Apparent Coolant Loss - 1.9d

[Ratty]

Hello all,

 

I am in a bit of a quandary concerning the coolant in my ZX 1.9D (not turbo), veteran 133K.

 

When I first acquired the car the coolant level in the expansion tank was on the Min mark (cold). Knowing the previous owner this did not in the least suprise me. I topped it up to the Max mark with water (having no anti-freeze to hand) for the 250 mile journey home. By the time I arrived home the coolant was fairly close to the Min mark (cold) again.

 

I then drained and refilled the coolant system. The coolant always seems to be slowly going down but never falls below the Min mark (cold). Having said that I tend to top it up again when it gets that low so it is difficult to say. I have only covered approx 250 miles since refilling the system. Most of the car usage has been short urban runs with one 70 mile run.

The cooling function appears to be working fine. The engine is generally running with the temp gauge at approx 3/8 of full deflection and the fans are kicking in at about 5/8.

 

I cannot see any hose or radiator leaks and am concerned that I have the beginnings of a head gasket failure. However the exhaust runs clear and there is no evidence of oil in the coolant or vice-versa.

 

In order to check this I went bubble-spotting in the expansion tank. I topped up the expansion tank to Max (cold), left off the radiator cap and fired up the engine, runnikng it at a fast idle.

- Initially no bubbles were seen.

- After approx 1 min a flurry of bubbles appeared flowing from the direction of the radiator. No exhaust smell noticed. My heart hit my boots.

- After approx 45 secs this flurry of bubbles stopped.

- Ran the engine at fast idle for a further 2 mins, no further bubbles seen.

 

As far as my limited knowledge goes there are three possible situations:

 

- This is the normal operating situation for this car, I am losing the coolant as the result of expansion from the radiator, which is then resettling lower after having cooled. The small flurry of bubbles is the result of some air in the system following the recent refilling.

 

- I have a small leak which I cannot see. This is causing the loss of the coolant and the flurry of bubbles is the purging of air which has entered the system via the leak.

 

- My head gasket is on the way out but is insufficiently advanced to give a constant stream of bubbles in the expansion tank (which I understand to be a common symptom)

 

Please could you advise me on which situation is most likely from the given evidence and of any other tests I might run to determine this. Clearly one of the above situations is the WRONG ANSWER.

 

Many Thanks,

Ratty

[Johndouglas]

From one month end to the other, you shouldn't need to put any water in the header tank. Are there any signs of leakage from the water pump or matrix. To confirm a leaking head gasket you could get a pressure test done.

[Ratty]

Thanks for the suggestion I guess I will probably need to get a professional to look at this, but in themeantime:

 

OK,

 

Further to my previous tests I have done much the same thing again, this time running the engine at 2500-3000 revs for a minute or so (not entirely from cold).

 

This time no bubbles appeared for over a minute then suddenly the coolant started expanding up to the top of the expansion tank and was full of tiny bubbles and steaming. I promptly turned the motor off, the level remained the same and the coolant continued to bubble and steam for a while. The Temp gauge was at 70 degrees at this point.

 

Is this a symptom of HGF and the time lag in it's appearance merely the time taken for the coolant ot circulate in the system or is this merely the coolant starting to boil in its unpressurised state (i.e. expansion tankcap off)?

 

Any thoughts or advice gratefully received,

 

Thanks,

Ratty

[Johndouglas]

It sounds as though you've got a blown gasket. Are there any water droplets on the dipstick? Or any white smoke from the exhaust? Often the engine oil looks milky.

[Ratty]

It sounds as though you've got a blown gasket. Are there any water droplets on the dipstick? Or any white smoke from the exhaust? Often the engine oil looks milky.

 

 

No other symptoms have been evident. The oil looks fine and the exhaust is uncannily clear given the mileage, no smoke at all, black, white, brown or blue.

[Guest Colin Hunter]

If the engine is running OK at present and the water loss is manageable, I would be inclined to leave things alone until there is some kind of developement in the situation. There is no point in changing a head gasket unless you are SURE it has failed. The bubbling/steaming/expansion you have noticed is probably just the thermostat opening and diverting the coolant through the rad, exactly as it should.

 

Another, quite common, source of coolant loss on the XUD is the plastic moulding which forms the back part of the water pump. This can become brittle and develop cracks over time and begin leaking. It could also draw air into the system when the engine is cold. This same thing actually happened on my sons 1.4 TU engined car which has a similar arrangement.

 

Best bet would be to get a pressure tester and give it the works with the engine cold. They couple up to the expansion tank cap and a hand pump is used to pressurise the system, usually up to about 15 psi. Do it with the system cold as leaks can sometimes "Take up" with expansion when the system is hot.

 

If you can't see any signs of external leakage, THEN suspect the head gasket.

 

Cheers. Hope this helps :unsure:

[Ratty]

Many thanks John and Colin for your replies.

 

I am starting to hope that I have raised a false alarm here. I have now run the car for a further 800 miles with the heater cranked all the way to blue and lost only a smidge of coolant in the process. This amount of loss differs so widely from the amount lost on the previous 250 miles (during which the heater and blower were extensively used) that I am strongly suspecting the heater matrix for the coolant loss. Colin's interpretation of what was observed when I checked the coolant for bubbles reassures me in this.

 

From what I read other symptoms of leaking heater matrix are wet passenger footwell & poor demisting capabilities. Whilst the first symptom was confounded by a leaking door (coming in via the speaker, no less) which has since been fixed, the de-misting is certainly less than efficient.

 

The idea of pouring goo into the coolant system seems a little counter-intuitive to me so I am tempted to stay clear of the Radweld option. Over the next few days I shall try to tear down the dashboard and have a look at the matrix. From what I understand this is a lengthy but not too technical task. Are there any unexpected nasties involved?

 

Cheers,

Ratty

[Ratty]

Addendum to the previous post,

 

I have rolled around in the footwells and read up the heater matrix removal in Haynes and clearly there is no easy inspection to be made. Baulking at the full 'first strip car to an empty husk' job merely to confirm my suspicions I am going to do a few trial runs with the heaters on and closely monitor the coolant levels. Stay tuned for the next rivetting instalment.

[Guest Colin Hunter]

If You suspect the heater matrix this is the right ime of year to bypass it. Cut the 2 hoses that go to the matrix and join them together with a bit of pipe and 2 jubillee clips. If the water loss stops you've cracked it. You can re-connect the hoses in the same manner once you have replaced the matrix.

 

Cheers. Hope this helps. :)

[Ratty]

Righty,

 

Just to add a bit of closure to this thread.

 

SInce the initial identification of the problem I have driven approx 3,000 miles, 95% of it on the motorway. In this time the coolant level in the expansion tank has fallen 10-20 mm.

Only on one journey did I use the heater.

 

It appears that this amount of coolant loss is manageable. I believe that the initial huge loss of coolant is probably due to incomplete bleeding of the coolant system following a coolant change. This in turn I blame on Citroen's whacky top-up tank coolant filling design and my own inattention and ineptitude is in no way at fault.

 

I still intend to run a control journey of 100miles or so with the heater on to see if this makes any difference.

 

Colin, thanks for your suggestion. I have baulked at the prospect of playing Sweeney Todd with the heater feed but if I do experience a major loss when I run the above mentioned test I may well have to resort to it before we run out of 'summer'.

 

Cheers all.

[Guest Colin Hunter]

Hi Ratty.

 

I have to agree that the coolant expansion arrangement leaves a lot to be desired. It is the product of having a relatively low bonnet line with a tall(ish) engine, producing a situation where it's difficult to provide a proper "header" tank and a self bleeding system. The temporary header tank arrangement works pretty well though, and allows you to get rid of the air in the system pretty well. The bubbling/steaming you have seen may well be the remaining air coming out when the stat opens.

 

Also, water at ambient temperature contains dissolved gases which are released upon heating to boiling point, Boiling the water in a kettle will get rid of this as well as most of the hardness salts (Calcium carbonate etc) in the kettle, rather than in the engine. It's a good idea, especially in a hard water area, to boil all the water you use in your engine to remove these potentially harmful salts before mixing with anti-freeze and adding the mixture.

 

I think it's now fairly safe to assume that you don't have a problem with coolant loss. If the heater matrix was leaking you would definitely know by now. A drop of 10-20 mm is very little and may well be down to the release of these disolved gases from the water.

 

Cheers. Hope this helps explain things. ;)