I need to change a head gasket on a BX GT

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

adamskibx
Posts: 250
Joined: 29 Nov 2004, 02:46

I need to change a head gasket on a BX GT

Post by adamskibx » 13 Nov 2005, 18:02

Hello. Ive just picked up a MK1 BX that I have replaced my estate with. The only thing I know needs doing is the head gasket. Its the 1905cc 1985 105 BHP engine and I have all the parts I need including the head gasket. I just wanted to see if anyone has got any advice on doing this job as I did a search and only found info on the diesel cars really. The car can only run for about 5-10 minutes before a warning lamp comes on on the dash, but the engine sounds very sweat so is worth repairing-Its also only done 43,000 miles. Oil is mixed with water and vice versa-making the oil level way too high! Basically, I dont want to cook the new gasket when put together again and im not convinced the fan is coming on. My plan is to do the gasket and timing belt, service the cooling system with a flush etc and check all fan electrics and if necessary install a short term bypass switch to manually turn it on. Aparently the reason for the failure was a jammed thermostat meaning the water didnt go round the rad but this is now fixed. Does anyone have any advice or tips about what I should do when etc in order to give me a fighting chance of saving this engine?

This is the car im talking about: http://cgi.ebay.co.uk/CITROEN-BX-GT-NOT ... dZViewItem

Apart from the head gasket the car is superb. Only rust on the body is the bit on bottom of drivers door and the suspension is the smoothest BX suspension I have ever experienced- Thought they'd toughen it up for the GT but its way way softer that the BX TGD I just sold.

Regards, Adam

Stewart(oily)
Posts: 842
Joined: 07 Oct 2005, 16:31
x 13

I need to change a head gasket on a BX GT

Post by Stewart(oily) » 13 Nov 2005, 20:10

The main difference is that the engine is a "Wet liner" engine, read the BOL and look at the section on using bolts and bits of timber to hold the liners in place whilst the head is off, when I did my GTI I just turned the motor to the indexing position before I started the job and did not rotate the crankshaft at all, be warned though if the crank moves at all the liner seals will be damaged and then the whole thing has to come out :evil:
Good luck
Stewart

Stinkwheel
Posts: 558
Joined: 28 May 2004, 01:02
x 1

I need to change a head gasket on a BX GT

Post by Stinkwheel » 13 Nov 2005, 20:30

OOhhhhh

that takes me back, My mum had one just like that when i was 17, same colour and everything. I learnt to drive in it.

Nice one Adam,
Wanna CX prestige to keep it company :-)

adamskibx
Posts: 250
Joined: 29 Nov 2004, 02:46

I need to change a head gasket on a BX GT

Post by adamskibx » 14 Nov 2005, 00:52

Cheers Stuart:- Thanks for that advice:- Yeah I read about the fact that its a wet liner engine and read the manual on the job- It says to use large washers on bolts to keep the liners in place but I thought that the only time the liners could be disturbed is when the head is coming off or going back on again, during which time you could not have those bolts or wood or whatever there anyway. My plan is to use exactly 10mm drill bits as the locking device for the camshaft and crankshaft and to make sure the liners arent distubed in any other way; ie keeping the engine locked and not knocking the liners or anything at all until the head is bolted up again.

Matt: I thought you sold that CX Prestige?? This BX will keep me busy enough I feel thankyou:-) yeah it really is a classic machine- Its super smooth, its got the best Citroen dash ever, lovely seats, 4 electric windows, fuel computer, and an original 4 speaker radio cassette! Its the best car ive ever owned even though I cant even use it yet:-) Im going to be busy trying to get this head gasket sorted and failing that ill bolt a GTi engine in from a scrappy.

Regards, Adam

User avatar
fastandfurryous
Posts: 1384
Joined: 07 Jul 2004, 17:57
x 3

I need to change a head gasket on a BX GT

Post by fastandfurryous » 14 Nov 2005, 02:08

Adamski... I don't know if it would be of any help to you, but I may well shortly have a 1985 BX GT engine spare that you would be welcome to. It's from the GT "DIGIT", as it needs a new carburettor (it's knackered) and I don't like petrol engines, so I'm probably going to TD convert it.

With the carb from your engine, it would be a great engine. Oil and coolant are clean, No head gasket problems.

Any use to you?

adamskibx
Posts: 250
Joined: 29 Nov 2004, 02:46

I need to change a head gasket on a BX GT

Post by adamskibx » 14 Nov 2005, 20:45

Hi fastandfurios.

That engine may very well be very useful to me in the short term if this gasket change isnt successful, and even if it is I will definaly be interested in it as a spare engine in case my repairs dont last too long. Ive investigated the engine so far but havent done anything drastic yet- The water level drops very quickly, meaning the oiL level is getting stupidly high (only ran for 4 minutes), and the idle speed seems to be about 2000 RPM for some reason but I expect the head gasket has something to do with that. :? Also, even with the water topped up, I cant see any water coming out of the thermostat housing when its running and so the radiator is not getting hot water-having said that, when I undid the filler cap on the rad when it had run for 5 minutes, water gushed out and it was hot. I have placed the thermostat into boiling water and it opened up as it should so that works. Im concerned the water pump has gone as well as the head gasket and that the problem with the thermostat never existed- Ie its easier to sell a car saying the thermostat went and has now been replaced rather than saying that it was the water pump that caused the gasket problem. He seemed like a nice guy but I just find it a bit odd that the thermostat was replaced even though they knew the head gasket had gone. Well, basically im going to do the head gasket, refill and bleed the cooling system, disconnect the hose to the radiator and if no water comes out, then ill have to take things apart again and fit a new water pump. Or would it be a better idea to replace the water pump anyway? I think the safest way to do it without spending the money on a new water pump if its not necessary would be to remove the thermostat completely and see if water gets pumped out before the engine get too hot. :roll:

Thanks again for your offer of the engine- I will almost certainly take you up on that- Just let me know when you have done the engine swap etc....
and good luck with it too! Incidentally, how easy is it to change to a different engine with regards to electics etc? Also, how have you found the GT engine fuel and performance wise? Im hoping to get this engine MOT ready in two days and then fine tune it all afterwards.

Id like to know more about your car- The most shocking thing about the one I got is the sound quality of the original cassette/radio- Its amazing; in fact its the best in car sound sytem ive ever experienced.

Regards, Adam

RichardW
Forum Treasurer
Posts: 8920
Joined: 07 Aug 2002, 17:12
x 315

I need to change a head gasket on a BX GT

Post by RichardW » 15 Nov 2005, 09:48

Adam,

"The water level drops very quickly, meaning the oiL level is getting stupidly high (only ran for 4 minutes), "

Seems a bit odd, as normally the oil is at higher pressure than the water, but I guess if it's bad, the head may be warped at the oil return gallery end. It's going to need skimming anyway. I think the fact that the water is getting into the oil indicates that the water pump is OK, and generating pressure, but I'd be inclined to change it anyway.

Errrr..... here's another thought.... has someone already had a go at the head, and disturbed one (or more) of the liners, breaking the bottom seal??? Don't know how you'd check though - pour water down the water jacket once the head is off, and see if it comes out the bottom of the liners maybe? Perhaps you should pull the engine out - it will make getting the head off a sinch, and if you need further engine rebuilding (eg new liner seals!) you will have to take out what's left anyway.

RichardW
Forum Treasurer
Posts: 8920
Joined: 07 Aug 2002, 17:12
x 315

I need to change a head gasket on a BX GT

Post by RichardW » 15 Nov 2005, 15:21

Have you got access to a coolant pressure tester - or could you make one? Perhaps you could drop the sump, then pressurise up the cooling system, and see if it leaks out between the liners and the block - you should be able to work out where the join is from underneath. At least then you will know what you are in for...

I'd start a thread on bxclub - a couple of them have got engine cranes they feel are underused :wink:

Paul Mi16
Posts: 64
Joined: 15 Nov 2005, 19:23

I need to change a head gasket on a BX GT

Post by Paul Mi16 » 15 Nov 2005, 19:42

I would suggest a compression test first before stripping the engine. By the time you have had the head skimmed and bought all the parts it could be as a cheap and easier to swap the engine, especially if the donor engine is known to be good.

Paul.

adamskibx
Posts: 250
Joined: 29 Nov 2004, 02:46

I need to change a head gasket on a BX GT

Post by adamskibx » 19 Nov 2005, 21:34

Hello- Right, ive changed the head gasket but need to do it again-this time ill get the blimmin thing skimmed. A waste of time doing it without doing this in the first place I know, but one learns from the mistake. Also, apart from the head gasket problem, a new problem developed since changing it. The car started up but idles way too low-in fact if you dont keep a bit of gas on it will stall- every now and then it backfires through the carb so id imagine the valve clearances need changing. My question is: where do you get the shims from? I can easily check the valve timing but there is no reason why this should be out as the belt is on in the same position and the dowl holes will tell me if it is wrong. Basically it appears as though I have to check the valve clearance against what it should be, then measure the current shims with a micrometer, then calculate the size of shim I have to order- I suppose the only reason why the clearances would be out is if the head has been compressed or decrompressed in relation to what it was with the old head bolts and gasket on? Thats the only reason I can see as the valves are all preset and built into the head. Having said that, the compression of the engine seems good as you can tell by turnig the front roadwheel with and without the plugs in that there is a massive difference in force needed so the valves are obviously sealing. It also stiffens up equally 4 times per revolution of the camshaft-not very scientific I know but its the best I can do without a compression tester. This leads me to beleive it may be the ignition timing instead, but surely that is fixed in the head too and shouldlt have changed? My current plan is to dismantle it all again, then as already suggested, pour water into the jackets around the liner seals and see if anything comes out the sump, and , if not, then ill get the head skimmed if it is good enough to do so and fifit it all again then give the whole thig a good service etc in terms of valve clearances and ignition timing. At the moment, there is a lot of steam in the emmisions and a bit of bubbling in the water system when running. Cheers, Adam

citronut
Posts: 10938
Joined: 29 Apr 2005, 00:46
x 3

I need to change a head gasket on a BX GT

Post by citronut » 19 Nov 2005, 22:29

it only needs re shiming if you have cut the valve seats or hevaly laped them in,if you have not done any of this the valve clearances will be the same as when you took it apart
regards malcolm

adamskibx
Posts: 250
Joined: 29 Nov 2004, 02:46

I need to change a head gasket on a BX GT

Post by adamskibx » 20 Nov 2005, 18:52

Oh OK cheers Malcom- I must have got the belt a tooth out then as its not right if its backfiring through the carb. Ill check to see if the alignment holes line up on the crankshaft and camshaft pullys (hopefully they wont then ill know what needs doing). Its just that this engine is normally a spritely engine that revs up quickly to a small touch of the throttle and at the moment its struggling to idle and when I floor it, the revs just creep up like an extremely underpowered diesel engine would. I certainly wouldnt feel safe pulling out of a junction with it:-) Thats how severe it is.

Cheers for all help. Adam

Paul Mi16
Posts: 64
Joined: 15 Nov 2005, 19:23

I need to change a head gasket on a BX GT

Post by Paul Mi16 » 20 Nov 2005, 20:19

Its sounds like belt timing could be wrong, an engine that is unwilling to rev might be the timing is retarded. Have you removed or altered the distributer when you took the head off?

I've known belts with timing marks on them be wrong, so its best to line up all the marks on the pulleys amd use the pins to lock them in place.

Paul.

micitroen
Posts: 93
Joined: 17 Aug 2005, 01:48

H/gasket.

Post by micitroen » 20 Nov 2005, 20:48

Could be as Paul says, if you've taken off the dizzy and replaced it a bit out it could cause the probs you've got with regard to the timing.....I only know this as I've done it myself ......not with a Citroen.....with a 760 Volvo. As you have described, it starts ok but revs really lethargically.....can't remember exactly now, but the plug leads were all about 2 holes out (the 760 is a 6 cylinder) when I'd sussed it and sorted it out it was fine. If its only a little out, try loosening the lock nut on the dist shaft and turning the head of the dist to see if it makes any difference .....as you say you still have to do the H/gasket again but at least you will have sorted this problem........thats always assuming the whole timing hasn't slipped.

adamskibx
Posts: 250
Joined: 29 Nov 2004, 02:46

I need to change a head gasket on a BX GT

Post by adamskibx » 21 Nov 2005, 22:48

Right well today I have taken the head off again to get it skimmed. Before I did that though I checked the valve timing. The hole in the crankshaft pully lined up with the recess behind it, as did the one in the camshaft pully and I wanted to check the valve clearances but found my feeler guages are not metric so just made sure I could fit a thin one through each gap when the cam in question was pointing upwards-no problem so they are all closing fine. I cant see how the ignition timing can be out as I havent touched the distributor at all but when I put it all back together again ill have a look if things are still the same. As for HT lead connections- I always thought if you got one or two the wrong way round it would sound extremly odd and be almost imposible to start? I didnt label them as they are in a black thing that keeps them in order and just took that off together with the distributor cap. However the Haynes is confusing here. It says "make sure you put the right HT lead on the right plug. The cylinder numbers are 1,3,4,2, number one cylinder being at the flywheel end of the engine". I just assumed thats an error as that would be the firing order, not the cylinder numbers, but I may be wrong? I assumed the cylinder numbers are 1,2,3,4, number one being at the flywheel end. Basically, due to the lengths of HT lead available, the only two lead plugs I could have got wrong are the middle two but I think its unlikely as you can tell by the way they are bent where they have been etc. I know somethings not right as when I got the car it would idle at 1500 RPM (lack of water due to HG prob making the auto choke think its cold when its not), but now you have to have some accelerator on to keep it above 1000, and its when you let it go down to 1000 that it spits and chokes through the carb until it stops.