mikeloc24

Do any of you know what/where the fan switch sensor is? I'm still dealing with the darn overheating issue even though I replaced the radiator, fan clutch, thermostat, and water pump all within the last 8 months.

What the car (92 SC300) will do is this (these aren't my words but the words of a fellow member who was experiencing the exact same thing on his ES): "The temperature when workin right, is right above the second line on the guage; right at halfway. Recently, I can drive it for a while (usually 30 minutes or so) in the city, on backroads, the highway, wherever without any trouble, but eventually the temperature begins to rise. Usually it'll go back down momentarily, indicating the thermostat opening and closing I suppose, but after a while of this, it will go sky high at which point the system can't recover and I have to stop and let it cool down. I've visually checked the thermostat and gasket, as well as tested it and it works just fine. The cooling fan also appears to work alright (it runs continuously at a slow speed and speeds up as temperature goes higher. stays on full blast when it gets really hot). The cooling system has no leaks, and as I said earlier, the radiator is new. One thing I've noticed is that when I very first start the car, I can hear the sound of rushing water behind the dash (possibly air in the cooling system moving through the heater core my dad says). Also, as the car is running, the coolant overflow tank will slowly fill up above the full line till it's almost full, but the temperature is still normal. Performancewise, the car still drives 100%."

I read a thread where it stated the issue was the fan switch sensor but I can't find any more info on the subject no matter how hard I search. Anyone, someone, please chime in with your experiences with this particular part. I have found out that the part number is #89429-24020 for the SC300's. Thanks.

damn damn damn (again).

mikeloc24

Eugene, my car is doing the opposite of that. At idle it will start to get hot, I will watch as my temp needle slowly starts to rise. This happens while I'm stopped at a light or what have you. Once I start moving and I press the gas the temp will creep back down, this cycle continues whenever I stop and start. I have a new Modine radiator that's less than 8 months old, new water pump, new thermo, new timing belt, t-belt tensioner, all that crap I replaced. I even bought a new fan clutch.

I hear the rushing water sound behind the dash in the mornings when I start the car up. I know someone else who has/had an SC300 has to have dealt with this before. My SC can't be the only one to have this issue. Every other common issue with these cars has been covered, this one has to be included in that group. I can remove the radiator car (that's new as well, less than 2 months old) and let it idle and add coolant and see what happens. I do play to buy this stupid part (fan switch sensor) and install it this weekend, but before plunking down my money I wanted to make sure this was the fix...no one seems to know. Any other suggestions?

PERRYinLA

Mike, I don't have the same engine as yours, so don't take this as gospel, but I did have some overheating experiences with my BMW 3.0cs that I thought I'd share. Understand that not everything applies in your current case:

The inline six gave me over-heating problems on 3 occasions. The first time, the water pump had too much clearance between the housing and the impeller blade, allowing too much coolant to "slip" through the gap and decreasing the efficiency of the pump. Once I placed it in a press and closed up that gap, no more problems.

Until I got air in the system, which collected at the thermostat housing, surrounding it with air and keeping it closed when it should have opened. There was a very convenient bleeding screw to let the air out. Not sure if your 6 has that or not. I also remember taking the thermostat into my kitchen and placing it in boiling water, to test when it opened/closed. One winter I was very desperate and just removed the whole thermostat and blocked off half the radiator. It took longer to warm up that way, but otherwise ran fine for a few weeks till I fixed the pump as described above.

Eventually, my head gasket developed leaks, that under high throttle would leak some coolant into the cylinders, depleting the coolant and overheating the car- you can't live with that sorta problem too long!

But when everything was working right, I didn't even need the fan unless I was stopped anywhere for more than 2 or 3 minutes.

If a bad fan switch is indeed overheating your engine, that means the fan is not on as often as it should be- one good test would be to just lock up the fan, period. Then it spins all the time. I have the V8 with the hydraulic fan, so I am not sure how your stock fan works. I don't know if you can lock it up mechanically with some bolts or electronically by bypassing that switch, but if you can, try that for a while and see how the car behaves.

In my opinion, a coolant flush (as opposed to a bleed) almost never solves an overheating problem. A properly working cooling system would work with just water in there, and in your case, you recently replaced the water pump, so you have seen the coolant recently and unless there was rust or lumps of sludge in there, the coolant is not a factor in the overheating issue.

mikeloc24

Perry, yes when I had the new water pump put in the coolant was also changed and it was in excellent condition.

Let me ask you, as well as other members this question, should there be even the slightest amount of coolant visible on the outside of the water pump? When I look in my engine bay at the pump I can see coolant dried on it (it looked dry but I didn't actually reach down there and touch it). I asked my mechanic as well as another member and they said that's normal. But for some reason in the back of my head I keep thinking it's not normal, that since the pump and gasket are new I shouldn't be seeing ANY coolant at all on the outside of the pump. I checked my coolant level and it seemed fine so now I'm stumped. I don't want to screw around with my fan in an attempt to "test it out" because the fan clutch is brand new as well, that's what's pissing me off about this whole situation...the bulk of my cooling system is barely 8 months old (thermostat, water pump, radiator, radiator cap, coolant, fan clutch) so why I'm hvaing overheating issues is beyond me....damnnnnnn!

Anyone at all ever experience this? Is it possible the water pump isn't on snug enough (strange as that sounds)? I know my mechanic so I know the work wasn't performed by an idiot, but could there have been something missed?...I don't want to buy this "fan switch sensor" thing unless I know it's the right fix for this problem.

SPORTcoupe

iTrader: (2)

Ok....digging up an old thread here.
I've got the exact problem that was described by your ES friend.
Mike, can you refer me to who this member is?
I'd really like to know what, if any solution he came up with.

Did you end up resolving your issue?

Cheers,
~Alan

Supra Dr

iTrader: (14)

maybe you should post your specific problems, whats been tried & tested.

the fan switch is a mystery. the SC uses a cooling fan clutch mounted to the
water pump. the ES has a transverse engine & uses a electric or hydrolic
cooling fan system. the electric fan system uses a coolant fan switch.
n/a on the sc model. the guy w/ the BMW also has electric cooling fans.

john

PERRYinLA

Let this guy advise you that the BMW 3.0cs does not have any electric cooling fans, and never did. Its fan is driven by the water pump pulley.

You're confusing it with 3 series- different cars, different generations.

Supra Dr

iTrader: (14)

sorry perry, missed the 'cs' & of course you are correct about the fan clutch.
thats a nice old girl, back when cars had style, instead of the cookie cutter designs of today.
anyway, what happened to our thread bumper?
john

SPORTcoupe

iTrader: (2)

Sorry about my absence...work is kicking my ***.
Where to begin?

I bought the car 2 months ago in Houston, TX from a reputable Z-car mechanic who in turn bought it from an old Asian guy based on good word from another mechanic who has been servicing the car.
I got 80 miles from Houston when the temperature gauge began to climb slowly above the regular level.
I pulled over and popped the hood. I realised now that after everything I checked on the car before handing over the cash, I had forgotten to check the coolant (level/color)
The coolant was at a pretty high level (expected when the car is pretty darn hot) and a really disgusting brown color with hints of rust particles in it. INFO: The car is a 95 (OBD-I) and I'm being told that Toyota didn't start using their proprietary Red coolant until 96, so this car was supposed to have the green stuff.

I drove 30 more miles with my eyes glued to the temp gauge and stopped at a WalMart when it started to heat up again. I bought some basic hand-tools and after waiting like half an hour for the car to become cool enough to work on, I took out the thermostat. Since at this point I knew little about what a failed thermostat is supposed to behave like, I took it back inside WalMart and used a pair of wire cutters to take out the middle part (essentially making sure the thermostat is always open)
I stuck the disk back in, topped off the radiator, and got back on the road.

Everything seemed fine for about 120 miles but then to my susprise, the needle started rising yet again. I did the stop(wait to cool)-go-stop(wait again) routine through the night and in the morning (Saturday) I pulled into a local middle of nowhere auto shop just to find out it's closed and I was pretty excited when the mechanic picked up his cell phone, but disappointed when he told me they were at the racetrack for the day, and that the next shop is like 50 miles away.

When I got to the next shop, a very nice technician took a look at it, and started scaring me with his "it could be the headgasket and air is getting pushed into your cooling system...blahb....blah"
After I explained to him my sticky situation (that being the fact that I was 1500 miles from my home in California where I had to be on Sunday night) he called a friend of his who happened to be a "Toyota guy".
When this guy shows up about an hour later, he tells me to turn on the car.
It runs for about 5 minutes while he's listening, touching, and smelling it. He asks me to rev it for a litlle while and checks for pressure in the cooland hose. Then he tells me to turn off the car.
As soon as the fan stops spinning, he sticks his hand right in between the blades, and touches the radiator right at the middle. I realised before he even said anything that if he was able to keep his hand there for a few seconds, the radiator must have been cold.
So now I'm being told I have a clogged up radiator and will have to wait till Tuesday to get one in.
I had to be at work on Monday. The scenario they were proposing was out of the question.

I used the hospitality of the shop to do a radiator flush on the spot. Not much came out, but I had to leave, especially if I had to make as many stops as I though I would.
Surprisingly enough, from there I made it home with no huge problems. It was still running a little hot, but not overheating.

I drove around in this condition for about 2 weeks, but then it started getting worse and overheating again.
I then swapped radiators with my other SC (which had a perfcet cooling system) and put in a Tom's thermostat (70 degrees Celcius)
This seemed to make the problem go away but once again, only for a few weeks.

So here I am.
Last night I pulled over on the side of the road after driving on the freeway and starting to overheat. I braved it and stuck my hand down the radiator like the guy had done weeks back.
The top of the radiator was boiling hot, and so was the bottom, but the middle was luke-warm at best.

I've made a few assumptions, but they have no backup because I a)don't know the cooling system well enough AND b) don't have the equipment to pressure test the system
My assumptions are:
1) Water pump is weak and unable to pump the coolant through the whole radiator I am assuming here that there are easier and harder paths through the radiator, and a weak flow would use the easy path
2) Air is somehow getting into my system and causing air-bubbles to form which makes the car overheat, dump coolant, form bigger air-bubbles, overheat worse This would explain the fact that after filling the coolant completely and topping off the reservoir, the car runs well for a few days at least.

My hands are starting to hurt....I'll leave you guys with this.

Let me know if you have any ideas or ask things I haven't mentioned.

Cheers,
~Alan

PERRYinLA

Like I said in another thread, overheating problems could have many causes so you run the chance of looking silly when the real cause is identified, but thanks for being very descriptive with your problem.

In this case, I hope I do look silly and I am wrong, but from how you describe it, my most likely guess is a blown head gasket. That's why you can go for hundreds of miles without problems, and then all of the sudden you start overheating. The head gasket is holding up most of the time, but after a while, for whatever reason (like flooring the gas pedal to pass another car), it starts leaking and you lose coolant in the system. Eventually you lose enough to start overheating.

Another possiblilty is a leak elsewhere in the system, but you probably would have found that by now. Or maybe your cooling passages are so full of deposits that you have clogged up two radiators? I hope by now you have flushed out all contaminants. Worse case scenario would be a cooling system so neglected the passages are corroded and/or clogged.

As for the water pump, it's hard to imagine it's defective if it worked fine for 120 miles.

Supra Dr

iTrader: (14)

yuck, possible multiple problems from neglect. correct me if i'm wrong but toyota's been using red coolant in everything since the 80's. i beleave my '81 pick up had red & my '85 celica is
definatly red. none the less green is fine.

i think we can rule out a fan clutch problem since its overheating on the highway.
the t-stat's new & rated @ a lower temp than the original.
your sure the "new radiator" is in good condition & free flowing?
have you been monitoring the coolant level daily? if the head is leaking & sipping down
coolant, you may not notice till its low enough to overheat. then your not sure wether its low
from a leak or from the boil over. i think a pressure test of the coolant system is 1st.

headgaskets are a PIA to diagnose in the beginning stages. its possible the clogged rad. , acidic/old coolant & repeated overheating has damaged the headgasket.
you could try & pull the plugs to see if 1 or more is completely clean (no carbon) or white ashey.
the proper test is a compression/leak down check w/ the engine hot & coolant under pressure.

if everything still checks good, we're back to the old rotten fins on the water pump. i've seen it
more than a few times & there's NO shaft play on the fan side of the pump. the fins actually are
rotten & do not move the water as you would expect.

these types of problems are the "never ending story" & one day it gets resolved.

when you do resolve it i would flush the coolant every 6 months unitl its spotless, you really
dont want the heater core to take a dodo.

good luck & keep us updated
john

rscott

if the middle is cool, im going to bank on it being a circulation issue over it being a blown headgasket to keep things somewhat optimistic. With that my assumption would be it is probably the water pump. If there isnt any movement, it would make sense that the top and the bottom are hot since those parts are closest to the engine and the middle cooler part is the part most exposed to the cooling air.

Unfortunately, what usually accompanies long and drawn out temperature issues is either a blown headgasket or at worst a warped head. The first thing to do would be to check the oil to see if its milky. Also, after it cools, check the level of the coolant. If its not up where it should be, then the coolant is leaking somewhere it shouldnt be. If it is level, but you have some oil droplets swimming at the top you PROBABLY have a blown headgasket.

Im not sure how a water pump could be tested, but thats where im putting my money. Also, a clog something doesnt necesarily mean a clogged radiator. it really can be any of the hoses. Try doing a full system backflush. you can get the kits at walmart or your local parts store. the kit has you cut a heater hose and insert a T pipe that you attach to your hose. Run that for a while per the instructions and try changing the coolant again.




Ghosts in the car are never fun....good luck with it.

Supra Dr

iTrader: (14)

agreed w/ both rscott & perry in la

had a brain fart & remembered alittle backyard check for the water pump. its not 100%
conclusive, but would give you an idea of circulation & trapped air.

the tool companys sell this for about 20.00 & possibly pep boys or others. its a coolant
fill bucket kit. its comes w/ adaptors that fit on the radiator in place of the cap. the "bucket"
fits on to the adaptor. you fill the bucket to about 1/2 way, now that coolant level is the highest
point of the entire system. gravity & flow will work out any trapped air in the system, including the heater core.

this could help you buy providing a save way to watch what the coolant is doing & not introduce any more air to the system. we use this all the time to top off the system after service. some types of cars are notorious for trapping air in the heater or maze of piping running everywhere.

how to check for your problem: fill the bucket to a level higher than the heater hoses @ the
firewall. run the engine till its up to temp & your sure the t-stat is open. (upper/lower hoses
equally hot) you may have to keep adjusting the level as the air gets worked out. at idle you
may see alittle movement, at a steady rpm (say 1500) you should see more action. if you
rev the engine up/ down the level should lower & rise. this helps show the health of the water pump. as its being rev'd up the impeller creates a vortex & the level should quickly drop in relation to the change in rpm. in english: if you go from idle to 2,000 rpm in 5 sec. the level
should substancially drop. if the water is just laying there or very little action the pump is more
likely the problem.

i will admit i've removed more than 1 water pump to perform a visual inspection. unfortunately
thats the only 100% way to know.

john

SPORTcoupe

iTrader: (2)

Hey All. Thanks so much for your opinions!
I did quite a bit of driving this weekend and have come up with the following:
1) If I drive the car at a steady ~2900 RPM (~75 MPH) without large changes in throttle, eventually it starts to overheat. I think this is a good sign (not the HG) but I'm not 100% sure
2) Filling the system up completely now has a lesser effect (meaning it doesn't last as long) than it did before. This points me to the possiblity of the degrading performance of the water pump.

I had a really awesome friend/mechanic, but as it happens with most mechanics who are too nice, he got burned a few times by ****ty individuals, and he had to sell the shop. Now I am without a trustworthy mechanic and as you all know, they're few and far in-between.
I have a lead on a possibly good mechanic (he's only done 1 job for me but was highly recommended by a good friend. the downside is this friend knows nothing about cars, so his reccomendation counts as only half) The problem with switching to a new mechanic is the lack of trust in BOTH directions. I don't quite trust him to know what he's doign and use my money wisely, and he doesn't trust me when it comes to diagnostic of problems, which means he's doing things (labor time) that I've already done.

I'll definitely try the "bucket" (will have to do some more reading first) because I know that air bubbles are not your friend when it comes to cooling systems.

After that my order of tests is:
1) Coolant pressure (shop?)
2) Compression (self)
3) Leakdown (shop)

If all of the above look good, I will not feel as bad throwing down the $$ for a water-pump.
Wish me luck.

One more thing I should add, although I'm not sure whether it's relevant: two weeks after the car arrived back here in California, the turbo was swapped from my other SC onto this one.
The turbo setup was transferred over without any changes, and it didn't cause any cooling issues on the other SC, so I'm thinking it's a constant variable, and therefore irrelevant.

Oh, and don't feel too sorry for me if it does happen to be the headgasket. I've got a TT gasket and a set of 525CC injectors sitting here waiting for a good opportunity to be put to use.

I'll keep you alls updated. =)

Cheers,
~Alan

EDIT: It's getting later in the night now so I quicly scanned the posts one more time and realized that I should answer the two important questions:
1) Engine oil is absolutely clean of coolant
2) Coolant is absolutely clean of oil

Supra Dr

iTrader: (14)

good luck