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1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Paul,
I thought I had been there (and done that), but on the 2nd sight you issue differs from mine happened with Aeroflop. Well, lemme brake it down and I think you'll see what you need to do. So how stuff works:
- there's a heater that heats up the fluid (the engine)
- there's fluid that TAKES the heat from the heater (engine) and PASSES it on to heat-dissipater
- there's a pump that make the fluid go round (the water pump) that is belt-driven
- there's a thermostat that IS to maintain the temperature at specified level. Once again: it's not the fan or the fan sensor or anything else, it's the thermostat that's primary objective is to maintain engine temperature at specified level
- there's radiator that dissipates the heat and there's 'closed loop' that saves the heat. The thermostat either fwd's the fluid to radiator or to the 'closed loop' to run the temperature
- there's an ADDITIONAL fan that runs an air thru the radiator when air-flow isn't enough (e.g when you stay still or run slowly). In order to save the heat the fan is run only when temperature is high enough (either by means of temperature sensor or via visco-clutch)
- there's a control system for a driver to monitor the system performance. It's a temperature sensor (in most designs it's another sensor, not the same one that drives the fan) and a temperature gauge in instrument cluster
N.B #1: we take the additional stuff like cabin heater and engine heat-to-air dissipation out of the scope.
N.B #2: the fluid is the actuating medium of the heat transfer process. Why? Cause an air or a steam do not take a heat and give it back that great as a fluid does.
N.B #3: the cooling fluids that we use for our cars require an additional pressure to be able to work that those temperatures that they work with: usually it's about +1 bar (eh... 14 psi or such). If there's no that additional pressure then the fluid starts boiling up and instead of having fluid cooling system we come to smth like fluid-and-steam cooling system. A cooling system that is designed to work with a fluid does not work well when it works with steam. Honestly, it works poorly in such conditions.
N.B #4: that additional pressure is gained from nothing - there's no special compressor. It's just the physics: if you warm up smth (smth solid, smth fluid or smth in gas phase) it extends. If we keep the volume constant (those rubber hoses do extend a bit, but it doesn't play that much here) then we rise the pressure up. Simple! And it's the pressure valve in the cooling tank cap that keeps the pressure at the specified level.
So...
First of all, thanks for reading. Even if you do not respond to this post I'm still hoping for the best and assuming you read all the moonspeak of mine really cheers me up and encourages.
Secondly, check whether the temperature is indeed that temperature as you suppose it to be according to that needle. In my case (the system worked almost as it supposed to do, except that the needle tended to run close to red zone - but my fan didn't come up only for 3 secs, it run as most fans do, for about 20-40 secs each time depending on what was going on around) it was the sensor that was fooling me. Bentley says that the perfect sensor should have about 50 ohm of DC resistance at 100 C degrees (putting those specs off my head, pls check with Bentley - I can be wrong, I do not trust my memory any more). Definitely it's hard to check (unless you really like to work with boiling water), but luckily those sensors are pretty much available and you don't need to break you piggy bank to order one. Have that sensor replaced. If your (old) sensor is (was) fine then...
3-rdly, what does it mean that your fun runs in for 3 secs and shuts of right on the 4th sec? It means that (let's assume that the sensor triggers itself on at Th=94C and off at Tl=90C - those digits can be wrong but it doesn't play that much here) the cooler's (radiator+fan) performance is enough to cool it down from Th to Tl in three secs. How can it be? Well, you may have NASA-designed fan. Or a veeeery thick all-copper radiator. Or... That the fluid-flow thru the radiator isn't that much comparing to radiator heat-exchange and fan air-flow performance. In other words: you've got cogged (internally, the fluid-flow is lower then it's expected) radiator! Have it cleaned (or replaced in a case you've got a spare on somewhere on your shelves) and you should be good. Though it may be worth starting your repair with belt-check (tension) since it's the belt that runs the pump and it's the pump that gives the fluid-flow.
Zig
P.S.
I can be wrong about the resume, but I did my best to be very accurate at basics description. Please read them carefully and I'll be glad to know that you come to the right decision while mine is wrong. And get back telling what was the issue.
posted by 77.37.1...
, Sun, 13 Jun 2010 14:14:02
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