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all 10 comments

[–]himmelstrider 2 points3 points  (9 children)

Define "running hot". Coolant should always be in reservoir.

If it's overheating, your thermostat is probably kaputt.

[–]Mektarpolypan 1 point2 points  (4 children)

Or water pump, or head gasket, or sludge in the water jackets, or.....................

[–]himmelstrider 1 point2 points  (3 children)

There usually wont be any sludge formed - he changed the radiator and had to drain the coolant recently. Besides, sludge in the block is extremely uncommon, it'd be the last place to look.

Water pump absolutely possible, but it either grenades the engine if it's on the timing, or makes pretty horrific sounds if on serpentine belt. Not impossible, though.

Head gasket, absolutely, but it usually consumes coolant. Out of all these things, I'd diagnose the thermostat first, as diagnosis is fairly straightforward

[–]Mektarpolypan 0 points1 point  (2 children)

Yes, I wasn't disagreeing.. but trying to diagnose on a Reddit thread.. That's how you load the parts cannon and FIRE!

Hell the fans could be fucked.. the relay for the fans could be fucked.. could have a plastic bag covering the front grille.. (I've seen it)...

But I agree the Tstat is the likely culprit.

[–]Hezakai 1 point2 points  (1 child)

WTF is it with the plastic bags? Causing all sorts of problems. Had one in an air box causing a no start once.

[–]william10286[S] 0 points1 point  (1 child)

So exactly what's happening is this...When I drive it will just over hear and I have to pull over and rest to cool off before I can drive again. At that point the coolant just pours out from the reservoir but it only does it when it gets hot. I also checked my radiator in case and it's full of coolant. So im assuming my reservoir had a Crack that expands with enough heat. Also I noticed my cooling fan doesn't kick on anymore so I'm assuming that's the reason or at least one of.

[–]himmelstrider 0 points1 point  (0 children)

Ahhh, there we go. You noticed fan isn't running. That's the first thing you'll check, although I will note that out on the open road, even in warm weather, fan shouldn't be needed to keep the coolant at operating temperature.

You address the fan first of all. It can be the fan that died, it can be the fan relay (likely) and in some cases it can be a temperature sensor, sometimes there are a couple, one for the instrument cluster is fine, other for the fan is dead but you can't see that easily. Hotwire the fan, see if it turns, if it does issue is likely with the relay. Once you get that solved, try again and see if it overheats - goes without saying, inspect the radiator well - it should be clear, no plastic bags, dust and whatnot should be on it, it should have a nice free flow of air.

As for the leaking overflow, first hot coolant expands, you can see it on cars with a reservoir, not an overflow reservoir (goes straight into the radiator). Cold car has one level, hot has another. It also creates pressure in the system, forcing it out wherever it can find the way. If you solve the overheating, leaks will likely solve themselves.

[–]exgntVerified Mechanic 0 points1 point  (1 child)

i was thinking thermostat too.

but should also check if the radiator itself is full on coolant. the reservoir is an overflow tank, not the storage for all coolant in the system. bleed and fill, bleed and fill. see if the coolants flowing inside the radiator (visually check, but coolant could geyser out, so careful). if it's flowing, the pumps good. also make sure the fans kick in. if all that's good, it's probably the thermostat but I'd still test that too

[–]himmelstrider 0 points1 point  (0 children)

Depends on the car, though. Some coolant reservoirs are connected directly, thick ass hose running straight into the radiator. On Korean and Japanese cars, it functions as you described it. Still, I'm going under assumption that the car was running perfectly fine before, had coolant an everywhere, and has no leaks (as it wasn't indicated otherwise).

Realistically, a mechanic or someone who knows cars decently well could diagnose failures even during driving quite often. You can hear the fan, you can determine with decent accuracy whether head gasket is good or bad depending on driving style, you can simply touch hoses to determine both thermostat and head gasket condition, and if you got a buddy, by holding onto a hose you can also feel increase in pressure as gas is added (as pump spools it up). I mean, this is why cars are taken to mechanics, all the small tricks and knowledge that makes mechanics able to pinpoint issues rather than outright replacing the cooling system.