Coolant leak, unsure of location (1 Viewer)

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So, I've done plenty of work on my '93 FZJ80, including but not limited to rebuilding the head/HG, replacing the PHH, rebuilding the front axle x2, rebuilding the rear axle, and plenty of other things. Earlier this year I went to help shovel snow at my church, and on my way home my cruiser overheated and shut itself off. There was no hint of coolant burning in the exhaust, but it had blown out pretty much every drop of coolant, but I could not see where it all went. I towed it the remaining .5 miles home, and finally started working on it last week (working from home, don't have to drive it). I replaced the thermostat and water pump, and then started to fill it up with more coolant. As I got to about 3/4 gallon in the system (filled through the radiator), there was a leak but I still couldn't see exactly where. I replaced the radiator when I did the HG, and I can see it's still in really good condition. I can see all of the front and rear of the radiator and the leak either isn't coming from the engine radiator, or it's coming from somewhere I can't see.

My suspicion is that the thinner, black radiator just in front of the main radiator has a leak, but I can't see into there. I have the FSM, but for the life of me I can't figure out whether that is the transmission cooler or something else, so I am not sure what I'm going to need to do to gain access and see where the leak is.

As far as I can tell, the leak is down low, not coming from any hoses or fittings, and is on the driver-side. Any thoughts on where it could be coming from or what I'm going to have to do to see it directly?
 
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Mine leaked through the rear heater core line. And I also have a small crack on the block at the freeze plug next to the oil filter. Maybe check those locations as well.

In front of the radiator is the ac condenser and then the smaller cooler is the transmission oil cooler.
 

ppc

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I replaced the radiator when I did the HG, and I can see it's still in really good condition. I can see all of the front and rear of the radiator and the leak either isn't coming from the engine radiator, or it's coming from somewhere I can't see.

I seriously doubt you can see "all of the front and rear of the radiator". If the fan shroud is in place much of the engine side is obscured including the top and bottom tanks. Your description is vague but a leak of any sizeable amount should be easily identifiable. Don't ignore anything because it is new or recently replaced. Have you located the radiator petcock and made sure that is tight? If you're unsure of the location keep adding water and crawl under the vehicle and look. If need be, rent a pressure tester from you local auto parts to attempt to pressurize the system. Was the replacement radiator OEM or some other brand and did you do the repair or have someone else do it?
 

SNLC

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My suspicion is that the thinner, black radiator just in front of the main radiator has a leak, but I can't see into there. I have the FSM, but for the life of me I can't figure out whether that is the transmission cooler or something else, so I am not sure what I'm going to need to do to gain access and see where the leak is.

As far as I can tell, the leak is down low, not coming from any hoses or fittings, and is on the driver-side. Any thoughts on where it could be coming from or what I'm going to have to do to see it directly?

You don’t have a “thinner black radiator in front of the main radiator”. You have a A/C condenser and a trans cooler. Neither hold coolant.

Check your lower hose on the RHS from rad to thermo housing. Check your drain cock in the rad. Check around the oil cooler. PHH or heater hoses will be in the back and run down the block, head and bellhousing.

How long did it run hot before it shut down? What do you mean by all the coolant was gone? You burned all your coolant before you shut it down?

Even if it only ran hot for one minute I suggest you do a coolant test to check for combustion gasses. You got a cast iron block with an aluminum head and an awful stock temp gauge. That is just not a good combo for head gaskets. The key to HG longevity is not let it ever get hot.

Cheers
 
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Further to what has been said, at least the 1HD-T engine has plugs in the block. These plugs corrode over time and leak, and some of them are not obvious at first sight. If your engine has them, try to make an inspection.

Good luck!
 
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You don’t have a “thinner black radiator in front of the main radiator”. You have a A/C condenser and a trans cooler. Neither hold coolant.

Check your lower hose on the RHS from rad to thermo housing. Check your drain cock in the rad. Check around the oil cooler. PHH or heater hoses will be in the back and run down the block, head and bellhousing.

How long did it run hot before it shut down? What do you mean by all the coolant was gone? You burned all your coolant before you shut it down?

Even if it only ran hot for one minute I suggest you do a coolant test to check for combustion gasses. You got a cast iron block with an aluminum head and an awful stock temp gauge. That is just not a good combo for head gaskets. The key to HG longevity is not let it ever get hot.

Cheers
I can't remember how long it ran after the temp light came on but before the engine shut itself off. I'm definitely worried that I'm looking at another HG replacement, so I'll keep working through troubleshooting incrementally. Thanks for the advice!
 
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Further to what has been said, at least the 1HD-T engine has plugs in the block. These plugs corrode over time and leak, and some of them are not obvious at first sight. If your engine has them, try to make an inspection.

Good luck!
It's definitely not coming from the engine itself, but I'll keep this in mind!
 
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I'll probably pull the plugs first and go from there. I did only recently replace them to prepare to pass CO emissions testing, but they should show some clear indication of HG failure. Thanks @BILT4ME!
 
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I seriously doubt you can see "all of the front and rear of the radiator". If the fan shroud is in place much of the engine side is obscured including the top and bottom tanks. Your description is vague but a leak of any sizeable amount should be easily identifiable. Don't ignore anything because it is new or recently replaced. Have you located the radiator petcock and made sure that is tight? If you're unsure of the location keep adding water and crawl under the vehicle and look. If need be, rent a pressure tester from you local auto parts to attempt to pressurize the system. Was the replacement radiator OEM or some other brand and did you do the repair or have someone else do it?
Good points! I need to remove some more things to have full visibility. I can see the majority of the fins on each side of the radiator, but not the remainder of the edges. Replacement radiator is not a true OEM part, no. I'll need to check again for the petcock and continue troubleshooting. Thanks for the help!
 
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Please check your FHH. The small hose just in front of the PHH. Coolant can steam out of the hose and leave you without.
It may not be apparent with a visual, so look carefully.

FHH is under the intake manifold on the block about 6" away from the larger PHH. Search for it- common
 

saraujo

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Not yet, I need to get my phone ready before I put more coolant in, then mark it up before posting so it's easier to see.
I think it may be (correct me if I'm wrong) the rear heater lines? I replaced these 'field goal' sort of pipes which had a leak on the metal pipe side where the hose connected to them. Sorry, that's the best description I have for them. Since my rear main seal was already leaking, it was easier to replace them with the transmission out of the way.
The photos of this gents rear heater lines in this link here: Rear Heater Delete/Coolant Line Cleanup - https://forum.ih8mud.com/threads/rear-heater-delete-coolant-line-cleanup.1088550/page-5#post-13188037 - reminds me of what they looked like. The attached picture shows where you can see the newer 'black' part of that pipe near the heater valve, which leads me to believe these are the heater lines, but I could be wrong. What lead me to believe this in this case, is because I also could not see where the leak was coming from when it happened to me. After replacing it, no more leaks. And trust me, it was frustrating because to this point, I'd replaced every single coolant hose on my truck.

I hope this helps.

IMG_7399.JPG
 

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