How did you bleed it?

Did you bother to check the heater core for flow?

Do you have a laser temp gun? Something that will tell you the temp?

We dont want to hear what you think you may have did wrong, we want to know what you did.

What coolant and when was it last changed for new?

 

Well, let's see if I can answer in order.

I bled the system by removing the bleeder plug and raising the expansion tank with the cap off. Since replacing the thermostat, I've done that about... 4 times.

I haven't flushed the heater core, but both heater hoses are hot when up to temperature, which should indicate normal flow through the heater core. If I end up tearing the cooling system apart, I'll backflush the system just to be certain, but I feel pretty good that it's not that.

I do have a laser temp gun, and I haven't looked yet, but I'll take it out when it's not dark and pouring. I'm not sure where to point it though, so any advice there would be welcome.

The coolant is Zerex G-05, which is OEM spec for modern Rovers and a number of other European cars. I changed it out and flushed the system about 8 months ago, but just to be certain, I've gone ahead and bought a coolant tester to see if anything is out of the ordinary.

 

There are a couple methods of bleeding...the one that works for me, drive up onto a STEEP hill. Leave it run and squeeze as many hoses as you can. The intent here is to dislodge air. I dont raise my bottle. I just make sure to get the bleeder to the highest point while squeezing the hoses. I do open the bleeder multiple times while parked on the hill.

Laser thermometers, kind of cheap now, point it around your engine bay. See where the temps are majorly different.

Coolant, I use the old green stuff. All the "newer" types of coolants have a tendency to gel up and clog parts when in contact with air or other substances. Not saying saying you made a bad choice, I just dont prefer anything except green.

 

Thank you for the advice. I come bearing additional information of questionable usefulness!

Bled the system again. I think I got some more air out; my next plan is to put the front wheels up on the curb and try again.

Turned the car on and the heater at max. Temperature eventually stabilized at 194. Readings from the laser thermometer were 160 at the top hose (skeptical), 144 at the hose from the thermostat to the pump, 183 from the heater hoses, with excellent heat.. Temperature would not go above 194.

Closed the hood to go for a test drive, which is where everything started to go south. As soon as I started driving, temps went up into the 200s. I ended up having to turn the heat down for my own sake, which is when it hit 212 and stabilized, presumably when the electric fans turned on. Pulled back into my house and temperatures stayed at 212. Turned the heat back to max and the temperature dropped to 203 and stayed there. Radiator top hose was 173, thermostat to pump temperature was 145, heater hoses were at 180. Revving the engine dropped the temperature into the 190s.

I've got a couple things going on here. Obviously, I need to go in and make sure there are no more air pockets. I've also ordered a Hayden fan clutch and a refractometer. There's a possibility that the antifreeze concentration is too high, although I don't really trust the cheapo hydrometer I bought as a sanity check. After that, it's going to be water pump and radiator replacement as a last resort.

Thanks for all the help!

 

Update, 1/6: I've bled the system (again), and installed the severe duty fan clutch. Temperatures are around 199 on the highway, and 206 at idle in 50 degree weather, which I'm still not entirely happy with. When I took off the fan shroud, it revealed that the radiator was replaced at some point with a Nissen, so I'm hoping it's in good shape, but I'm not sure. Is this a typical operating temperature for these sorts of conditions?

There's still no waterfall noise, but when you turn the car off, there is a (very) faint bubbling noise behind the dash, so I'm assuming there's still a small amount of air in the heater core. Apparently the hill I parked on when I bled it the last time wasn't steep enough, so I'll be doing that again anyway.

From research, it would appear that the 180 degree thermostat I got was an Allmakes, rather than the Britpart piece I was looking for. I'm not sure that this impacts the final temperature, but I tested the replacement I got with a controllable-temperature electric kettle and the thermostat doesn't appear to be fully open until above 200 degrees, which is not what I was expecting. Hopefully someone has some advice on whether changing thermostats again would solve this problem.

I'm also in the process of building a spray nozzle to clean the schmutz off of the radiator and AC condenser, but the condenser is so old the fins are literally crumbling, so it will probably have to be replaced entirely at some point. Unknown if this is also affecting flow through the radiator.

 

There are several threads here with people buying 180 thermostats that turned out to be 190's instead.
And ordering Britpart and getting Allmakes.
This has made me want to go with an inline mod with a GM thermostat myself.
That way I can be more confident in what I actually have, and replacements are readily available most anywhere.

 

I know it's expensive relative to the price of a stock thermostat, but I'd very strongly recommend getting the OEM soft spring. Don't fuss with Allmakes or Britpart. You can get it at Rovers North. https://www.roversnorth.com/parts/pe...ees_fahrenheit

The bitterness of poor quality remains long after the sweetness of low price is forgotten. Too true with Disco cooling system parts. Stay away from anything URO while you're at it, like hoses and such.

 

A curb isnt steep. Get that front end up, find a hill, embankment etc...

 

I no longer recommend the Britpart 180F which is stamped 78C inside because they apparently don’t exist anymore (if it’s stamped 82C that is not the same unit!!!). Grey OEM, or the 33.00 180F Motorad at your local Auto Zone (if you’re on a budget, I’ve installed several now & zero issues and it is a 180F unit).

 

Good to know. I don't really have an embankment I can use, but I'll put it back on the curb and then jack the front end up as far as it'll go and see if that helps.

Thank you, and that's unfortunate to hear. Do you know what the fully open temperature is on the OEM and Motorad thermostats?