minor coolant leak?

You don't need to drain down completely, but you do need to drain at least 3-4 litres if you don't want any spillage.

Personally I wouldn't bother - I'd just put a tray under the front and undo the hose.

If the coolant is more than a year old drain it down and replace while you're doing this - it makes sense.

I think the coolant is more than a year old, so I guess I should just drain it. Is it necessary to flush the system also, or is simply draining it usually ok?

Also, what else should I do while I have it drained? Should I replace rusted clamps or old hoses, even if they're not leaking? I was also considering putting in a cooler thermostat as suggested on the townsendimports site, since my c900 displays the symptoms of getting very hot after highway driving.

Speaking of that- is the replacement thermostat really necessary, or would it be sufficient to replace the fan temp sensor and/or rewire to make both fans come on when the AC is off? I've been thinking of doing something like this for awhile, because it really does get quite hot when sitting in traffic (esp. after highway driving) when the AC is off.

Also, since this is an epic post anyway: My heater works very well when I'm driving around, but when the car isn't moving only cold air comes out. What gives?

Thanks,

John

Well, it all depends on how much you like doing routine maintenance! I would flush both the radiator and block with a hose whenevr I drain down. Is it necessary? Depends on the condition of your cooling system.

I don't normally replace hoses unless they need it. Check the hose for any signs of cracking. The radiator top and bottom hoses are the most likely failures. If there are any signs of surface cracks, then replace.

Good idea - but how hot is very hot? You may have another fault causing the overheating.

The thermostat and the fan stat do totally different things. The thermostat controls the engine's temperature by controlling coolant flow through the radiator.

The fan helps the radiator lose heat when there is insufficient air flow through it.

At speeds greater than say 40mph, you already have all the airflow you'll ever need. If your car never travelled slower than 40mph, you wouldn't need a fan at all. Doing anything to the fan stat, or wiring in a second fan won't help you if you're overheating at speed.

Sitting in traffic is different. Get a lower temp fan stat.

Does this coincide with the engine temperature being really high? It's supposed to work this way. When the engine is really hot, all coolant is pushed through the radiator, to achieve the greatest temperature drop.

Ok. Having never done this before, I must ask: how do I dispose of all that used coolant? Dumping it in the street doesn't seem like a good idea.

It get just short of the red, but it has never actually overheated. The fan kicks in at that point, and it gradually cools down to normal. Then the fan goes off, the temperature slowly creeps back up, and the cycle repeats. Turning on the AC (and thus the other fan) keeps it at normal temperature consistently.

Ok, sounds like that would indeed fix things. Do I need to drain the coolant for that, or can I do it seperately?

Ah, good point. That might explain it. I'll see if there's a correlation.

John

Some enviro types won't agree with the following - As an ex-chemist, I have a realistic understanding of the dangers of ethylene glycol. Discharging a small amount to your sewer won't do any harm. If you're worried about it contact your local authority and check with them.

Is this while travelling at speed? Either way, your fan is kicking in too late. New fan stat.

You'll need to drain about 2-3 litres to do the thermostat. Do it at the same time, it makes sense.

Of course, maybe I should be less concerned with my cooling system and more concerned with my exhaust, seeing as my muffler just rusted off tonight...

Although honstly I think the car sounds much better without it :)

John

Nope, only when sitting in traffic.

I was really asking about the fan stat, not the thermostat...

John

Ok, definitely fan stat.

A bit more than the thermostat, because it's slightly lower down.

Ok.

Thanks for the excellent input.

John