2000 S70 Coolant Temp Gauge Fluctuating

[foggydogg]

Call me crazy, but if it IS a bad stat,
it sounds like the sensor is working just fine.
If it ain't broke...

The maker of the thread mentions it's new to him, and has 335k on it; he'll already be there, juice drained, so it sounds like he's leaning towards doing what I just did on my '98, take three minutes and change it as well. After 23 years the old one deserves a rest.

[scot850]

I agree. Also taking the time to really carefully check the connector for the ECT where it plugs in and it's wiring makes sense too.

Neil.

[454cid]

See 'Somebody...', above, aftermarket clamp and the hose was twisted. Came off without issue. I used a fair amount of heat on the screws, and didn't need the added complication of having the hose in the way. I tend to agree on the radiator side, but the thermostat housing side isn't normally a problem for me.

I wasn't trying to imply you did anything wrong, as your pictures showed you had reason to go further. I guess with mine I've been fortunate to not have issues with the Torx screws AND I've removed factory thermostats (or maybe dealer replaced). I have not had to deal with sloppy/bad previous repairs.

[koolhandluke]

Just a comment on the electrics(dash/radio/ directionals/lights) not working. My ignition switch does not always return to the full "run" position detent after starting (weak spring?), and exhibits the same symptoms. Just nudging it back solves the problem.

[tjmartin317]

To anyone following this adventure, it went pretty well! Worked yesterday, but a slow day in the parts department means there’s plenty of time to work on automobiles.

Would post photos, but I can’t figure out how to do that on mobile. That said, the old thermostat and ECT looked cooked. Black where once gold and just gross. The stat gasket had melted to the thermostat and the housing, hard to tell where the rubber ended and the metal began. A wire brush and a screwdriver took care of most of that.

Despite the fear of stripping something on the way out (even the hose clamp was rusty, but managed to get it loose), buttoning it all back up was a breeze… except for the coolant part.

See, I’m a novice mechanic. And I forgot the basic principle of air + pressurized system = bad. Didn’t bleed the coolant in any way, just topped it off with the green Fram coolant I bought earlier.

We got out the coolant bleeder machine and ran it for a sec, and with plenty of clear BG coolant on hand, we filled it up. Then I ran the car, had to put more in two times before leaving the shop because there was still a shitload of air forcing all the coolant well past the minimum line.

I had to get gas, which is good, because it dropped again. Also learned that my coolant level sensor works after 330k+ miles, so that’s neat.

Threw a bit more yellow Peak coolant in there and went home. Made it without issue. Then decided to get a car wash since I was dripping coolant. Not because there was a leak, dry everywhere I was working and no drips with the motor running… but my aim wasn’t exactly great and there were some spills.

Only after this 30 minute period of commute and car wash, right as. I’m pulling back into the house, did the coolant level light pop on again. Top it off with more Peak coolant since that’s all I got left.

AllData says this system uses 1.8 gallons… it’s felt like I put a lot more in though…

So I guess my real concern is if the concoction of coolant I’m running is a big issue? OEM is obviously best, but of course, my local Volvo dealer is closed on Saturdays. And happenstance forced me to use the coolants I did because I didn’t have a car to get anything else.

Part Peak, part BG, part Green Fram, and maybe a drop or two of OEM from days long gone…

But hey, the gauge does work again!

[FlyingVolvo]

If you want to save a few bucks, go to a NAPA store and get the Zerex G-05 concentrate and a gallon of distilled water. Zerex is good stuff and is designed for the aluminum engines.

It prob won't hurt anything really, but personally I'd want all the same fresh coolant in there. I've always had good luck doing a flush, and then letting the car idle with the reservoir cap off for about 20ish mins as it gets up to temp, and slowly adding in more as the level drops. Like you, even with that method, I end up usually needing to add some more after a little driving, but as long as it isn't critically low, there's no danger.

[scot850]

I also like to raise the front of the car on jack stands as I find it burps better. I still find you can get it burping a few times after that so I always carry a 50/50 gallon of Volvo OE fluid and distilled water for the first few runs and check it before taking off after it has sat ans cooled.

Neil.

[tjmartin317]

Like you, even with that method, I end up usually needing to add some more after a little driving, but as long as it isn't critically low, there's no danger.

You wouldn't consider the reservoir being completely empty "critical danger" after having rolled into the gas station, would you?

I'll definitely be keeping a jug coolant in the car from here on out, and probably just flush the system again on some empty weekend to get better coolant in the engine (may still be a while, I don't have empty weekends until February). Just release the petcock (hehe), let it drain, close it up, and replenish with the engine running a few times. 20 minutes, in your case.

[foggydogg]

The vast majority of coolant sold today is compatible with aluminum engines. Running plain water is frowned upon, so what you have in it is likely fine. As mentioned earlier, don't open the cap until the car has cooled down. Once the system is burped it shouldn't take more to keep the level right; if you keep loosing juice, you have another issue.

[FlyingVolvo]

Like you, even with that method, I end up usually needing to add some more after a little driving, but as long as it isn't critically low, there's no danger.

You wouldn't consider the reservoir being completely empty "critical danger" after having rolled into the gas station, would you?

I mean, it's not ideal... but if you've added the majority of the capacity already, I wouldn't worry too much. Of course, I would still top it up ASAP and avoid driving until I know it's at a good level.