ZX Coolant mystery

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Andrew Robey
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ZX Coolant mystery

Post by Andrew Robey »

Some urgent help required here please, fellow ZX owners.
Inital symptom being investigated was a very sharp increase in engine temperature, and no hot air from the heater. Safe in the knowledge that I put a new matrix in a couple of months back, and having checked the coolant level about 2 weeks ago, I immediately assumed an air block could be the cause.
When I try to bleed the system, however, this happens:
Go through the motions: extra header tank in place, bleed first on the rad, then by the thermostat housing, and then at the matrix union, until lovely clear coolant coming out.
Start the engine and run, but the coolant is forced back into my header tank until it overflows, and air is present at all bleed point again.
Is there a valve which could have jammed or something else which might explain this? Where can the air be getting into the system?
[xx(]
Andrew Robey
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Post by Andrew Robey »

Hmmm - may have solved my own mystery.
Read an old thread which advised attaching a bottle to the rad overflow and see if any coolant coming out, ie: system being pressurised.
Sure enough within 20 seconds of engine running, a steady stream of liquid being expelled. Could this be anything EXCEPT head gasket (please...?!)
[:(]
oilyspanner
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Post by oilyspanner »

If you run the car without the radiator cap on do you get a steady stream of bubbles in the header tank? when you rev the engine do these bubbles increase? I think you know what may come next.
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Post by BonceChops »

Did all of the radiator get hot when the engine overheated?
Andrew Robey
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Post by Andrew Robey »

Not sure about how much of radiator was hot - didn't check.
Regarding air bubbles - I have only being running the engine on tickover, but when I attempted the first bleed, A LOT of big bubbles did come up, jacuzzi-style.
There is no sign of mayonaise on the dipstick and the coolant is clear, if this makes any difference (he asked hopefully..?), although there have only been about 6 miles done since first erratic temp.
oilyspanner
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Post by oilyspanner »

It will take a while for mayo to appear, bleed the engine fit the pressure cap and run the engine whilst squeezing the top hose, if you feel pulsing and the hose "pumps up" before engine is hot then its the gasket, you will also hace a never ending supply of bubbles from bleed points.
Stewart
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AndersDK
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Post by AndersDK »

The most sure check is as OilySpanner suggests above :
- air bubbles seen cap off at engine tickover.
If it is jacuzzi style bubbles - then the cylinder head has cracked with a gross fault.
It's not a common fault - but sh!t happens !
Engine oil will rarely be contaminated with coolant on these engines on HG failures.
Likewise it's not a rule to see traces of oil in the coolant - would even in most cases be present from greasing parts during repair/service work.
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Post by Andrew Robey »

Thanks all - time to price up a HG change then.[V]
A further point for general interest:
It had been bothering me why the fans had not been sucking small children off the pavement trying to cool the engine - it turns out the terminals in the temperature-sensitive fan switch are all corroded, presumably from being covered in coolant from the upper bleed point!! This will have exacerbated the situation no doubt.[}:)]
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Post by oilyspanner »

The fans only come on once a year anyway!
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rg
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Post by rg »

FWIW,
This "fans don't work because of corroded connectors/earth" situation damaged by 405 head as well.
It seems pretty common - I seem to hear of it so often with mature PSA products. Maybe a warning to us all to occasionally test the car and check that the fans cut in.
rg
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Post by James.UK »

RE non working fans, I found this modification to the elec wiring for peugeot diesel fans, it may be of interest to those of you who undestand it. [:I] http://images.google.com/imgres?imgurl= ... 8%26sa%3DN .... Any prizes for the longest URL on the planet? [:D] [:o)]
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Post by James.UK »

The subject of non working fans on the ZX made me think, (ouch) I have noticed that on my mates Astra, the fan can be heard running every time he parks up and exits his car (he parks his car next to mine) but I can't ever recall hearing my fans run? not ever! Sooo I put my car in the garage, and ran the engine for nearly an hour.. Temp went up to approx 110 (normally runs about 90 ish I.e. less than halfway up the gauge) but the fans did not start to run, rad was warm-hot from top to bottom, I put the heater on maximum and within secs the temp dropped back to normal..
I thought fans were supposed to run after the engine was turned off untill the engine had cooled off a bit? Outside temp today is around 14c 58f ish so surely the fans should have at least come on when the engine warmed up?
Am going to get the fans tested tomorrow to make sure they both work!
During the time I was messing under the bonnet I sprayed all the elec connections I could find with silicone spray. When I was spraying around the headlights my engine revs picked up briefly from 900 to about 1200? that happened both sides? Strange huh?
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AndersDK
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Post by AndersDK »

James -
The driving gas & solution in the silicone spraycan is highly flammable [:p]
Silicone keeps out water - but always a good idea to clean off sprayed items - before spraying.
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Post by James.UK »

Thanks Anders.. hmm interesting, I cleaned all the elecs I could find when I did the first silicone spray some two years ago, since then I just sort of top-up with more silicone, [:o)] as for flammable, hmmm I forgot that! [:I] If the wind was in the right direction bits of me might have landed locally to you? lmho... Spare bits are always handy, puts a whole new perspective on "an arm and a leg" huh...[:D]
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Post by RichardW »

James,
Bad news....
The fans should come on at around 95°C and quickly drop the temp back to 82/83. If the temp gauge was showing 110 something is wrong (fans should be trying to push the car out of the garage on high speed by that temp!). You say however that the rad was only 'warm' - it should have been too hot to touch at the inlet - possible thermostat problem or rad blocked? You can test the fans by pulling the connector off the switch on the radiator and shorting the pins out - I think shorting all 3 should give you high speed fans, shorting (the right!) two should give you low speed. If fans come on OK, then suspect the rad switch - you can take this out and test it in a pan of boiling water (not forgetting that you will lose part of the coolant!). Foregoing assumes Zx set up same as BX / Xantia.....
Oh, and try and avoid letting it get up to 110 again, as you headgasket is not likely to thank you for it!
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