Ok, so I came across a good deal on a 2002 disco ii SE at a nearby mechanic. He said it had blew the head gaskets and that he replaced them, put in new radiator, water pump, thermostat, temp sensor, full tune up, and belt. But he said, about after an hour of driving it would start to overheat. So I bought the disco on a chance, also me being a mechanic/owning a lot of cars. I have been doing some research and I know About the blown head gaskets, liners cracking/slipping, the burping of the coolant system, temp sensors going bad, fan clutches going bad, etc. so I check everything,(looks to have a new radiator, waterpump, thermo, etc) burped the cooling system, checked the engine fan for resistance, bought a UltraGauge, and drove it around for about an 40 minutes. No slushing/gurgling sound, no visible leaks/ steam, no white smoke, no water in the oil, runs/starts like a champ, and most of all.....no loss of coolant! It runs about 184-192F around town and the heat works great, but soon after, when I started to go up a hill about a mile long, towards the top it got up to 206F before I backed off for fear of overheating, even though the normal temp gauge was still at half way....as usual...knowing that when it starts to show it going past the middle on the factory gauge, it is too late and is overheating....lol.... Please note that I am at 9000 feet roughly above sea level, so the boiling temp lowers to about 195? I'm not sure of the "danger zone" levels of the cooling system..... So I hopped out and checked to see if the top hoses had too much pressure, indicating another bhg or cracked liner/ block. The hoses were warm yet they were as soft as when they were cold, no change. No steam leaking out of the coolant cap, which looked semi new, but when I squeezed the hose, the coolant level in the reservoir, went up with ease. Also, soon after that drive, I cracked the cap open and a little poof pressure came out but not much at all.....


List possible things

1. The cooling system is not building up pressure, causing the water boil?
Coolant cap, resivour, water pump, mystery leak
2. Thermostat is acting up? Possible change to warmer weather thermo from Atlantic British?
3. Possible more burping?
4. Maybe I'm overreacting? LoL


I know this is common, and i've done a pretty good bit of searching, so Any info will help

Update

So I ruled out the viscous fan, electric fan is correct, replaced thermo with 180 soft spring and found my old thermo to be gutted. Now with the new thermo, I am overheating at idle from a cold start, with hood open in about 10 minutes. Took some measurements with my infrared thermometer.

Opened hood, checked coolant(good level and none was lost), no water in oil, no slime under cap, etc. Rebled the cooling system after sitting, stone cold, it being 31F degrees today and sitting all night in around 27F degrees, on a hill with elevated overflow reservoir. So here are my infrared temp readings with the car idling from cold start, for about 7 minutes to the temp of 212F kicking the fan on, according to the ultra gauge monitoring the ecu. Measured everything in the car engine bay before starting, after starting and after turning it off. Note this by seeing some of the temp ranges.

-=Cold engine bay before start=-
Note* 88F ecu reading coolant temp at start, on the ultra gauge.

Coolant reservoir and coolant inside - 38-40 F
Coolant bled from upper hose - 39F
Hoses upper - 36-38F
Hose/ thermostat lower - 34-37F
Metal heater core hoses -35-36F
Metal pipe from intake to upper hoses 36-37F
Temp sensor outside temp and aluminum manifold it goes into - 37-40F
Rad temp in various areas - 34-36F
Water pump - 35-36F
Upper intake manifold - 34-35F
Exhaust manifold - 30-32F
Random spots on the head - 36-39F


-=engine warm to 212F while running and turned off=-
Note* 210-212F according to ultra gauge and fan kicking on

Coolant reservoir and coolant inside - 74-78
Coolant bled from upper hose - 150-153
Hoses upper - 124-132
Hose/thermostat lower - 87-94
Metal heater core hoses - 94-98
Metal pipe from intake to upper hoses 137-146
Temp sensor outside temp and aluminum manifold it goes into - 149-153F
Rad temp in various areas - 74-79F
Water pump - 115-120F
Upper intake manifold - 71-78F
Exhaust manifold - 390-420F
Random spots on the head - 130-160F




My question is, does the electric fan run off of the same sensor as the gauge?
Answer: Yes it does, the ecu Reads the temp, then controls the fan.

Could he have installed the wrong sensor, a faulty one, or reused the same one that might have broken?
Answer: The sensor was faulty, by a brand named FAE. Was reading almost 40 degrees higher than what it was. Replaced with a Lucas part. Fixed problem, no more overheating.

 

Increasing load will account for the extra heat... the ultra gauge is a digital representation of a mechanical process. Its good for what your truck normally runs at.
The electric fan kicks on at 212F, so that is a little ways from the danger zone.

Sounds like you are doing all the right things, and have the right knowledge.

217 to 200 is when I would pull over...

Pik

 

you coolant system is not open to the atmosphere so you altitude will not make a difference.
You should try replacing the resinior cap, I would also preasure test and H20 test the cooling system.
Just because he did all that work does not meen it was done right. for instance if you were repairing a truck to sell would you pay $300 on machine work or like most places just throw the head on and hope it makes it out to door?

 

Have you ever heard your electric fan come on, have you checked and replaced your viscus clutch and consider installing a new 1800 degree soft spring t/stat, BPoU is where I just bought mine from.

 

Perhaps replace thermostat with a new one, the 180F soft spring version. With all the work, there could be a build up of trash in the top leg of the stat, where small holes allow a metered quantity of hot coolant to mix with chilled coolant from the radiator and make the stat open. Change the size of the holes and you change the performance of the stat. Always check belt route.

The oem stat is supposed to start to open at 180F, and be fully open at 204F, but that would be measured at the stat, inside the block is a little higher (where sensor is mounted).

You are wise to watch temps with scanner. Check electric fan for operation (turns freely, not siezed, fuse good) and viscous fan (feels like peanut butter inside, does not freewheel when warmed up). No gurgles under dash (air or exhaust gas bubbles).

 

206 up a hill is fine
you need a soft spring 180 in there now and quicj

 

I figured under a load, it would build up heat, but I wanted to know my range before i went any further. The fuse is good and the electric fan spins fine. The viscous fan, is tight when cold and has pretty good resistance. I will turn off and check when warm. What temp does it supposed to kick on at?

If there is a hole in the system, it is open to the atmosphere! Actually, this car was being fixed and the mechanic dumped all this work into it, and couldn't get it fixed. He does pretty good work, but was stumped. I got this thing for 1200$.... Basically, the work and parts he dumped into it. I could part it out and scrap the rest, to make good money, either way...but it's worth more and better all together if it is fixable

I'll look into checking the thermostat out and possible replacing it with a cooler running one. The belt was triple checked and put back on by me. My question is, why is the system is not holding pressure? I don't have a pressure tester yet, but I do have a compression tester. Might as well check that, too.


I'll report back soon


Also, I have a check engine light on and I've been doing some research. A p1451 and 0477... Emissions I think? I'll do more research.

 

206 degrees is nothing you are over reacting. Coolant should not boil at 195 unless I'm missing something.

 

Better to react than to regret

 

Ok drove it some more today, and after about an hour of driving it got up to 210 and the fan kicked on. Felt the top hose and it was normal feeling. NOT super firm, but warm and firm. I ordered a soft spring thermo and expansion tank cap, either way just in case.

I'll still keep an eye on it and see what happens. Still no leaks.


Update soon.