Good afternoon fellow Rovers,

I recently experienced a peculiar cooling system issue in my 2001 RHD Disco. I've scoured the forum for similar issues, but I didn't find any that quite met the mark.

I live in the Northern Midwest. It's been cold here. On Sunday my kids and I went snowboarding. We drove four hours North to a resort and spent the subsequent two days shredding the gnar. All was well with the Disco on the ride up. However, on the ride down, tragedy stuck. With another 200 miles to travel and the sun setting my heat suddenly stop being.. well heated. My first thought was that I'd blown a line, given the truck is old enough to order a drink at the bar. I pulled over and inspected everything. Nothing seemed out of place. So, I got back on the road. About a minute later my engine temp gauge spiked, so I pulled over again.

It was only nine degrees Fahrenheit, but I braved the blizzard conditions and popped the hood again. This time, I thought it must be the thermostat. So, I pulled the top line, inspected the thermostat, and pushed on it to verify movement. It seemed to be functional and there was no corrosion. I refilled the reservoir, opened the bleed screw for a bit, sealed it up, closed the hood, and along we went with heat and engine cooling all operating normally once more. I thought I was out of the woods.

This morning I fire her up to head to work. No heat. About a mile down the road engine temp gauge spikes again. I pull over, open the bleed valve again (I know that shouldn't help, but I figured I'd try something). Closed up the hood, and drove on. Temp gauge stayed normal, but heat didn't come up. Then, about twenty minutes later. The heat started working again.

Now I assumed it was air in the system. So, I pulled the truck into the garage at work and let it cool off. With some assistance I lifted the coolant tank, removed the cap, opened the bleed valve, and tried to remove any air. But, there really wasn't any, at least not enough to matter. It flowed coolant out the bleed hole like it should. So now I'm puzzled. What causes intermittent heat in the cab, and occasional spikes in engine temperature? Has anyone else experienced this?

Thanks in advance,
The Last One
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Stuck thermo ??

 

@TheLastOne V8 or Diesel - they are two very different engines.

 

V8, sorry. Still getting used to being part of this club. Lol

 

I thought that, @Tomzsix, but doesn't the heater bypass the thermostat? Seems weird that it would lose heat with a stuck thermo.

 

Onset of head gasket failure? What's the bottom of your oil cap look like? Could be that the head gasket is starting to leak, and some combustion gasses are getting pushed into the cooling system, causing trapped air bubbles like you describe.

 

It's a cheap and easy fix. Are you losing coolant?

 

Not substantially. I did order a 180 degree thermostat though, to be sure. Guess we'll see if that solves it.

 

@V50-M66 I'm kind of wondering that. I'm not losing any fluid (that I can tell), but I do occasionally get a Cyl 1 misfire code on start up that rapidly resolves. Makes me wonder if the headgasket is allowing some coolant into the cyl when it sits, and subsequently letting exhaust into the coolant when running. 😑
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Did you order a Rover thermostat, or an inline one? Kind of a waste of time ordering another Rover one.
I know that I have lost cabin heat on all three of my trucks when the coolant level gets low. This has typically happened when the reservoir cap has malfunctioned. Replacing the cap and filling the system solved the problem.