.
  • New radiator (4-core, probably radiatorbarn or CCOT)
  • New hoses
  • New waterpump w/ gasket
  • New thermostat w/ gaskets
  • New belts (might as well since I will already be in there)
  • Flush the system and new coolant
I also figure I will pull the valve cover and check the oil to make sure no coolant is mixed in (rule out head gasket failure). Also, the fan clutch seemed to be working prior to the water pump failing, but should I be concerned that it may have failed too?

Any thing else I may be missing? Thanks in advance for everyone's help.
that is a nice list ...

but, what about the lines that go to your space heater behind the seats?

What is a trip? 5 miles? 500 miles?

since you see water at the water pump, start there, although if it has been a while since those seals were changed, say 5 years or more, then servicing them now as a elimination sequence is not a bad deal. two for the price of one, ... assuming your leak is found.

i'd keep looking for the leak. you can rule out the oil and water mixing by looking at the dip stick, and checking there. or change the oil. that would do it too.

water pumps do go bad from time to time...nothing unusuall there.

and, if those belts are more than 5 years old, i'd replace em myself. assuming 50k miles or more since last belt changes.

oh ya, as long as your changing hoses, change the short hose just above the water pump. that is one that gets ignored more than changed, and it will save you time to do it along with the water pump.

have fun, :):clap:
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sounds like coolant is coming out of the weep hole in your water pump , its telling you the impeller seal is bad . a gallon is a lot to come out of a weep hole but i guess it could happen .

time for a new water pump .
X2 what he said. Buy a coolant system pressure tester and determine the exact cause instead of the shotgun approach.
Thanks for the input

Sounds good, thanks. I will replace what I know is bad (radiator, hoses, and water pump) and then pressure test it as recommended to see if there are any other weak spots. Thanks for the heads up on that small hose above the water pump, I'll make sure to do that at the same time.

I did check the dipstick and didn't see any water, but I figured I would change the oil after I put the cooling system back together to double check.

No space heater behind the seats, and the stock in-cab heater was replaced with a Vintage Air unit by the PO that hasn't worked since I got the truck (but that is another project for another day, but I have a feeling it is an electrical issue). A couple of the heater hoses in the engine compartment have seen better days, so I will replace those too.

Thanks again for the input. I'll go start ordering/sourcing some of this stuff.
Update.....and another question.....

Okay, so I finally found some time this weekend to work on the cooling system. Got everything back together, and it is now running hotter on the in-cab stock gauge than before. My guess is that it actually okay, but the new temp sender is causing the gauge to read differently than before. Before the new cooling system, the gauge would run consistently at about 60% up the dial. Now, after the new cooling system, I am running about 80% up the dial, just past the last hash mark before reaching the upper Hot mark. BTW, I am running a stock 2F.

Here is what I did:

New water pump (OEM) and gasket
New t-stat (OEM) and gaskets
New 4-core radiator (aftermarket CCOT)
New hoses, both radiator and heater hoses all around
New drive belts
New temp sender (aftermarket CCOT)
Flushed coolant (didn't have much ugliness come out when I drained, as it had been flushed fairly recently)
New coolant (50% / 50% mix)
Burped system (rad. cap off, front end jacked up, brought engine temp up, saw the bubbles escape)

Using same fan clutch (was working before, but haven't re-tested)
Using same fan with fan housing (stock, I believe, but not certain)

I did not pressure check the system.

I did check the oil dipstick to check for any water, but didn't see any (to rule out headgasket failure).

The gauge seems to settle just past that last hash mark prior to Hot and then stabilize, so I am not sure if the new temp CCOT sender isn't fully sync'ed with the stock gauge and is just registering at different ranges (if that makes sense). I did take an cooking thermometer and stuck it in the filler neck after the truck came up to operating temp and the in-cab temp gauge leveled off. The cooking thermometer read 170*F, so it leads me to believe all is well, but I am still a little unsure. I am planning to put the old temp sender back in this evening just out of curiousity to see if it comes back to the original baseline it was at before.

Any ideas/opinions?

It was the aftermarket sender....

Borrowed an OEM temp sender (big thanks to Calixto) to test out, and that seemed to resolve the issue. Its now running in the expected range on the gauge. Seems the new aftermarket temp sender from CCOT wasn't matching up with the stock in-cab gauge, so it was showing a different range on the dial.

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