Heh... 1 hour in a traffic jam -> overheating engine

[TB2]

Well, we just wanted to go to a party on the other side of Hamburg, so we took the highway. Right when we pulled on to the high way, we were already stuck. And after about 45 mintues we've already seen 4 different cars (two of them recent BWMs) on the side of the road with the bonnet opened. I was already joking "yeah, that happens to be a problem when there's no airstream". But then after one hour, a blinking orange light came on on the right side of the dash, and just before I managed to make my way to the emergency lane, a second big red light went on together with the STOP light. heh well...

"That's not supposed to happen"

I was wondering why the fan didn't take care of the heat, but when I had a look down the front, I noticed that one of the fans (the one that usually is turning), had fallen off the motor! It's just sitting there in its cage, detached from the center.
Tomorrow or Tuesday I'm going to do the rear arm bearings, so I'll have a chance to have look at the fan. I guess I'll just have to re-attach it somehow.

Well. I guess it's no biggie, just felt like telling a tale

But, why are there actually two fans? I usually only see one of them (the broken one) turning when the engine is getting hot. What's the other one for?

[toddao]

But, why are there actually two fans

For when it gets hot,hot, hot.. feeling hot hot hot

[mat_fenwick]

There are two switches within the cooling fan 'switch' (on the radiator by the alternator) - one makes contact at a lower temperature and should bring on both fans wired in series (both get 6V and turn slowly). If the temperature is still increasing the second part of the switch makes contact and connects the fans in parallel (both get 12V and turn fast). My guess is that there is a break in the circuit for one motor (therefore neither will work on the slow speed setting when in series), and the only time you hear a fan is when the engine is really hot, and both should be turning fast.
I hope your head gasket is OK after the 'red lamp of death'

[Jaba]

Yea you should deffo get both fans running together at low and high speed.
It is worth checking your fuses as there is a fuse which blows on aircon BXs that prevents low speed fans from working at all and then at high speed only the right hand fan spins. Perhaps this is your other problem as well as the obvious rotor off, a faulty fan could have blown the fuse.

Viel spass

[kiwi]

But, why are there actually two fans? I usually only see one of them (the broken one) turning when the engine is getting hot. What's the other one for?

You got Aircon fitted? But then knowing the BX they probably put it in the for the "option".

My 19TZS has dual Fans but it has Aircon the 19TRS does Not as far as I can recall all the BX non Aircon models I owned had a single fan.

It is possible that the second fan is not electrical connected because of it being non aircon?

Going to echo Mats comment as well about the Red Lights of Death coming on! One of the reasons we prefer Temp Gauges (insert disclaimer I have not got a gauge either) is because once those lights come on its pretty much to late. Fingers crossed.

[TB2]

It is worth checking your fuses as there is a fuse which blows on aircon BXs that prevents low speed fans from working at all and then at high speed only the right hand fan spins. Perhaps this is your other problem as well as the obvious rotor off, a faulty fan could have blown the fuse.

Oh that is very interesting. This could very well be the case, I only ever saw one of the fans spin, and I have an air con fitted. I'll check all the fuses.

I hope your head gasket is OK after the 'red lamp of death'

Is it that serious? Well the red lamp was only on for about 3 seconds right when I pulled on to the emergency lane, after that I immediately switched off the engine. We then waited a couple of minutes while I inspected the broken rotor and after that we pulled off the highway and went through the city streets to our target at proper speed to have some airflow. On the way back, we took the high way which was clear and I had no problems driving at 100km/h.

Well, fingers crossed, I'll inspect everything tomorrow or the day after tomorrow. I'm confident that my good old lady dodged a bullet here

[mat_fenwick]

My 19TZS has dual Fans but it has Aircon the 19TRS does Not as far as I can recall all the BX non Aircon models I owned had a single fan.

I think it is just the TD engine (and perhaps the valver?) that have twin fans as standard if no A/C is fitted.

[kiwi]

I have an air con fitted. I'll check all the fuses.

Thats why you have two fans then

I hope your head gasket is OK after the 'red lamp of death'

Is it that serious? Well the red lamp was only on for about 3 seconds right when I pulled on to the emergency lane, after that I immediately switched off the engine. We then waited a couple of minutes while I inspected the broken rotor and after that we pulled off the highway and went through the city streets to our target at proper speed to have some airflow. On the way back, we took the high way which was clear and I had no problems driving at 100km/h.

Well, fingers crossed, I'll inspect everything tomorrow or the day after tomorrow. I'm confident that my good old lady dodged a bullet here [/quote]

Switching the engine off would have switched off your warning lights so if you had kept the key in the accesory position you would have probably seen the light stay on a lot longer than 3 seconds.

I have had a Headgasket problem that took nearly a year to really show itself. The loss of coolant was only noticable on short trips or after standing for prolonged periods (ie days). Big give away was being parked up for 3 weeks and it would no start because a cylinder filled with water. On our Van it was pretty clear the head was gone (a diesel) because it had lost all the water when a hose went on a steep hill in the rain.

You may have dodged the bullet or may not! Just my fingers are crossed for you that you have a ultra sensative warning switch and the alloy head did not distort.

I know this sounds negative just dont be surprised and keep an open mind on the possibility of a head rebuild.

[TB2]

Yeah well, if it's the head gasket, then shit happens.

Just wondering, what *exactly* happens when the engine overheats? Why does it blow the head gasket? Is it the weakest point in the engine and "intended" to go first to prevent any serious damage to the engine? You said "the alloy head distorts"?

[kiwi]

I wish you had not asked so might try and see if I got the reply right or at least on the right track.

THe Headgasket acts like a pressure seal and like all gaskets is the weakest point. Over the years they get fragile as well and inclined to fail through corrosion.

Alloy head distortion is what I have been told in the past is that the head is made of Alloy which over a ceratin temperature distorts hence why we have a cooling system in the car.

Basically I aint got a clue I just know that once the Red Light of Death comes on the BX that its the start of interesting times.

My Korean Astra when we got it had a problem with the thermostat switch (an electronic gizmo) she got to hot under load (ie going up a Mountain) she would simply backfire and die. Happened a couple of times watched the temperature gauge go up and pfft engine cut out. Eventually struggled with the modest of hills until we got it replaced! It acted like a safety switch something I dare say the BX could use because this little Car is still going today.

I have only seen the red lights of Death on one BX we owned and thats cooling system was severly stuffed. When they took off the head the gasket was pieces and the head was so badly twisted it could not be skimmed. Extreme I know but I was told a result of the Red Light of Death!

[TB2]

heh... Got a feeling there's going to be some fun times ahead. Well, one step at a time, going to fix the fan tomorrow. And the rear arm bearings after that.

Had a look at prices for head gaskets. Kinda expensive. And they want you to buy a set of "head gasket screws" for the same price as the gasket itself. Though until now I have not felt any signs of a blown head gasket. We'll see, we'll see. This car is full of surprises.

I still love it

[citronut]

try running a 12V suply straight to the other fan and if it runs corectly you could just swap it over for now, it will be better than nout, quite offten the terminal conectors tucked just under the edge of the bumber below the head lamp/s become tarnished/green, try just giving them a clean for the fan which did not run

regards malcolm

[mat_fenwick]

In a nutshell, the aluminium of the head expands more than the iron block. Within a certain temperature range this is OK, but once things get too hot the head will distort enough so that it no longer supports the gasket, and hence the HG fails.

[kiwi]

Had a look at prices for head gaskets. Kinda expensive. And they want you to buy a set of "head gasket screws" for the same price as the gasket itself. Though until now I have not felt any signs of a blown head gasket. We'll see, we'll see. This car is full of surprises.

I still love it

It is still cheap and I did ask about the necessity about not having to replace those bolts on here before and with my mechanic. The reason is simple they are designed to tension the head and because of that tension the bolts stretch with the constant warming and cooling. Head off no matter what is new bolts!

Ok so it is not cheap but then it will last longer if you do replace them!

[mat_fenwick]

The reason behind stretch bolts is to try and get uniform clamping pressure on the head. By torquing up a bolt to a specific torque, you will get roughly the same clamping force on each bolt, but this can be affected by thread fit/cleanliness etc. and is not very precise. If you think about it, if you tighten a bolt until it starts to give, there is no more clamping force that can be applied. So if you tighten all the bolts till they are stretching, then (assuming they are all heat treated the same!), clamping force will be equal across the head. I also think it would have something to do with ease of manufacture of the engine, as so long as the bolts have been torqued till they stretch, it doesn't matter as much what the actual torque was...