BX diesel auto overheating

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detheridge
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BX diesel auto overheating

Post by detheridge »

Hi folks,
my wife's BX diesel auto (J reg) is regularly coming up with the over heating warning lights. Now our local indie Citroen garage tells me that one reason might be that it's only fitted with a single radiator fan, and that Cit recalled some of them for retrofitting with twin fans as this was a problem. Does anyone know more on this.
Ironically enough, we stripped the bits off her previous BX diesel auto (K reg) and that one too had a single fan!
If adding another fan doesn't cure the problem, the garage suspects it might be a head gasket.........

Best wishes,

David.
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DavidRutherford
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Re: BX diesel auto overheating

Post by DavidRutherford »

detheridge wrote:Hi folks,
my wife's BX diesel auto (J reg) is regularly coming up with the over heating warning lights.
When? On the open road? in town? going up hills?
detheridge wrote: Now our local indie Citroen garage tells me that one reason might be that it's only fitted with a single radiator fan, and that Cit recalled some of them for retrofitting with twin fans as this was a problem.
That depends. Does the fan come on a lot? It should come on only when you've been sat parked (in traffic) or moving at very low speeds (under 10mph) If it comes on on the open road, then yes there is something else wrong.

Also... it was fine before, so something has changed to make this happen. It's highly unlikely to have lasted since 1991 if it needed two fans.

Before you condemn the head gasket, I'd be looking for things like a silted up radiator or similar.
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detheridge
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Re: BX diesel auto overheating

Post by detheridge »

DavidRutherford wrote:
detheridge wrote:Hi folks,
my wife's BX diesel auto (J reg) is regularly coming up with the over heating warning lights.
When? On the open road? in town? going up hills?
Hi David,
it happens on long hills and going along the motorway at 70 and a bit.
detheridge wrote: Now our local indie Citroen garage tells me that one reason might be that it's only fitted with a single radiator fan, and that Cit recalled some of them for retrofitting with twin fans as this was a problem.
That depends. Does the fan come on a lot? It should come on only when you've been sat parked (in traffic) or moving at very low speeds (under 10mph) If it comes on on the open road, then yes there is something else wrong.
Now my local Cit folks say that you should be able to leave it running all day without it over heating. When they had it in for some work recently, just leaving it on tickover had it boiling up!
Also... it was fine before, so something has changed to make this happen. It's highly unlikely to have lasted since 1991 if it needed two fans.

Before you condemn the head gasket, I'd be looking for things like a silted up radiator or similar.
Great! I'll ask them to check and get back to you.

Many thanks,

David.
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DLM
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Post by DLM »

Firstly, the bad news. If you look at the "Car Mechanics" BX buying guide from 1998 I added to the BX Blog review spot recently, you'll see some fairly accurate comments about the temperature warning lights. In short, the rule is along the lines of:

1. If the orange warning light comes on and stays on , you're almost certainly in head gasket-job territory.

2. If the red light comes on it's definitely head gasket time.

Sorry - but this is the brutal truth. For comments about fitting a second fan, see the end of this post.

The only exceptions to the above are where the orange light comes on dimly for a short time under certain circumstances like high speed, a very steep incline, etc. Here there could be a problem of restricted flow in the cooling system, e.g. half-opened thermostat, silted-up radiator (cold-spots on the radiator are a giveaway), water pump on the way out, low coolant level due to a slow leak.

If this latter description fits the symptoms, methodical diagnosis and remedial action may prove effective (e.g. thermostat examination and possible replacement, radiator flushing or replacement, general flushing-out of the coolant system).

A simple test will tell if there is far-advanced head-gasket damage: Start the the car from cold, whip off the radiator cap, and stand back. If there's a fountain of foaming rusty gunge within a few seconds, then your head gasket has definitely blown. Before this happens, you may well find that the coolant system is over-pressuring: suspect this if the top hose remains rock-hard even if the engine has cooled down overnight, and if removing the rad cap in these circumstances causes pressure to be released.

When it comes to serious remedial action for overheating, the best thing to do is to look for the underlying cause.

1. When was the coolant last changed? What's its colour and is it rusty?
2. Are there any cool spots on the radiator?
3. Is the thermostat opening properly?
4. Is the coolant level low?
5. Does the existing fan come on - are the contacts on the switch clean? Does the fan work if the contacts are bridged?

As for the two-fans issue, I'll check my copy of the Diesel BX Revue Technique as it's good on things like that, but my belief is that the 2-fan system (an official Citroen retro-fit kit) was only recommended for cars which consistently towed heavy loads. I once owned a 19TGD with the 2-fan kit fitted (which didn't stop the car from needing a head gasket soon after I bought it). I also know of someone who's run 3 BX19Ds which tow caravans and other heavy loads for a business. None have had the 2-fan conversion, and only one has ever overheated (slow leak from bottom hose). One was a BX auto.

Your garage may be suggesting you fit a second fan because they know it's an old car and that the coolant flow does become restricted over time. A second cooling fan may alleviate the problem, but it's only likely to be a live-with-it holding action rather than a remedy.
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Post by DLM »

David posted and you replied while I was writing the comments above. He asked the most pertinent questions. Looks like a restricted coolant flow problem.

Get the cooling system and radiator flushed, replace the thermostat if necessary. Replace the coolant (bled properly on refill by someone who knows how to do this on an XUD engine - very important ), then drive again and observe.
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Re: BX diesel auto overheating

Post by DavidRutherford »

detheridge wrote: going along the motorway at 70 and a bit.
In which case you could add 8 fans and it would make no difference at all. Radiator cooling fans have little effect over about 30mph, and are completely useless above 40mph. They are there ONLY to provide airflow over the rad when the car isn't moving forwards fast enough. (like towing a big caravan up a long hill at 30mph, at full power.)

Another test for head-gasket failure:

First thing in the morning, remove the rad cap and then replace (to remove any residual pressure)
Start the engine and allow it to run for about 30 seconds. Stop the engine.
Now remove the rad cap again. Is there any release of pressure? If so, the HG is goosed. There should be no pressure build up at all in that first 30 seconds of engine running.
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Post by ken newbold »

We only have one fan on our BX diesel auto. But there does seem to be a case history of HG failure on these cars.

Don't overlook the obvious first. Check the radiator and the thermostat.
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Post by tom »

If it has lasted without manifesting this fault for this long, it will have been used in much hotter temperatures than this. THe cooling system at this age can cause all sorts of problems.The radiator can be shot, that could well take the Head gasket with it. I would certainly use David's test before drawing any conclusins but if it turns out not to be the HG, budget for a cooling system rebuild anyway. Pump, Radiator, any hoses you can get, a thermostat , A fan switch and a filler cap. BXs live or die by their cooling systems.
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