E36 running hot

[dandan]

'Ello,
My daily hack, an E36 318i has recently been running a little hot on long journeys. It doesn't overheat but the temp gauge starts to climb occasionally, if it gets too high for my liking I turn the heater on to hot and it settles back down. At first it was just doing it in really hot conditions, heavy traffic etc, but now it is doing it on a normal run at 70mph and it's slowly getting worse. It's also pretty sweaty having the heaters on full in the summer...

It's not losing coolant and it's well topped up, so what could the possible culprit be?
My current thinking is that the coolant is not being circulated efficiently, so perhaps the water pump is old and tired? Alternatively the viscous fan clutch could be shot? The only other thing I can think of is some kind of blockage somewhere, is it worth trying one of those flushing products first?
A flush is a few quid, water pump £40 and fan clutch £45 so I'd rather not just change them all if I don't need to, the car is only worth a few hundred quid!

Any other suggestions?

[Ralz]

Thermostat not opening fully?

[Mark]

Quick way of testing the fan is to try and stop it (dont use your hands ) if you can its fooked

See if both rad pipes are hot, if ones cold then coolant isnt getting through it, feel the rad all over as well and see if there are cooler areas.

[R3K1355]

I can't imagine the fan would be doing all that much at 70mph, I'd be more inclined to look at a rad blockage or something.

[Mark]

Its quick and easy to check though and eliminates it from the possible suspects

[dandan]

Cool I will check the rad pipes tonight.
I'm not sure I fancy attempting to stop the fan at all, surely if it is working fine it will just get chewed up or broken?

[Mark]

Use something like a rolled up newspaper and gently bring it against the fan in a bid to slow it down. i didnt mean ram a 1/2" extension bar in there

[dandan]

Also, I've just been thinking, the car popped a hose a couple of months back so I replaced all the coolant, GSF gave me blue stuff and i'm reasonably sure I had green in there before, if there was a bit of green left in the system could they react to cause blockages or inefficiency? I ran it for a couple of miles purely on water to get me home so it got flushed pretty well...

[Si]

Bring it over, I'll stop the fan.

More helpfully - blue and green are fine to mix AFAIK, it's when you bring the red/pink gunk into the equation that everything turns into jelly.

[Zornyan]

Quick way of testing the fan is to try and stop it (dont use your hands ) if you can its fooked

See if both rad pipes are hot, if ones cold then coolant isnt getting through it, feel the rad all over as well and see if there are cooler areas.

Not exactly true. I just fitted a brand new oem fan, viscous coupling, thermostat and water pump to my 328i and even after a drive i could use my fingers to bring the fan to a halt. Yet it cools perfectly even on a hot day sat in traffic.

Sounds like either a weak water pump so the coolant isnt flowing fast enough, or a thermostat. The fan does zilch as soon as your moving. Hell you could remove the fan and sit at 80mph all day and it wouldnt make a blind bit of difference.

[BreadBin]

e36 6-cylinder engines are renowned for failing plastic water pump impellers, I'd be amazed if the 4-cylinder ones are any different..

[dandan]

Well it was chucking it down when i got home but I did quickly try to spin the fan as soon as I stopped the car, when it's hot it should be hard to spin, right? well it was very free spinning, so i guess that is borked?
If the fan does nothing at speed then maybe it is water pump, although I'll check for a blockage first as it will be cheaper and easier to fix.
I can't see how the thermostat can be the culprit, surely they work or they dont work, and it's definitely working, as the heaters warm up nice and fast. That said, I do have a spare in my garage so it would be free to swap it out...

[dandan]

Ok I checked the pipework this morning, the higher, right hand (as you look into the bay) hose was hot and the lower left hand hose was distinctly lukewarm, but surely thati s the point of a radiator? That it cools the water flowing through it? I can't actually feel the face of the rad without removing parts so I don't know if it was a uniform temperature.

[R3K1355]

I can't see how the thermostat can be the culprit, surely they work or they dont work, and it's definitely working, as the heaters warm up nice and fast. That said, I do have a spare in my garage so it would be free to swap it out...

To be fair the thermostat on my pug has been removed and I'm pretty sure the rad cap is ****ed, it shows similar problems to your beemer.

I've not bothered to check if it's a blocked rad, but I'm fairly sure it's got shit cooling as there's no pressure in the system.