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Mar 24, 2024 15:07:42 GMT
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I know the go to reply is gonna be head gasket, but hear me out...
So I've got an xud7 powered BX. I bought it with a split coolant hose caused by it touching the exhaust. I fixed that, bleed it up, noticed some bubbles in the header tank but everything else was fine so I decided its probably a bit of trapped air and I'll send it and see what happens. After a month of daily driving it with no issues at all the coolant over pressurises and blows coolant out of the cap. The thermostat was stuck shut so I replaced that, bled it up and once again bubbles in the header tank.
The engine runs spot on, no missing, fires up fine from cold, I've done a sniff test and cones back clear of combustion gases. A mate suggested it could be the water pump failing and sucking air in through the seal. It did have a funny noise from that area and the cam belt was sitting funny on the pulleys which could tye into that. Once off it was clear the WP bearings had failed, so replaced it all, bled it up and still a constant flow of bubbles in the header tank.
So before I pull the head is there anything I'm missing here that could cause this? There's no EGR on this engine, seems to be a very basic coolant system. It's just the fact theres no other symptoms of HG failure which I'd expect with this amount of bubbles coming through.
So to summarise
Lots of bubbles in header tank
Bubbles go away when revs held up
No misfiring
Starts fine even cold
No white smoke from exhaust (other than a bit of diesel smoke)
Engine runs sweet as a nut
Coolant system works fine. I've left it idling for near 3 hours solid with the cap on. Fan kicked in and out as it should, temp sat between about 84/87° with the fan kicking in/out. No over pressurising of the coolant system. Just a steady stream of bubbles at idle with the cap off.
Any suggestions greatly appreciated 👍
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Mar 24, 2024 20:33:17 GMT
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I'd be inclined to just drive it normally and monitor it closely.
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stealthstylz
Club Retro Rides Member
Posts: 14,834
Club RR Member Number: 174
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Bubbles in header tankstealthstylz
@stealthstylz
Club Retro Rides Member 174
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Mar 24, 2024 21:00:25 GMT
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I would drive that but keep a couple of 5 litre bottles of water in the car just incase, and probably never need them
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fulvia1436
Club Retro Rides Member
Finally started a thread for my Fulvia life
Posts: 341 
Club RR Member Number: 63
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Bubbles in header tankfulvia1436
@fulvia1436
Club Retro Rides Member 63
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Mar 25, 2024 11:17:50 GMT
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Leakdown test will show you what's leaking, and where
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'59 Austin A40, '59 VW Beetle, '63 Mk1 Cortina, '57 Austin Gypsy, '68 Fiat 850 Coupe, '68 Alfa Duetto Spider, '72 Lancia Fulvia 1.3S, '73 Lancia 2000 Sedan ie., '72 Lancia 2000 Sedan, '67 Lancia Fulvia 1.3, '83 VW Passat GL5 Estate, '81 Volvo 245 Estate, '85 Lancia Thema 8V Turbo Estate, '99 Lancia Kappa 20V Turbo Estate, '00 VW Sharan VR6, '06 Fiat Multipla 1.9 JTD, '10 Fiat Multipla 1.9 JTD, '66 Lancia Fulvia 1.3
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andyborris
Posted a lot
Freedom is just another word for nothing left to lose.
Posts: 2,158
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Mar 25, 2024 13:28:05 GMT
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Could the bubbles be caused by the agitation of the pumped flow hitting the header tank?
If there's no overheating or no water loss, I'd just carry some water and make sure the recovery service was up to date.
It's an old BX, even a perfect one should carry the above! Great cars though, loved mine.
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Mar 25, 2024 17:21:06 GMT
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Bubbles in your header tank could mean the coolant is boiling probably by restricted flow around the cylinder furthest from the radiator, head gasket passages blocked etc. I bet if you drove it very hard in hot weather it would boil over. Until then enjoy driving it.
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Mar 25, 2024 18:02:47 GMT
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Bubbles in your header tank could mean the coolant is boiling probably by restricted flow around the cylinder furthest from the radiator, head gasket passages blocked etc. I bet if you drove it very hard in hot weather it would boil over. Until then enjoy driving it. If that was the case it would take a minute or so for the bubbles to appear from cold. That isn't the case tho, they are there as soon as it fires up. They also go away when the revs are held and stay gone for a short time after it returns to idle. Give me a min and I'll make another post with some videos in I made today showing what's going on |
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Mar 25, 2024 18:14:53 GMT
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Bit of an update post with some videos for reference So this is what's going on in the header tank. Lots of bubbles at idle, hold the revs up and they go away, once it drops back to idle it takes a little while for them to appear again I redid the combustion test and again it came back clear And then I used the test on the exhaust to confirm it was working Again it's been sat idling for over an hour with no issues whatsoever. Coolant system has pressurised with the cap on, but not over pressurising. Fans kicking in fine and the temp is sitting nicely. No sign of any Coolant leaks at all.  All I can think is something (maybe a hose) isn't quite sealing right but is sitting in a way that for some reason is only allowing it to suck air in and not let Coolant out. Once the coolant system is pressurised it won't let it suck any air in. If that is the case it's not something I've seen before but I guess it's not impossible. I'll run it and see what happens. I'll update this thread if I ever get to the bottom of it in case it helps anyone else in the future |
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andyborris
Posted a lot
Freedom is just another word for nothing left to lose.
Posts: 2,158
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Mar 25, 2024 22:25:54 GMT
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You do know that all RHD French cars are just revenge for Waterloo and since the 1980's it's been psychological, rather than direct action?
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ChasR
RR Helper
motivation
Posts: 10,192
Club RR Member Number: 170
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Bubbles in header tankChasR
@chasr
Club Retro Rides Member 170
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Has the system ever been flushed out? I've seen this before, but only when someone put screenwash into the header tank (no, really).
The other thing is, how good are the heaters? If the BX is like 205, 106s an 306s, they really do need to be bled properly, so as to remove airlocks. The biggest giveaway tends to be a poor heating system.
Best way to do it on a 106 and 306 is to brim the coolant right to the neck of the header tank, with the car facing nose up on an incline. Then hit the bleed points as follows:
-Thermostat (an allen head screw)
-Heater matrix (tends to be a thumb screw)
-Sometimes the rad has one, but that tends to be BMWs IME.
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ChasR
RR Helper
motivation
Posts: 10,192
Club RR Member Number: 170
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Bubbles in header tankChasR
@chasr
Club Retro Rides Member 170
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Leakdown test will show you what's leaking, and where I'd second this. |
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Mar 26, 2024 15:47:43 GMT
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You do know that all RHD French cars are just revenge for Waterloo and since the 1980's it's been psychological, rather than direct action? I'm quickly starting to realise this 🤣 |
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Mar 26, 2024 16:02:22 GMT
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Has the system ever been flushed out? I've seen this before, but only when someone put screenwash into the header tank (no, really). The other thing is, how good are the heaters? If the BX is like 205, 106s an 306s, they really do need to be bled properly, so as to remove airlocks. The biggest giveaway tends to be a poor heating system. Best way to do it on a 106 and 306 is to brim the coolant right to the neck of the header tank, with the car facing nose up on an incline. Then hit the bleed points as follows: -Thermostat (an allen head screw) -Heater matrix (tends to be a thumb screw) -Sometimes the rad has one, but that tends to be BMWs IME. Yeah I've dropped the coolant a couple of times (repairing a split hose and then when I replaced the stuck thermostat). The last time I did it I ran coolant flush through it beforehand and emptied the whole system when replacing the water pump at the weekend. It did seem like there was some sort of contamination originally because the coolant was getting very frothy. That problem seems to of died right down now since flushing it. There is evidence of some sort of rad weld in the coolant. The lad I bought it off said the head gasket was gone when he got it so he replaced it. I can't help but wonder if he had the same issue I'm having and couldn't fix it, wrongly thinking it was HG failure. The heaters are probably the best I've ever had in a car (granted most of my cars have been old sheds). They get hot and they do so quickly. I've bled the system at the thermostat and the rad bleed screws, I didn't realise there was one on the heater matrix so I'll have a look for that in a little 👍 |
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Mar 26, 2024 16:18:27 GMT
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I'm no expert on this but I'd be inclined to put the cap back on and forget about it. It looks more like some soap in the water than actual air bubbles being produced.
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Mar 26, 2024 22:05:53 GMT
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What he says ^^^^
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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