I recently changed my coolant expansion tank (new white one) and now the temp starts to climb when under load. Idling in the driveway, no problem, but once out on the highway, the temp climbs alarmingly.
What is the best way to burp the system, am I missing something? I have 176,000, and I'm sure it's the original radiator, so maybe I'm due for a radiator shop to work their magic.

Thanks for any help,

Mike

 

If overheating under load consider the following:

1. Coolant level (I filled mine when cold thru the removable plug in top of radiatior, threw the plastic plug away, and replaced wth brass 1/2 " NPT plumbing plug -$2 at hardware store). Then I filled the coolant jug and when coolant was running out of the radiator I screwed in the plug. Ran vehicle with cap off until warm, added coolant as needed. Some people say do this with front on ramps or up hill.

2. While that plug is open peer inside with flashlight and look for calcium build up on radiator tubes. Inspect space in front of condenser (AC radiator) and between condenser and radiator for trash - blocks airflow, usually noticed more at slow speeds. Check with light to see if fins are caked with mud, etc., wash out with hose or air pressure.

3. Thermostat - they are $10 - $20 cheap, and newer models have a small hole and "dingle" that allow air pockets to pass through. Be careful when installing that they don'r slip down and allow water to bypass the stat.

4. If overheat at road speed, the fan is not the problem, it provides little impact except when very slow or idle. Fan clutch for idle overheat can be checked - when cold it should spin only a fraction of a turn, when warmed to normal it should not spin a complete revolution, and when very hot it should be firm like when cold. At cold start it should "roar" with air flow, as viscous fluid spreads and de-couples slightly fan noise and air flow decrease. When cold mine pulls enough air to spin the AC fans even though AC is off. If fan free wheels, the clutch fluid is gone, change it, tech area has a $50 model for Chevy 2000 Express van, 4.3, w/o AC.

5. Water pump could be an issue. I did a recent post of internal photos of a bad and a good WP, side by side, so you can see what you will be getting into. I paid $7 at the salvage yard for one from an 01 low miles D2, they use the same pump.

6. If radiator is old (like yours), hunt for an indy radiator shop that works on all kinds, especially farm tractors and heavy equipment. A small place, one or two guys. They make their boat payments on the big radiators, not the little ones from pricey SUVs. A large shop will charge a lot, seems like they base it on the MSRP of the vehicle. Your radiator is brass and copper, and easy to remove (upper / lower hoses, two small hoses, and 2 oil cooler lines and 2 tranny cooler lines. They will "boil it" (flush an acid through it, usually heated, to convert calcium to mush and wash it out), and they will un-solder the metal tank, and use small rods to push in the radiator tubes to get the rest of the calcium, plus solder up any small leaks they find. I paid $65 for this. I had fooled around with white vinegar, commercial flush, and even a jug of brick washing acid (once radiator was out of the truck). The shop did a much better job. I did consider a salvage radiator, I just happened to pick one that had the oil cooler blocked, which is what killed the donor Disco. I would not get an older radiator from salvage unless you were planning on running it through the rad shop. Sometimes I have seen "new" radiators in the yards, they could be worth snagging.

If overheating at idle consider the above, plus the fan clutch, the fan blades on backward (cupped side goes toward engine), the AC fans wired backwards (blowing air out grille). Usually it it the clutch.

I learned not to trust the temp guage, it shows normal "1/3" reading for 135 - 210 degrees+ on mine. Any reading above 50% should be dealt with at once. A scanner that reads live data will give you a much better picture of what is going on. The scanner reads the data from the two wire temp sender, the guage reads the data from the single wire temp sensor right next to it.

 

Check the boiling point of your fluid with a simple cheap tool from the auto store. To burp or bleed, remove the radiator top plug. While the engine is running and warmed up squeeze the top radiator hose repeatedly to allow the air to escape while filling with more fluid. Wait for a few good overflows and Re-apply the cap while still squeezing the top hose.

 

How to bleed the system is in the tech section.

 

Also make sure you're doing all this with your heat on full blast to ensure you're rung your coant through the heater core tooincase that's where your bubble is. So when you have the plug open and are fiddling withthe top hose have the heat on full blast

 

If you don't burp it correctly, could the trapped air make it overheat after 2 months?

 

Not likely, air in the system should have showed up right away.
However if you have a leak you will get air back into the system.

 

Spike I looked through the tech section and couldn't find the thread on burping the system. I also searched and couldn't find the old thread I was looking for. I just can't remember which side we drive up on a ramp to bleed the system. Is it the passenger side?

 

Makes sense to have the passenger side elevated because the over flow tank is there and the radiator fill plug is there. The open portions of the system should be elevated above the rest of the system to allow more fluid less air.

 

Sorry, it is in the DII section.
The write up is how to bleed the cooling system on a DII, same concept on a DI.
https://landroverforums.com/forum/di...tem-dii-23072/
Fill radiator, leave fill plug off.
Fill coolant tank, leave cap off.
Start engine, turn heat to HOT both sides.
Let engine idle until thermostat is open and you have heat coming out of the heater.
Once air stops coming out of the radiator fill plug plug it.
Once the coolant level in the coolant tank stays constant replace cap.
Shut off engine.
Drive it for a day, let cool overnight, recheck coolant level, add if needed.