Overheating... Completely at a loss.

[Codename Duchess]

This has been the week of Rover nightmares for me

LR3 HSE, suddenly started overheated and started smoking coolant out of the reservoir. I shut it down, and happened to be 2 blocks from the dealer at the time.

I had them look at it, as it couldn't move anyway. They diagnosit it as a bad thermostat. I replaced it, and it continues to do the same thing.

I fire it up, coolant reaches a temp of 111 degrees, I shut the motor down and that's it.

I don't see it leaking anywhere, no codes, no noises. There is no action in the top hose, it's just full of air the whole time.

What could this be? Is the rad clogged? Bad water pump? I have no idea how to begin diagnosing this

 

[CMGRover]

Try running it with the coolant fill cap off. It sounds like air lock to me. You might have a bleeder valve but mine broke off somewhere along the line so just open the coolant resevior cap and run it for a few minutes. You'll hear it burp kinda and the coolant level should drop. Top it off if it gets real low. Once it stops dropping that means the air is out.

 

[Codename Duchess]

I've run it with the cap off for a bit, I don't really see any action.

It seems like it's just not circulating at all. Belts seem to be ok, no funny noises.

 

[Codename Duchess]

Ok, followed your advice,

and it seems to be working now. I went for a drive and the coolant temp was between 91-94 degrees.

Is this normal?

 

[CMGRover]

No idea. I've never measured mine.

 

[tlt]

No Action? No water pump? You shouldn't generally change just the thermostat, but the entire assembly, as the plastic junk it's mounted in general falls apart or cracks.

What was done at the dealer?

Pressure cap rating 110 kPa (1.1 bar) (16 lbf/in²)
Thermostat:
Starts to open 88° C (190°F)
Fully open 95° C (203° F)

 

[Codename Duchess]

Hi TLT,

The dealer didn't change a thing, as it was cheaper just to tow it home and do it myself.
Looks like she's running perfect now. I have a monitor running and it never exceeds 94.

I may have been a bit jumpy as I'm deathly afraid of overheating the motor.

 

[tlt]

No problem, but it sounds more like a leak than overheat, as based on your information, it is not even up to normal temperature. Let's step back and re-asses the situation.

 

[Codename Duchess]

OK,

When it initially happened, the temp gauge just started climbing out of nowhere. I quickly shut it down since I was in traffic, I just gingerly started up again, and gassed it enough that I coasted into an open spot at the dealer.

I was quoted a million parts to replace but the pertinent one was the Tstat. I replaced the Tstat, but noticed one of the retaining clips that holds the tstat was broken, and I was unable to replace it.

I replaced the housing (not the entire thing, just the half that holds the stat in place)

after this was done, I fired her up, maybe at about ~80 degrees or so, I opened the bleeder valve nearest the reservoir and the coolant was bubbling out, but not being circulated. I may have been a bit hasty but I assumed that there should have been coolant movement at this point.

So I did as you suggested, and let it run to a higher temp (94 degrees it eventually reached) and it did seem like there was air in the system, I had to add some coolant.

Since then it seems to be running flawlessly, on long highway trips, idling in traffic etc, consistently nothing past 94.

My assumption is the original issue was caused by the housing clip causing the thermostat to be misaligned or something like that. Originally when it broke down I saw a temp of 111 degrees on the coolant.

 

[tlt]

Normally, just replace the entire assembly, which includes thermostat, housing, temp sensor, etc. it's not expensive.

There is a bleeding procedure, which may be tricky. I also ran my heat when bleeding to ensure all hoses where flushed out.

Where are you getting your temperature data?