Cooling system leak - 3psi in 2 hrs? - Defender Source
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  #1  
Old May 6th, 2013, 07:02 PM
sro
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Cooling system leak - 3psi in 2 hrs?

I'm trying to diagnose an overheating issue that's been plaguing me since I purchased the vehicle. Truck can't really do a mountain pass without overheating. Offroading is also an exercise in patience.

Right now when the vehicle gets warm there seems to be very little pressure buildup in the radiator hoses. Maybe a couple PSI.

I also noticed there's a small cooling system leak. I pressurized it to 16psi and the system dropped to 13 psi over 2 hours. Could that leak be the cause of the overheating issue?

Water pump and fan seem fine. Did the jiggle test (on the water pump) and the newspaper test on the fan. Next step is to replace the thermostat.
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  #2  
Old May 6th, 2013, 09:19 PM
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16 to 13 or 16 to 3?

16 to 13 wouldn't be a problem.

On mine I pushed it a bit higher and had an old hose pop ... which probably had a slight leak.

Do you lose water ever?

Have you got a good seal on the expansion cap?

If you don't get good pressure in the system then it won't cool properly.

I battled this crap for years and eventually just swapped the head gaskets and now it's perfect. Even a tiny leak on the gasket wall will inject massive amount of heat into the water which is too much for the system to cool.
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Old May 7th, 2013, 12:25 AM
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I haven't noticed any coolant loss. I did a combustion leak test and it didn't turn up anything. Man a leaking head gasket would suck...

Does anyone know what pressure the vehicle should operate at after it's warmed up? I can squeeze both the top and bottom radiator hoses until they touch, which judging by an earlier thread means there's not enough operating pressure...
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  #4  
Old May 7th, 2013, 01:17 AM
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During my build the engine out of my old truck overheated very quickly. We opted to replace it with an identical unit with only 70k.
It was a pretty cheap alternative to pulling the old unit apart and finding more than you wanted to fix.
Because yours is so slow wondering if your block is showing signed of porosity. The overheat when pushed is the same symptoms as a buddy had before a new engine was needed.
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Old May 7th, 2013, 01:23 AM
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Well, just tested the radiator cap using my compressor. Cap is good. Another sign pointing to a leaky engine...

Would there be any other possible causes for the low pressure? I want to make sure I check everything before I start down the head gasket route...
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  #6  
Old May 7th, 2013, 06:49 AM
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Have you tried to put in the dye. It is a bit nasty to do but if you have an external leak it will show.
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Old May 7th, 2013, 02:29 PM
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Okay, I just went to the local auto store and picked up some dye. I'll let you know if I see any leaks over the next 24 hrs.

I have a friend that offered to do a compression test & leakdown test so I'll try to get those done as well.

Is there anything else that I'm missing?
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Old May 7th, 2013, 02:35 PM
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Quote:
Originally Posted by sro View Post
Okay, I just went to the local auto store and picked up some dye. I'll let you know if I see any leaks over the next 24 hrs.

I have a friend that offered to do a compression test & leakdown test so I'll try to get those done as well.

Is there anything else that I'm missing?
head gasket kit ... ;-)
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  #9  
Old May 7th, 2013, 04:19 PM
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Radiator plugged, thermostat not working properly. Dont jump to conclusions and think you need head gaskets. If it needed headgaskets that badly it would be massively pressurizing the cooling system and overflowing from the expansion tank like mad.

From 16psi to 13psi over several hours does not sound abnormal. It is likely a product of a change in ambient temperature or engine temperature if it was not absolutely stone cold when you did the test.
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  #10  
Old May 7th, 2013, 04:30 PM
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Other than the dye, you could also use a soap solution in a spray bottle and soak all the cooling system connections watching for leaks as evident by blowing bubbles (tire air leak method).
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  #11  
Old May 7th, 2013, 04:41 PM
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It doesn't sound like head gaskets--that is usually high pressure as it is combustion leaking into cooling system. I also doubt a porous block without seeing signs of depleted coolant. If your hoses are not pressurized, I would lean towards stuck thermo or blocked radiator or even a worn water pump. Usually the water pump leaks out of the hole right below the pulley--it is intentionally designed to do that when the bearings wear out, although if the pump is a cheaper sort with the plastic blades, it could wear out prematurely.
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Old May 7th, 2013, 09:19 PM
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I don't know what Land Rovers you guys are working on, but the majority of leaking head gaskets I see are leaking externally.

To the OP: What is the engine? Also, is the coolant leaking out causing it to overheat, or is it overheating without leaking out?
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Old May 7th, 2013, 10:41 PM
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3.9l

Testing for exhaust in the coolant came up negative.

Vehicle overheats without any visible coolant loss. Pressure in hoses is low even when overheating.
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Old May 7th, 2013, 11:06 PM
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Okay I'm going to try to replace the thermostat tonight. If its a radiator bloc shouldn't the input hose have a different pressure than the output?

What's a good way to diagnose the health of the water pump and radiator? I don't have an ir temp reader. The water pump is not leaking and the pulley seems firm.
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Old May 7th, 2013, 11:11 PM
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Quote:
Originally Posted by sro View Post
3.9l

Testing for exhaust in the coolant came up negative.

Vehicle overheats without any visible coolant loss. Pressure in hoses is low even when overheating.
Mine passed the coolant exhaust gas test.

If your system doesn't pressurize then you won't get proper cooling efficiency. I would look at the expansion tank and the seal from the expansion bottle cap. Maybe the expansion bottle has a hole or split?

Is the radiator blocked? Is it hot at the top and bottom?

Years ago my sister had a golf that would over heat and the mechanic couldnt find anything wrong .... Eventually he removed the new radiator and flushed it .... Out came a big chuck of excess plastic molding ...
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Soapy water / KY jelly, etc. is is basically a must. Yes, good idea to remove trim panels - only takes 5 more minutes to do so.
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  #16  
Old May 7th, 2013, 11:24 PM
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Sam Odio
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Took the expansion tank off and pressurized it to 15psi with my compressor. No problems with the tank or cap.

Both top and bottom rad hoses are hot and unpressurized. It's possible that the bottom hose has some very week pressure but its hard to tell.

Under most driving conditions the truck seems to stay around 180deg. Only on hill climbs or during offroading does it get hot.
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  #17  
Old May 7th, 2013, 11:28 PM
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I would guess a plugged rad or bad water pump.
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Old May 8th, 2013, 07:52 AM
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yep i'm leaning towards Ron's diagnosis
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Soapy water / KY jelly, etc. is is basically a must. Yes, good idea to remove trim panels - only takes 5 more minutes to do so.
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  #19  
Old May 8th, 2013, 09:29 AM
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Radiator or fan clutch would be my guess.
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  #20  
Old May 8th, 2013, 10:21 AM
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Quote:
Originally Posted by Jymmiejamz View Post
Radiator or fan clutch would be my guess.
fan clutch wouldn't cause system to failure to pressurize
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Soapy water / KY jelly, etc. is is basically a must. Yes, good idea to remove trim panels - only takes 5 more minutes to do so.
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