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Smoking xflow


alextangent

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I drove the 7 to and from work last week, and I'm noticing heavy puffs of grey smoke when taking off from lights. Done the following checks;

 

1. Oil level is at max on the dipstick, doesn't appear to be burning much oil?

2. Oil overflow tank is empty, no smoke from overflow hose

3. Smoke comes out of the rocker cover, a bit more than it should I suspect, some back pressure in there

4. Worse when the temp rises (fan kicks in at 82 on the gauge, don't know how accurate that is)

5. Worse when the engine has been idling, definite misfire and light smoke.

 

I've done a compression test, pretty inconclusive. I may not be doing it right though; is the recommendation to remove all plugs, disconnect fuel pump and do it at full throttle open?

 

Does this sound like a head problem? It's unconverted, but I'm running with a Castrol fuel additive.

 

Edit: Added to say it's a 1700 supersprint, 25000 miles, unmolested afaik.

 

Alex McDonald

PASSED THE MOT!!!

 

Edited by - alextangent on 12 May 2008 11:27:50

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Nope - all crossflows don't do that.

 

Compression test - IIRC take the plug out on the cylinder that you're going to check.Leave the rest in. Carry out with Fully Open Throttle.

 

Sounds to me as if engine getting towards needing a re-fresh - ie new rings etc.

Some would say that anything above 18kmiles on a supersprint 1700 with cast pistons is about when you might expect to start to need to do a refresh. (Others would say you can get 40k miles, but 25k miles is in the ballpark).

 

Doesn't sound like valve problems, though might not be being helped by worn valve guides.

 

X-flow(er) power now resting. Trying Vx for a change.

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Well, yes, but it's got much worse. Like a cloud of smoke on pumping the pedal...

 

I'm going to try another compression testing session.

 

Found this link here abut making a leak-down tester for around 20 quid. Cool *cool*

 

Alex McDonald

PASSED THE MOT!!!

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So what would a refresh cost? Or should I be looking at a new crossflow from a reputable builder? I did have a 711M I bought last year, but it wasn't in such great shape when stripped back (the bores were glazed).

 

Alex McDonald

PASSED THE MOT!!!

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Grey? Blue is oil, white is water, black is fuel.

 

Why are you suspecting oil?

 

If the smoke is blue, and happens when throttle prodded after sitting idle...likely valve stem oil seals. Cheap as chips.

 

Willie

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Not too good with colours... Suppose it's blue. Definitely not black.

 

So how do you fit them? Some hits on searching about double spring setups not being too happy with the seals.

 

I'll do another compression test and if it's the head, whip it off for a refurb. I had the head off at 14K miles due to knackering an exhaust caphead screw, and should really have gone down the route of getting it unleaded etc then. The bores were in really good shape, no glazing, but that was 11K miles ago now. Any recommendations for a good head specialist?

 

I'll report back...

 

Alex McDonald

PASSED THE MOT!!!

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Good head specialist... Fffnnaarrrr 😬

 

Alex, if you need help looking at colours, let me know ans I will come over. Got the trigger wheel and crank pulley done, need to set up the sensor bracket so could drop by one evening...

 

She is nearly ready for the MOT.. new diff, new suspension, lots of cleaning and painting... summer time is here..

 

Jon

 

-----------------------------------

Ital or Ford... the choice is yours....

 

Hmmm, I'll have the ford please Bob.

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If you do not have a PCV valve fitted (and I don't think that many Caterhams do) you will always get some oil vapour coming out of the oil filler cap. Providing it is not enough to make the rocker cover look damp (shiny) then they all do it.

 

Sorry, just read point 2 in your original posting and you may have a blocked PCV valve. If it worries you, then try changing the valve first.

 

There are modifications where you change the filler cap type and put in a tube to a catch bottle so that you don't see it and can monitor the amount of loss - but that may be extreme overkill.

 

I have a little damp patch on the mats in my garage under where the engine would be. The area concerned is about 30cm by 45cm and looks very worrying until I try to clean it up and realise that there is probably less than a tablespoon of oil down there.

 

So long as you do not see any oil loss on the dip stick and the compression tests show even pressures on a warm engine with all plugs out and turned over for say 10 revolutions per test, then I would not worry.

 

If pressures are not consistent and cannot be fixed by checking the tappets, then it is probably time for a refresh.

 

Mine is 36,000 miles old with a reworked head for unleaded but the bottom end is standard and original.

 

Cheers,

 

Graham

------

Low tech luddite - xflow and proud!

 

Edited by - Graham Sewell on 13 May 2008 09:36:33

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PCV valve? Is that the valve the size of a small briefcase on the crankcase with the overflow hose coming out? If so, I've got one. I would have thought that excess crankcase pressure would have forced oil out of the dipstick though, and I'm not seeing that.

 

JonB; cool, call me. I'm away this weekend and next week in Italy on biz, but I'm around after that.

 

Alex McDonald

PASSED THE MOT!!!

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No PCV valve; I checked tonight, and the engine vents to the bottle. There's no valve inline. I.e. it's at atmospheric pressure. This would appear to be less than ideal, as the cankcase should really be at less than atmospheric pressure 🤔

 

Alex McDonald

PASSED THE MOT!!!

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Alex,

 

Re the vale stem oil seals, I haven't done much work on XFlows, but someone will shoot me down if I'm talking jibberish and this doesn't apply to your engine.

 

They're usually hiding under the valve springs, and so you need to remove the rockers/rocker shaft assembly and valve springs to get at them.

 

This can be done with the head on, but for all the hassle it is, I'd just lift it off. To do it with the head on, you can push rope in through the plug hole, then bring that piston up, so that the (SOFT) rope holds the valves closed and you can then use a suitable spring compressor to get them off.

 

Some people use an adaptor like a spark plug, connected to an airline and put air pressure in the bore to keep the valves from dropping. I never liked the sound of this...but I've always just pulled the head off anyway (I'm a gluten for punishment. Last week I removed my engine, simply because I was given an engine crane).

 

Willie

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Alex, forget the Dizzy.... ;)

 

Actually, I will have mine up for sale once the Megajolt is in... this is modified for 9-12 degrees at 900 rpm -> 36 degrees at 5500 rpm... only done about 500 miles since being re-built...

 

Jon

 

-----------------------------------

Ital or Ford... the choice is yours....

 

Hmmm, I'll have the ford please Bob.

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