I have a DII 2000 with 128k miles on her. As you may recall, I have replaced the water pump, thermostat, fan clutch, coolant and water wetter, radiator. When on the road, the truck runs great. Temp is right in the middle. However, when I come to a stop, like at a light or when pulling in to my garage at work, about half of the time, the temp starts to climb to the top of the “White” area, never up to the “RED.”

I tried the Blue Devil which did stop the exterior head gasket leaks (although after draining and flushing the cooling system when I put the new radiator in, the leak seems to be developing again. The temp did not climb before I used the Blue Devil. Although, I didn’t drive the truck too many miles before that so I am not sure if it is something that developed after the Blue Devil or that I just noticed it after that process.

I am noticing that the spider hose the one that runs from the thermostat to the water pump, is swelling/bulging when the temp starts to climb. The thermostat is a standard, 195 degrees I believe. According to the RAVE, the coolant runs from the bottom of the radiator up through the thermostat and then out the hose to the water pump, as well as out to the top hose that had the bleeder screw in it, across the top of the radiator and then connects to the top of the radiator. The top hose is not swelling, only the one from the thermostat to the water pump.

Any thoughts? I don’t have an issue doing the head gaskets, I will need to have them done, I just don’t want to do them and then find out that it is something else in addition to the head gaskets. Thanks Phil

2000 DII 128k miles

 

This isn't Disco specific. But every single time I've opened an engine that had some miracle goo in it to stop head gasket leaks, it has looked like crap in the coolant passages. How else do you think this stuff works?

It gums EVERYTHING up. If your cooling system is marginal to begin with, this extra gunk is going to be enough insulation to see your coolant temps rise. By all accounts and experience, "marginal" is a pretty good description of a Disco cooling system.

I'm ready for the "but I've been running around for 4 years with that stuff in my truck and I've not had any problems!" posts. Of course it works sometimes. But once you do it and have cooling issues, I'd say its the first place to look.

If you're lucky, you can actually flush all of that goo out. Sure, you're external leaks will be back. If you don't have any internal ones that will prevent you from at least attempting to run the truck hard enough to figure out if the coolant temps are down, you've found your issue. Pretty much on the cheap. Not that the fix will be. But at least you'll know.

 

I know, I was so excited when the stuff sealed up the external leaks and it seemed to run great, then the temp climb issue developed. The odd thing is that the only hose that is swelliing is the one from the thermostat to the water pump, the diagrams show the coolant flowing from the thermostat to the waterpump, is that really the way that it runs? It seems odd that I would have swelling on an "in" line rather than on an "out" line. It did it before I changed the thermostat as well. Dang, many of you told me so. No I just want to know if I will just need a head gasket job or will I need an entirely new motor? I certainly won't resleeve this one. Phil

 

If you are heating up at idle, I'd check operation of your A/C condenser fan (considering all the repairs you listed), which typically comes on when the vehicle isn't moving/getting enough airflow. Overheating with head gasket problems typically occurs under load, not at idle.

 

https://landroverforums.com/forum/sh...ad.php?t=32216

 

Great ideas, thanks for the input. The A/C fans are working. One thought, when I put the Blue Devil in the instructions stated to make sure that the heater was on high. I never had a high temp issue until after the Blue Devil. I am wondering if the heater core has become clogged, with the Blue Devil stuff. As far as flushing the heater core, is there a recommended way of doing that? Can I just remove the input and output hoses and use a garden hose to back flush the heater core? Ideas? With a sleeve/block problem, is it typical for those to show themselves at idle or while the engine is under load? Thanks Phil

 

I was also thinking about a clogged heater core since the DII t-stat diverts coolant to the heater when at idle and not to the radiator.
Yes just remove the heater lines and back flush with the garden hose.

 

I took off the hoses to the heater core and did a back and front flush. Nothing major came out. I also took off the lines to the throttle body heater plate. They looked clear. I tried blowing through the plate housing and it seemed clogged. I took off the throttle body heater plate, 3 5mm bolts. The in-line was about 90% clogged with what looked like a calcium deposit. Cleared it out and put it back together. Bled the system and topped it off with distilled water. Started up and took it for a victory lap, temp gauge right at centerline. Took her for a quick drive around Pacific Beach and a stop at McDonald's for a 42 oz. Diet Dr. Pepper! Temp still at centerline. Back home and still at centerline. I can't believe that a clog of the throttle body heater plate and a quick flush of the heater core resolved the issue, but maybe I got lucky.....I will take her for a longer drive tomorrow and see what happens. This intermittent stuff drives me crazy. Thanks for the tips.

I am going to take a good look at the in-line thermostat. I still will need to do the head gaskets.

I did see a 2000 Discovery with a bad motor for sale today, $1000, I thought about it for about 2 seconds, and then thought that my wife would likely leave me.....3 Discoverys and one wife are enough for me. Phil

 

Man if you get this figured out that would help alot of others.

 

Drove around today for about 30 minutes, everything was great. Stopped at Costco for an hour and back on the road. Stopped to drop lunch to one of the kids, left the truck to idle, and sure enough, the darn thing started to get warm......I turned on the a/c and reved the rpms to 2000 and the temp dropped to normal. This thing has got me baffled. Phil