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Weird overheating issue

3K views 9 replies 5 participants last post by  Cudadrt 
#1 ·
So I bought a 2001 Disco 2 a few months ago with 92,000 miles. Friend I bought it from had the head gaskets replaced. I've since put almost 7,000 miles on it with no issues. Now recently it overheated and I immediately shut it down and had it towed home. No smoke out the exhaust but building up pressure in the cooling system. Decided to change the water pump, thermostat, fan clutch, and radiator. Connected scan tool and monitor temp holding steady at 183-185. Drive it settings with thr scan tool connected tuo monitor temp for over an hour and then temp starts rising. Take it home and decide to pull heads and expect a leaking hg again. Once disassembled, no sign of a blown hg. No steam cleaned cylinders, but instead normal carbon build up. Inspected sleeves and none have moved. No coolant mixed in the oil. Installed new hg with arp studs. Decided to replace the thermostat and water pump again just to be sure they are good and replaced the coolant overflow cap. After putting back together, now temp is holding steady at 194, but still building pressure in the coolant system and pushing coolant out the overflow. Once it pushes out enough, of course, temp begins to rise due to lack of coolant. Temp will rise to about 203-206 and then go back tuo 194-196 when moving again. My plan next is to remove heads and have checked. Anyone else had and issues like this before? I've looked and looked and can't find any similar instances. Just seems odd that it was fine fot almost 7k miles and now overheating issues without any of the common symptoms of blown hg or slipped sleeve. Could the head be cracked?
 
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#2 ·
Sadly, your problem is probably the block. I would get an exhaust gas coolant tester to be sure, but it sure sounds like combustion is pushing through a crack between a cylinder and coolant path in the block. The cylinder walls are known to crack behind the sleeves, it wouldn’t be a shock to find one. But you have to pull the sleeves out to know for sure. If the head gaskets have been done, then chances are the engine severely overheated at some point. This could have been the original cause, or a product of the overheating.
 
#3 ·
I agree with Lkstk, The block probably has a crack, most likely between the 2nd and 3rd cylinder on either side. Have you developed any oil leaks? if its between the liner and the block you cant tell by water in the oil. Sometimes you can detect the moisture in the top of the oil fill cap. other times though it pressurizes the crank case and make seals leak that wouldn't normally, Rear main. The engine isnt getting hot because it is losing coolant as much as it is because it is losing pressure over the coolant witch keeps it from controlling the temp. The blocks also tend to crack near the head bolt location. The one next to the water jacket near the cylinders in the center. Have the gases checked, and don't let anyone tell you they can fix that for you. RPI Engineering, Famous Rover engine builders;
have a great video on just this subject on youtube. some place
 
#4 ·
Thanks for the replies. I do wan't to note that I did a coolant pressure leak test and it held 15 psi fine with no drop a couple days ago. I also started the rover and let it idle flor 45 minutes with the 15 psi on the coolant system and it did not overheat at all. I've ordered a new reservoir and cap to try first. I just think if the block was cracked, it would've leaked down under pressure or built up more pressure when running. I'm going to try the cap and reservoir first and see if that helps. I found coolant coming from around the top of the cap as well as slow drip ot the overflow tube. If those don't make any difference, I'll pull the heads and do a block pressure test. I did do the block test through thre coolant with the blue liquid and it did not change color, but I wasn't impressed with the tester I bought at autozone. I would like to try it again with a different tester. Thanks again for your input.
 
#5 ·
When you say it did not overheat - did you check the temp with a third party gauge? The infamous LR gauge in the dash is designed to move in one fell action when the temp overheats; it does not ratchet up slowly as the temp increases. By the time it moves to red the engine is often done. That is what causes all of us to replace the head gaskets.

Be sure to get a third party temp gauge. Most of us use one which plugs into the OBDII socket.
 
#7 ·
Yes I used my obd2 scanner. Temp started between 201 and 203 at idle. When I gave it a little throttle, the temp would come doesn't to 194 and then back up tuo 201-203 at idle. Thanks for the warning about the gauge as my research on it shows it reads in the center from 160 - 240. I've been using my scanner as my temp gauge through all of this........
 
#10 ·
So just to update anyone still following and those who use search and find this post, I changed the reservoir and cap today and so far so good. Temps are steady at 194/195 while driving and 201/203 when parked and/or idling. Drove around about an hour today and no leaks from the cap and normal change in temperature reading. I'll post back in a couple days as I really want to get more drive time on it and see how it does in the long run. I'll continue driving it and report back once more at the end of the week. Thanks to all who commented.
 
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