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Discussion Starter #1
Hi guys, I am new to the forum because I just bought an 03 Disco for my wife. I bought it knowing it was overheating and basically suspected a head gasket because the PO replaced the water pump, thermostat and radiator as well as many hoses. I assumed he replaced them and it still overheated so he gave up on it.

So I bought a head gasket set and the throttle pre heater because that was leaking and replaced both. The old head gaskets looked ok and showed only minor signs that combustion could have been leaking into the coolant passage. Heads were flat and block looked good. Also there were no signs of coolant leaking into the combustion chamber, all pistons were black with carbon.

I can let it idle in my driveway for 5 minutes or so and it will hang right in the middle of the gauge. Once I go drive it down the street it will stay there for 30 seconds or so then quickly rise and overheat, like within 5 seconds of moving off half mark it is in the red and coolant is purging out the surge tank.

It does it every time. I dont understand whats going on. I even put another new thermostat on it but it still overheats almost randomly when you drive it. When I had it apart I inspected everything carefully, all coolant passages were clean and unblocked, even took off the new water pump which was good, fan clutch is strong, there are no leaks now. At first I thought I hadn't bled the system well enough but I redid everything and bled it from the upper hose connections.

Should I suspect a cracked head? Something wrong with the block? I didn't take the heads to the machine shop but I have a straight edge and the surfaces were good, even still the coolant passages are only on the two edges of the heads. Am I missing something?

I am a GM certified master tech, ASE master tech and I have extensive Kia/Hyundai training. I don' think Ive ever been stumped by a cooling system before. I bought the 03 because I read of improved head bolt design causing less gasket failures and cylinder liners that were improved. I really really don't want to buy a new engine or head.
 

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Don't rely on the temp gauge on the dash. It reads in the middle for a wide range of temps. I don't recall but its around 180-240. Get an obd II reader or a scan gauge. This will give you a better insight to what's going on.

If you have an Android device you can download a program called Torque and get a Bluetooth obd II reader for $20.

Is the electric fan (in front of the radiator) coming on.
 

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How bad and many time has the engine overheated? There is a good chance you have a dropped sleeve, do you hearing engine ticking once it warms up?
If you want some help, PM me your number and I'll call you.
 

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Discussion Starter #4
I have a Snap On Solus Ultra that I watch the temp with, the gauge being in the middle simply tells me its not overheating.

A couple things since I posted this. I checked the temp of the air coming off the fan, its plenty hot telling me the thermostat is circulating coolant through the radiator. The biggest thing to note is that I turned the heater on and don't have heat, unless the digital climate control won't let it come on because it was 95 degrees out.

I bled the system so many times I can't imagine there being any air in the system though it is possible. At this point Im thinking I might just have to suck it up and get an engine or at least cylinder heads.
 

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disco biscuit
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It really sounds like there's still air in it. My heater wasn't working while having a few air bubble problems. I would tell you the correct way but I don't have a solid answer for ya. I drove mine home, let it cool off and filled till it came out the bleeder while holding the coolant tank up. I think what really did it was leaving the cap off and filling it once circulating. They say to let it sit overnight.
 

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You might want to take me up on my offer.
 

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Discussion Starter #7
I will Mike thanks my phone battery died but I will call you tomorrow.

I am not ruling out that there may still be an air bubble, I bled it every which way I could think of but I have had stubborn air pockets before (in other cars). Tomorrow hopefully after talking with Mike if we don't get anywhere Im going to pressure test the system and see if I have any leaks, if not and the pressure leaks down I'm probably looking at a head.
 

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disco biscuit
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Yeah call mike. A pressure test leak down kinda just proves the coolant systems leaking somewhere. A chemical block test can detect hydrocarbons present in the system...sometimes a better test...doesn't really rule it out still. You should call mike and be sure to come back and type out what works for ya. Like I said I really don't know the best way to chase out the air. Being you just changed the H.G.s, I would look at it for a week unless I find concrete head evidence. Hydrocarbons would be one..mikes real busy with this and other disco forum dealings so it helps him for you to write it.
 

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Discussion Starter #9
Talked to Mike today, basically Im going to get a coolant pressure tester and see if it holds pressure. If not Im going to do an old trick that someone taught me and that is to remove all spark plugs and put my automotive stethoscope on with just the tube on the end and stick it in each hole until I hear air in one of the cylinders.

I also have a boroscope, if I am able to pinpoint which cylinder is leaking I may get lucky and actually be able to see coolant dripping in and where its coming from.

If its not leaking for some reason, well then I am back to square one. I will keep you all posted.

-Joe
 

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Then we talk again before you resort to a bore shop that won't show you anything and a stethoscope that also won't help in trouble shooting a Disco over heat issue.
 

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Discussion Starter #11
I pressure tested it today and you're right, a boroscope and stethoscope won't help me....when the system holds pressure. I pumped it up to 18 PSI, it bled off about a pound in the first minute then it held losing less than a pound in the next 5 minutes. Tried it again and it did the same thing.

So next I started it up again and ran it at idle for a while, just making little checks here and there. Once it was warmed up I drove it around the block again, once I pulled into my driveway it was already starting to overheat again. I pulled out my infrared thermometer and noticed the face of the radiator was rather cool, like 100-120 while the upper hose was 175 and the lower hose was 120. On the other side of the thermostat the return hose was 120-130 and the upper hose was 170 or so.

It almost seems to me I have a flow problem. At my next chance I will take off all the hoses and flush the system through just to make sure there is no blockage anywhere. If not I will go back to the drawing board bleeding the system.

-Joe
 

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Joe, flushing won't help it. I would do a chemical blow test to rule out exhaust leaking into the coolant system. If that doesn't show anything, then it is time to start pulling her down.
 

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Only way to properly bleed the coolant system is to do it when the engine is cold, not running and the bleed completely removed.
Fill the coolant bottle till you get a steady stream of coolant from the bleed screw, replace the screw and cap, start the engine with both heaters full hot fo a couple of minutes. Then the next morning before a cold, check and add coolant till the level is about 1/2" above the seam of the coolant bottle. Usually I suggest you check it a couple more times over the next week, only when it is stone cold and you should be fine.
 

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disco biscuit
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I really believe that may be it. Mine had exactly the same symptoms including cold coolant to the touch and infrared. It seemed like mine lost prime or something from the air. Then seemed the gauge was reading steam pressure but for lack of water against the thermostat it wouldn't open. I let it run even though the gauge..I had a damn infrared on it, and eventually it just opened, pulled water through the open water reserve I topped it off and it worked. Mine also never exceeded 3/4 of the gauge range. It wasn't actually on hot.

"Not the right way to do it" disco biscuit
 

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Discussion Starter #16
Worked on it again tonight (I only get like an hour or so after work to actually look at it). I put the pressure tester on it again and this time instead of pumping it up I started the car and watched the pressure rise on its own, and rather quickly like 10 PSI in the first 30 seconds. Hoping I could get it to show some signs of leak down I monitored pressure and held it at 20 PSI while the car warmed up then shut it off. I was hoping maybe once the aluminum heated up it would start to bleed pressure off and I could finally rule it a combustion-in-the-coolant issue but alas, it held strong for 20 minutes.

Tired of messing with it, I am going to get a chemical block tester tomorrow and check it tomorrow night hopefully.

Will keep you posted.

-Joe
 

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disco biscuit
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I have to mention to you. You said you put an infrared on it and the top hose was 170 and the bottom was 120 max. Have you verified any water might be over 200. Your thermo don't open till 180 at least. Stock is closer to 200 to open have you verified the thermo even opened. I'm practically screaming at you my 04 registered hot before the thermo opened and circulated when, in fact it was no where near over heating. When you say that and you have an hour a day to look at it. Have you circulated with the heat on and verifying its actually getting hot vs the gauge. I still question it for some reason.
 

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Discussion Starter #18
Yes I verified it. Remember I was measuring the outside of the hoses not the actual coolant temp.

Either way, I bought a chemical block test kit today and tested it, sure enough it is leaking combustion. Tomorrow I will be pulling the heads and will send them to the machine shop Wednesday, just what I want to do on my two days off.

Again, Ill keep you all updated when I find out what the machine shop says.

-Joe
 

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I know a guy that had an 01 that had the heads done and went through the exact same thing you have been decribing. His issue ended up being that he had purchased a stud kit but had torqued them to the head bolt specs. The over torquing actually pulled the threads up and out of the block about 1/16 of an inch in a couple areas.
 

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disco biscuit
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Right on. You did good. Sorry for the results. 40-50 for a hydrocarbon test at Napa sux but there it is. If it shows positive its for sure negative can still be a head. Did a machinist check the heads before the gasket job. I might not of got hung up on the air bubble if the answer is no. It could also still be a slipped liner throwing carbon.

Also the possibility mentioned above. I think if installing studs, the target torque should be observed vs the described 30 or so lbs then 45° then 90° or whatever for stretch bolts. Also target toque is never achieved in industrial situations unless the described lubricant if any is applied. Meaning under torque if not lubed over tq if not required.
 
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