'89 BX 16V overheating on standstill?

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krekov
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'89 BX 16V overheating on standstill?

Post by krekov »

Hi, my second topic here! It would appear that my BX is now running correctly, but it seems to overheat in traffic.
I say "seems", because I don't know if I can trust the gauge.
The temp. sensor is new, and so is the thermoswitch for the radiator fan.

This only happens in standstill or traffic, my gauge moves up to 110 (without getting into the red zone) and then it goes down, as the fan kicks in at full speed. It does turn on at half speed earlier, but that happens only just before 110 on the gauge.

Likewise, it switches back to half speed after cooling down to about 100-95 on the gauge. I even fitted a switch that closes earlier, at 88C and 92C respectively, but it didn't help at all. The fan starts going earlier but the gauge still moves up to around 105 and just stays there, like the half speed fan has no effect on cooling.

When driving for prolonged periods of time on the motorway, even at around 150km/h, the gauge stays at 90. It goes back down to 90 pretty quick once I start driving after standing still too.

So, is something wrong with my cooling system or is this normal? I consulted a mechanic on this issue and he said that's just how these cars were.
Also, I have only one radiator fan. Did the 16V models have two?

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Re: '89 BX 16V overheating on standstill?

Post by RobC »

They do run hot yes. Do you know the condition of the water pump? Fit another fan if you can. Perhaps also swop the warning switch on the block for the one that triggers the initial orange light on lower model BXs, then you’ll get a more timely warning in case of actual overheating.

What’s your oil temp gauge saying? I’ve found some oils run hotter than others. I stick with Total Quartz 10w 40 (as originally specced) and that seems to keep the oil temp lower than other oils, which all helps.
1991 Citroen BX 16v

RobC
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Re: '89 BX 16V overheating on standstill?

Post by RobC »

PS if the half speed fan is having little effect on cooling then it may be that your radiator is a bit clogged or the fins have perished.
1991 Citroen BX 16v

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white exec
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Re: '89 BX 16V overheating on standstill?

Post by white exec »

Is the half speed (via its dropper resistor) reasonably brisk, or a lazy draught?

For a 16v, I would have thought twin fans would be needed.

This is what Parts shows for the 16v (16S) — a full width radiator and twin fans:
.
BX 16v radiator.JPG
BX 16v cooling fans.JPG
Maybe check the actual engine temp with a non-contact (infra-red) thermometer, aimed at the thermostat housing (water outlet).
Agree about the rad maybe being iffy. Is it the right one for the car (some were larger than others)?
_________

If you want to upgrade to twin fans, I have the circuit for operating them (from the existing thermo-switch). It uses 3 relays, working together, and no dropper resistance. Two fans operate (which must be of the same type) in series for Slow speed, and in parallel for High speed. It is the standard Citroen/PSA arrangement, and works well.

The radiator frame up front is designed to accept a single fan (placed centrally, or to one side with a blanking sheet), or twin fans. A fairly easy addition.
Chris

krekov
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Re: '89 BX 16V overheating on standstill?

Post by krekov »

RobC wrote:
Fri Jun 25, 2021 8:05 pm
They do run hot yes. Do you know the condition of the water pump? Fit another fan if you can. Perhaps also swop the warning switch on the block for the one that triggers the initial orange light on lower model BXs, then you’ll get a more timely warning in case of actual overheating.

What’s your oil temp gauge saying? I’ve found some oils run hotter than others. I stick with Total Quartz 10w 40 (as originally specced) and that seems to keep the oil temp lower than other oils, which all helps.
I used Total Quartz 9000 5W40. The oil temp stays within 100C, even in heavy traffic at 30C outside. Easily goes back to 80 after a while of normal driving.

I frankly don't know how the water pump's doing, the car had a timing belt change in 2007, 3 years before it was stored (it did not gain a lot of mileage before being retired), so I haven't changed it, only the timing belt itself. I assumed it was all good, since it didn't and still doesn't make any racket and there are no leaks.

The radiator doesn't look that bad, it doesn't leak and I flushed it thoroughly until no bits were coming out. But it could be there's some big hardened chunks that just won't flush out. It probably sat with the same coolant for 10 years until I bought it.
white exec wrote:
Fri Jun 25, 2021 8:51 pm
Is the half speed (via its dropper resistor) reasonably brisk, or a lazy draught?

Maybe check the actual engine temp with a non-contact (infra-red) thermometer, aimed at the thermostat housing (water outlet).
The half speed fan is pretty good, I even mistook it for full speed once. I did get a cheap Chinese thermometer to check the temp (it has about 5C of error) and at 110 on the gauge the thermostat housing was indeed around 110, something like 102, if I recall.
white exec wrote:
Fri Jun 25, 2021 8:51 pm
If you want to upgrade to twin fans, I have the circuit for operating them (from the existing thermo-switch). It uses 3 relays, working together, and no dropper resistance. Two fans operate (which must be of the same type) in series for Slow speed, and in parallel for High speed. It is the standard Citroen/PSA arrangement, and works well.

The radiator frame up front is designed to accept a single fan (placed centrally, or to one side with a blanking sheet), or twin fans. A fairly easy addition.
I would be very thankful for a diagram or explanation! The radiator, even if it was new, is not impressive at all for an engine this size and I'd like to have better thermal protection.

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white exec
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Re: '89 BX 16V overheating on standstill?

Post by white exec »

That sounds like you have done some good checks on the system.
I think upgrading to twin fans, and likely the full-width radiator, would be the best way to go.
Could he that someone here will have a pair for sale.
I'll post the circuit for you.

Our engines do not like overheating (more so the diesels), so keeping good coolant and proper cooling is important.

Wonder if your car has had either an engine change, or someone has transplanted some of the parts?
If you can post your VIN number, we can look to see what the car had when it left the factory.
Chris

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white exec
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Re: '89 BX 16V overheating on standstill?

Post by white exec »

The twin fans fitted to the BX 16v (16S) were pt.no. 95 593 547, and not to any other BX.
Parts lists them as also fitted to several C15 models:
BX 16S cooling fans 95 593 547.JPG
This may help find a pair. Best place to start is here.

The pair of fans must be of the same type and wattage. Not sure what the wattage is - could be anything between 190 and 310W, likely around 200.
Doesn't matter, so long as they're the same, and will physically fit.
(If a non-matching pair is fitted, there is a risk of odd running, and of audible "beating" as the two will operate at different speeds.)

The fans always operate together, never as a single.
Slow speed = fans in series
Fast speed = fans in parallel

Automatic switching is provided by the thermo-switch. Lo speed cuts in first, followed by Hi speed (as well).

This is the circuit for that. It was done in the '90s, specifically for a diesel BX19D that was going to do lots of caravan towing:
.
Cooling fan circuit-001 - second scan.jpg
The 3 relays are standard automotive types (30A or 40A). If all three are changeover type (5-pin) their positioning doesn't matter.
An optional additional relay can be used to bring in slow speed, where A/C is fitted (although BX models with A/C usually had twin fans anyway).
An optional dash rotary switch allows manual switching on of the fans, or left in Automatic mode (control by the thermo-switch).
Optional dash LEDs (or indicators) can show when Lo or Hi speed is operating.

The bank of 3 relays can be tidily housed in an ABS instrument box, or else engine bay mounted.

A similar system was used on the twin-fan Citroen Visa, but for some reason Lo speed was directly switched by the thermo-switch, with relays being used to change to Hi speed. A bit of a mish-mash. Doing everything via relays takes the electrical strain off the thermo-switch contacts, which has to be a good thing.

Make sure you use adequate wiring (2.5mm² stranded) for the main fan connections (shown as heavy lines). Other wiring can be light duty.
Chris

krekov
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Re: '89 BX 16V overheating on standstill?

Post by krekov »

Thanks for the diagram.
I got this car with a spare engine. The owner said he bought it after getting the car, but I can't be sure if it hasn't been changed. I'll post the VIN later today.
I don't think it's likely, as everything is original and looks exactly as it should in a 16v. Down to all the relays being colorful factory ones. The emblems are all present too.
The radiator is the correct one.

You mentioned a full width radiator, is there a thicker radiator that can be swapped in easily?

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white exec
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Re: '89 BX 16V overheating on standstill?

Post by white exec »

I'll try to check out the 16v radiator dimensions later today.
Most were the same thickness, just different widths, from memory. Will check.
Chris

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Re: '89 BX 16V overheating on standstill?

Post by RobC »

My first 16v came with just one fan. It was standard like this, at least in the U.K., for cars without A/C or tow bars.

If all is standard, the rad you have will be the same size, and there will be space in the housing to fit the other fan alongside.
1991 Citroen BX 16v

krekov
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Re: '89 BX 16V overheating on standstill?

Post by krekov »

Yes, there is space for a 2nd fan and I got one included in the parts that came with the car. I will attempt to install it using exec's circuit.

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Re: '89 BX 16V overheating on standstill?

Post by Kaapelimies »

Being a one fan model, I would suggest your dropper resistor has blown, so that the lower speed doesn't work. You can just replace it with a jumper wire so the fan will allways run full speed. If it's original, the resistor is an aluminium cylinder just behind the bumper on driv... no, your passengers side between lamp and radiator :) .
BX 4x4 estate, several BX Van's and some more normal estates in Finland.