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Up Topic C1 Information / Repairs - Faults & Fixes / My C1 overheating ( or not....)
- - By mac140 Date 09.08.19 10:56
Morning gents. My first posting, I hope this makes some sense.
I have a 2001 125 exec , it has been SORN for over a year and now it needs to go....It was laid up due to too tight valve clearances , so did not want to burn the valves. These have now been sorted and the bike started on the button.

My problem now is that there is a metallic cracking noise coming from the rad cap area , combined with  the expansion tank "puffing up" at the same time.
When removed the rad cap , a load of coolant rushed into the expansion tank ......

I have changed the thermostat as the larger rubber hose facing to the front  was not getting hot and that now seems to be working. The temperature warning light does not come on but when i try to start it there is a bubbling sound from the expansion tank. i have not completely drained the system , but i have bled the system as per the manual ie cap off , open the bleed screw by the chain tensioner until no air comes out , and refill to the bottom of the neck, but still it continues to drain into the expansion tank (the rad cap is new too) and i have to drain some out. If i open the bleed screw some air does come out. I have replaced the oil and filter after the valve buckets were replaced , and there is no change in oil level or signs of water contamination.

I am obviously missing something here, and i hope that some one can help me ....

Kind regards kmac
Parent - - By alunt Date 09.08.19 15:55
Possibly head gasket? If it’s leaking from the cylinder into the coolant system the compression will push air into the coolant. A compression test could help diagnosis.
Parent - By aware Date 09.08.19 17:06
Smells head gasket issue.
Temp light will eventually turn on after some more wear.
Bubbles while the engine works possibly means that combustion gases leak to the coolant circuit.
You can test compression with a tester but the surefire thing is to open head and look.
There is a poor's man solution to pour a "seal-a-gasket" treatment and hopefully save it.
I haven't tried it so I don't recommend.
Parent - - By HelmetHair Date 09.08.19 17:07
As Alunt says, sounds like possible head gasket gone —-due to overheating after the thermostat failed???
How exactly is the expansion tank “puffing up”? The lid is only loosely held on (the one behind the seat back-yes?)

Who did the valve clearances?

Oh—and does the hot warning light come on with ignition? Does it light up at a all?
Parent - - By mac140 Date 09.08.19 17:21
Hi all , thanks for your replies.
I suspected head gasket , but there is no smoke from the exhaust, the oil is not contaminated and level correct. Is there another coolant valve or bleed point somewhere that i am not aware of? When turning the engine over it is not whizzing quickly. The coolant light does come on with ignition and self checks. I have taken the plug out and there is no coolant smell (just fuel , because it wont start)
The expansion tank puffs up in time with the metallic click from the rad area (like a lung working - approx once every 30 secs.
Have i bled it properly, is there a more foolproof way of doing it.
If it is headgasket, what sort of job is that as my mechanical skills are ok ( i did the valve clearances , and they are now spot on)

Again, thanks for your time and help .
Parent - - By alunt Date 09.08.19 21:17
Try a Gunsons compression tester with suitable adapter for the spark plug size. If the head gasket is leaking it will soon let you know. Compression needs to be at least 11 bar, preferably 12 plus when turning the engine over on the starter with a good battery. If your engine is turning over slowly you may need a refurbished starter motor or better battery before you can get a proper compression reading.
Parent - - By mac140 Date 12.08.19 15:06
Afternoon gents.
Thanks for your replies, seems like the head gasket it is then. Will locate a compression tester and update once i have tested . When i stated the engine is not whizzing over, i meant that it is turning over normally , not like it has no compression at all (just to clarify).
Do i go genuine with the parts or can someone advise the best place to get the kit, and can it be done in situ or engine out ? is there anything else i should look out for?
Thanks all
Parent - - By alunt Date 12.08.19 15:28
I get head gaskets from BMW, I've not found an alternative. Make sure you order one for the right engine size.

It's an engine out job as far as I'm concerned. Getting it out isn't such a huge job as long as you don't come up against corroded exhaust nuts or similar types of hurdles. Once out all jobs on it are so much easier.

You'll need a torque wrench and a way of tightening the head nuts, which are difficult to access. For the inside ones I use a small socket set of decent quality, which will stand the torque. For the external ones I use a swivel headed double ended ring spanner of decent quality, and attach the torque wrench to that when it's 90 degrees to the nut.
Parent - - By mac140 Date 12.08.19 16:52
Thanks. will price it accordingly. The exhaust will come off easy enough as been off recently. I have torque wrenches etc. My only concern is the condition of the electrical plugs up by the right seat belt catch area (to starter etc, i think)
Anything else to check whilst it is on the bench? What work required to rekit the waterpump ??
Many thanks kmac
Parent - - By alunt Date 12.08.19 17:26 Edited 27.08.19 19:10
Check the valve clearances and adjust if necessary, much easier with the engine out. I recently had a lower cylinder gasket leaking, a cheap part but engine dismantle required to replace it. Piston ring compressor useful for this job. Water pumps do wear out, not a big problem to replace with the engine in the bike.
Parent - - By mac140 Date 12.08.19 18:08
The timing chain etc were ok when I had the camshafts off to do the valve clearances (  the original fault , ironically) I do have a waterpump kit here ,so will do that at the same time
Thanks Andrew, will let you know how  i get on.
Parent - - By rockstedy Date 09.08.19 21:48
It may be good idea of recording video and share YouTube link with us/your bike problem.
Parent - - By aware Date 10.08.19 04:46
Yes, better make a video with the bubbles in the expaksion tank.
Head gasket blown can have several versions of damage. It can be in your case a tiny "hole" that allows only gases to enter the coolant circuit and not (yet) the opposite. It has to do with where exactly the head gasket has been damaged.
Parent - - By mac140 Date 27.08.19 16:40
afternoon all
Got myself a compression tester and tested the engine twice ( from cold) turned engine over for approx 10 secs. each time. Results were 13 bar and 14 bar respectively. Bizarrely the engine has stopped pumping coolant everywhere but i can still get air out of the bleed screw. How do i know when the coolant is full as when i topped the rad up to bottom of neck (as per workshop manual) refitted the cap and turned it over , it flowed a lot into the expansion tank . i have drained this off and will try again tomorrow. road test seems ok but cuts out at junctions ( restarts on the button , got a new plug in today)
Any ideas ......?
Parent - - By aware Date 27.08.19 17:57
Cutting out at junctions:
Spark plug worn
Battery terminals loose
Idle valve defective (rare)
Injector seal
Intake manifold cracked or loose on head (rare)
Early symptom of burnt valve (rare, usually accompanied with difficult starting)
Parent - - By mac140 Date 30.08.19 19:17
Hi all

Confirmed the injector leaking air with brake cleaner, thankyou. I have removed the injector and cleaned the big seal , when refitting ,it does not seem to go right to the bottom (i.e 2mm sticking up over the housing) Is this right, as it does not seem very tight on the injector. I have tried an additional O ring seal on the bottom of the injector seat and refitted , but to no avail.
Also i have noticed that the injector swivels in it's housing when the injector rail is correctly fitted  (could not refit the electrical plug, until i worked it out), is this right as well ?
Is there a seal at the top which needs replacing? What seals are available, i read on here that the big seal is not available separately ??
Had a new plug couple of days ago, and always restarts straight away after cutting out. Compression OK and valve clearences spot on.
IS there an easy check for the cooling fan, as I have not heard it come on once whilst I have been trying to sort this out , the fan turns by hand so not seized.

My thanks to you all for  your help
Parent - By alunt Date 03.09.19 12:55
Assuming you’ve got the correct sized O ring in now, you can either seal the large ring with sealant or build up layers of a suitable tape on it to help it seat better. I use self amalgamating tape.
Parent - By patc50 Date 27.08.19 17:58
I can't comment on the coolant problem but the cutting out at junctions and restarting easily can be a symptom of air getting past the injector.  With the engine running, spray some brake cleaner (aerosol) around the injector - if the engine note changes (speeds up) air is getting past the injector.  This can mean a new 'O' ring on the injector itself or some sealant to seal the gap between the rubber/metal insert that surrounds the injector in the inlet manifold.
Hope this helps.
Parent - - By alunt Date 27.08.19 19:09
Compression sounds ok, so head gasket may be ok as well. If the coolant problem is settling down try running the bike round for a few days and monitor the header tank and sometimes the filler cap level.
Parent - - By mac140 Date 04.02.20 16:19
........Well that will teach me!! Head gasket finally expired  (in the garage luckily so did not seize....) So engine out, easy according to some posts on here. All going well until i try to remove the rear pads / caliper to get the wheel off. The pad pin will not knock out ( from exhaust side to wheel if it is the same principal as the front) WD40 applied , but does anyone have any tips to help remove the caliper/ wheel assy if i cannot remove it. How can you detach the caliper from the carrier , if that is possible???
Parent - - By rockstedy Date 04.02.20 18:43
You can remove rear wheel together with rear calliper/alloy bearings holder.
Parent - - By mac140 Date 05.02.20 11:52
Hi rockstedy, thanks for your reply.
How do you remove the whole ? do i disconnect and drain the brake system at the caliper, because even with the pads out, would there be enough clearance to remove the disc/ wheel ? with the large 6 sided nut removed do i just slide the wheel off, what must i watch out for  on dismantle and refit? Sorry if this seems vague but all help is appreciated.
Parent - - By aware Date 05.02.20 12:09
Are your brake pads very tight? That's the problem?
If then I will give you some info. Please reply.
Parent - - By mac140 Date 05.02.20 12:48
Hi aware. thanks for your reply. No the pads are free on the pin and move easily. I just cannot get the pin out of the caliper to remove the pads etc. I just have this and then the main (long) bolt underneath to remove then the engine will be out ..... Thanks for your help.
Parent - By aware Date 05.02.20 13:25
To my understanding you can just push out of the way the caliper along with the pads out of the way. I certainly didn't extract the pads when I removed the engine. I remember the caliper along with the pads hanging after the engine removal. Possibly what you miss is the fact that after popping out thw wheel half way then you can remove the caliper (with pads on).
Parent - By rockstedy Date 05.02.20 22:32
Hi mac140,
Undo rear hex nut a bit, remove exhaust ( cylinder head nuts may require extra effort to remove), squeeze rear calliper so there will be extra room between pads and disc so easier assembly afterwards, rise rear end even with simple scissors lift so tyre won’t touch ground, remove rear nut completely, now you are free to take whole rear wheel from axle. Please note correct position of spacer between alloy wheel rim and rear end bearings. There is sufficient length of flexi rubberised brake hose from frame  so no worry. If your bike has silent pack ( exec) sometimes plastic housing inside require to deflate tyre before removal and overall may not be so smooth. Hope it helps.
Parent - - By BOR Date 05.02.20 16:11
Pin Removal is exhaust side to wheel side as you say.

I found it very, very, difficult to knock out last time, but it did eventually fire itself out of the caliper. Don't give up too soon.

(I'm assuming you have pulled the safety pin out first? )
Parent - - By mac140 Date 06.02.20 12:45
Hi all , thanks for your replies, all support gratefully received. After panic subsiding, yes there was enough to get the wheel out so that is done, just leaves main bolt removal to drop the engine out. Still need to get the pin out of the caliper as it does need new pads Whilst the wheel is off is there anything else to grease / lube/ adjust ??
Parent - - By aware Date 06.02.20 15:41
WD40 works wonders. Try this first.
Parent - By variobob Date 06.02.20 21:27
Although I am not present too often on the forum anymore, I do want to warn any not too experienced diy mechanic to combine brake calipers with WD40. Yes, it is wonderful stuff, but if you decide using it please notice that both the disc and, more important, the pads should in no way get any WD-spraydrops. One of my clients once got rid of a squeaking sound from his front brake. The solution was WD-40. He added the stuff whilst the brake caliper was still mounted, so with the pads in place. As the pads themselves absorb the oilish moisture that WD-40 is, the braking power was lost completely after the third or second time that he used the brake. Therefor, please take notice when using WD40 in the brake caliper area. Last thing: if you use it properly, you still should clean the caliper / brake pad bracket with disc brake cleaner or other degreaser. One does not want any greasy residue to spoil the braking action.

My comment is not meant arrogant or as a show off. Please just read it as a simple caution for any first timers that come accross this thread on one of the best forums the EU ever new.


Parent - By rockstedy Date 06.02.20 20:25
Clean all parts with brake cleaner/degreaser. New white grease on rear wheel axle, cooper grease where pads touching metal guides/piston, worth to renew graphite grease on moving pins of brake calliper. I also spraying silicone grease on sides of piston before pushing it in. Please check for visible unusual wear/damages/corrosion especially of calliper metal pin holding pads in correct position.
Parent - By HelmetHair Date 13.08.21 21:35 Edited 17.08.21 12:45
I eventually got this out last week.

Removed the brake carrier with the wheel, positioned the caliper on the floor (still connected via the hose) , supported the area so the carrier couldn't crack and WACKED it with a punch using a 5lb club hammer.
Went back in easily and oiled for future ease of removal.
Up Topic C1 Information / Repairs - Faults & Fixes / My C1 overheating ( or not....)

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