2000 Disco:

Water Pump: 1.5 yrs old
Hoses: all < 1 yr old
Thermostat: brand-new
Radiator: original
Heater core: mechanic purged using pressurized water.
I do not suspect a head gasket - no loss of compression, no smoke in exhaust, no milky oil, no visible signs of blown gasket.

Symptoms:

Sporadic overheating. Get's to red-line. When engine temp rises, there's no heat - it's stone-cold. When engine temp eventually lowers, heat in the truck is hot.

Observations:

No leaks - system is fully-pressurized when warm, coolant reservoir is consistently full.

Upper part of radiator is warm, lower is much-cooler.

My mechanic is dubious about the problem being the radiator. He's more inclined to suspect the water pump. I think that it's the radiator.

Thought's Rover gurus?

 

Sounds like the radiator is clogged up oh by the way if your temp gauge in truck hits red line your cooking your motor...... get a ultra gauge to monitor temps more accurately.

 

Thanks, I'll do that. I shut her right down as soon as I saw it creep up there..

 

The gauge won't show over heat until it is really cooking. A scanner or UG can show digital temps so you can see it creep up. If rad is blocked with sludge, lower rows are cooler, nothing going thru there. Got any sounds like water rushing in pipes under dash? If so, that is bubbles, and enough of it will knock down heat as well. Source of bubbles can be air (leak) or exhaust gas (head gasket or cracked block). But usually a blocked radiator is reliably overheating at certain load, etc. Sporadic is more questionable. A coolant chemical test for exhaust gas can prove/disprove that sort of issue, about $50 and can do many tests. Thermostat could be sludged up as well, from other work on system. Some non-oem thermostats have been reported to stick closed somewhat.

 

Thanks, guys. I appreciate your feedback.

I'm guessing that my next step will be to swap the radiator. I bought one about 1 year ago off of a guy who was parting out a Disco like mine. It has 80K miles on it, and I got it cheap. I'm sure that I'm taking a little bit of a risk with a used rad, but if worse comes to worse, I'll toss a new one in.

The thermostat is brand-new, as in < 20 miles on it. I don't believe that it's the source of my problem. My understanding of the coolant system is that that even if the t-stat went South, I would still have heat in the truck.

I think that our plan of action is to swap the rad, and properly bleed the system.

Agreed?

 

I agree that your taking a risk installing a used radiator.

 

One more observation before I drop $300 on a new radiator:

The top radiator hose gets warm when the engine is at running temp. If I run my hand over the radiator, starting right to left, the radiator is warm on the right, near the inlet, and it's stone cold by the time my hand is at the middle of the radiator.

How can I definitively diagnose if my rad is shot or if I have some other problem with my coolant system?

To refresh:

- overheats reliably - not sporadically sa I reported earlier
- no heat inside truck
- heater core was cleaned out under pressure
- found system still pressurized after 24+ hours of sitting - engine stone cold, when I opened the coolant reservoir, the system was still under pressure
- when at running temp, upper hoses warm, lower hose from t-stat to rad is stone cold
- new t-stat installed
- new hoses, with the exception of lower hose - t-stat to rad

Thanks again, guys!

 

You can use an IR thermometer to "shoot' the top and lower fins, more than 10F variance leads one to believe some sludge is in there. And guys post on here about new rads for well under $300. Rock Auto has a Nissens for $206 as an example.

 

Thanks! This may sound like an obvious question, but, given the symptoms that I described, if after pointing an IR therm at it, the rad points to sludged up, is this the most-likely culprit? What I'm hoping to avoid is tossing $200 at it, only to find that the "real" problem costs $1000 to fix. The latter scenario would might cause me to scrap the truck altogether, as it has 192K miles on it.

One more question: is it normal for the temperature to vary horizontally across the rad?

Yet one more question: does it make sense to try to flush the existing rad?

Off to buy an IR thermometer ...

Thanks for your help!

 

You can find a radiator for around $130 on eBay


A flush may break up some deposits or may not some have good results some waist money.

Temp should not vary much when it does there is blockage