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Post by dave1800 on Mar 18, 2018 7:49:00 GMT
I have been asked whether you have checked the radiator for cold spots - I appreciate you had it re-cored - but maybe still a possibility?
David
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Post by paddymk2 on Mar 18, 2018 11:04:45 GMT
Hi Dave I just ran this check at idle ~ 700rpm and I didn't have the engine hot The initial vacuum was about 14-15 Inches Hg, the angle was about 11-12 on the tongues with the spectroscope. I turned the distributor anticlockwise to get 17 inches Hg (I estimated by about 10 degrees) and the spectro reading was about 25 degrees total (Pic) Hope this makes sense Regarding radiator cold spots - I suppose I could probe the surface with a thermocouple? Regards Paddy  |
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Post by dave1800 on Mar 19, 2018 1:22:16 GMT
The easiest way to check for radiator cold spots is to use your hand checking as the engine warms up. You will need to stop the engine each time you check of course when you do this.  A thermocouple could be used but it records tthe temperature at a single small area whereas your hand can move across the whole radiator surface. A thermal image camera would be ideal - but expensive! The vacuum increase with ignition advance of around an additional 10 degrees is marginal but the vacuum is still low. I think I really need an engine hot reading to take this line of possibilities further. Can you also check the vacuum reading without advancing the ignition but turning the throttle idle screw so you get a steady engine speed of around 2000 rpm. Do you have or have access to a compression gauge? I can't recall if you have done this already? David |
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Post by paddymk2 on Mar 20, 2018 9:10:18 GMT
Hi Dave
I've borrowed some tools to do a compression test.
I 'll have another check on the timing. Meanwhile I snapped off the bolt on the trunnion for the choke cable (drat) while checking it was ok and not sticking - I might have to cut that off and get a new cable as well...
Anyway I can't do too much in the evening as its a bit noisy and I don't like being in the gloom when I'm up and under the car and taking off wheels.
When doing a compression test - do I need to do anything more than crank over the engine? (Just watched the video of the MG guy - pull all the plugs then cranking the engine for about 10 turms. - he didn't seem to do much else.)
Cheers
Paddy
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Post by andrewa on Mar 20, 2018 11:15:48 GMT
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Post by paddymk2 on Mar 20, 2018 12:30:01 GMT
Thanks Andrew - well yes and no, its really interesting to work on these things. If it was straight forward Id not really learn. and the level of advice is really focussed.
cheers
Paddy
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Post by dave1800 on Mar 21, 2018 0:03:43 GMT
Had a quick look at the article - a couple of comments. Black smoke = unburnt fuel, white smoke = oil burning, steam whe engine hot = possible head gasket leak (check for oil floating on top of water in radiator and water in oil - emulsion on dipstick) Check with a cold engine and again with a hot engine -take care when removing spark plugs Make sure the engine isn't run rich before checking eg with choke on etc as the excess fuel will wash away the oil from the ring / cylinder sealing and can give surprisingly low and misleading results. David |
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Post by paddymk2 on Mar 21, 2018 1:54:39 GMT
Hi Dave,
Thanks for the comments about temperature.
With all the adjustments with ratio etc and the intention to avoid having it too lean (and too hot)- the ratio is rich (black smoke and sooty plugs) so should I try to correct this first?
Also should I have my foot on the accelerator when doing this test to keep the throttle valve open fully?
Best regards
Paddy
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Post by dave1800 on Mar 21, 2018 6:43:38 GMT
Good questions. Don't worry about the mixture yet we will sort this out shortly after the compression test which could lead me to ask you to carry out a slightly more challenging test taking measurements but little spanner work and no specialist tools needed. You will find that checking the compresion with the throttle closed or wide open will make very little and probsbly no difference. We are looking for even compression across all 4 cylinders as well as the absolute values. 10% variation is acceptable, some work on 15%. regards David Hi Dave, Thanks for the comments about temperature. With all the adjustments with ratio etc and the intention to avoid having it too lean (and too hot)- the ratio is rich (black smoke and sooty plugs) so should I try to correct this first? Also should I have my foot on the accelerator when doing this test to keep the throttle valve open fully? Best regards Paddy |
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Post by dave1800 on Mar 22, 2018 10:08:40 GMT
I forgot to mention - when you do the compression test with all 4 plugs removed, try turning the engine using the fan belt held against the fan pulley to stop it slipping to see if it is easier than when you did it a while ago.
David
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Post by paddymk2 on Mar 23, 2018 2:15:43 GMT
Will do, but I'd be really surprised if its easy to turn from the fan belt. I know I had the plug in when I was setting it at Tdc, but it still felt stiff pulling on the spanner on the end of the crank.
By the way when bringing the engine to 10 before tdc the manual said to bring it to tdc and then wind it back 10 degrees. Is that likely to have any difference?
Also could the fan belt be too tight? I can sort of twist the belt by about 45 degrees easily enough by hand.
Regards Paddy
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Post by dave1800 on Mar 23, 2018 4:06:14 GMT
The fan belt should have about 0.5" just over 1 cm of play in the longest span. If overtightened it may damage the water pump and alternator bearings.
Don't worry at this stage about turning the engine back to TDC and then to 10 degrees BTDC at this stage, that is to try and cancel out backlash in the distributor drive - timing chain, distributor drive gear etc. A stroboscopic timing check is far more accurate especially on an old engine.
You wouldn't be able to turn the engine using the fan belt with the spark plugs in. I've never tried this on an automatic crab. It may be normal for it to be stiff as the torque converter incorporates an oil pump that pressurises the transmission and as I understand it this operates in park and neutral.
Can anyone here with experience of an automatic crab confirm please/
regards
David
Edit: Yesterday, I tried to turn an old small Nissan auto engine over after removing the plugs and it was possible using the fan belt, not sure if this is comparable?
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Post by paddymk2 on Mar 27, 2018 13:52:07 GMT
Hi Dave, Didn't get too far - the fan belt tension looks good, but couldn't get it to turn by pulling the belt. I looked through the manual regarding the Thermostat. It suggested a lower temp device (74oC) for hot climates. Also Tridon link show a high flow version (30% more) also suitable for the 1800. I have their standard flow version (82oC) so I'll swap it over. I couldn't get the compression gauge to fit properly (its an old type with a fat rubber tip) I'll pick a screw in type from the shop. Also after a warning conversation with my daughter - "Dad I don't want to hear on the evening news, that: A man was killed today when the car he'd been fixing after watching Youtube went out of control and crashed..." So I've agreed to book it in at the friendly professional mechanic. The guy's also a British wizard. Though I am a bit concerned that he'll tell me that the gearbox is a bag of old bones or something similar... Regards Paddy |
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Post by Penguin45 on Mar 27, 2018 14:16:01 GMT
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Post by dave1800 on Mar 28, 2018 1:22:45 GMT
Hi Paddy
I wouldn't worry too much about the automatic gearbox if it's changing smoothly and the ATF is fresh. As I mentioned I've not tried to rotate a crab engine attached to an autobox. I did try a small engine Nissan but that was an inline configuation (RWD) so possibly not comparable. Unfortunately no one here with an auto responded.
The other checks I will suggest after you have compression readings don't involve anything more dangerous than turning the engine over so hopefully that and letting an experienced mechanic give the car a check up will stop your daughter's nightmares.
Possibly now is a good time with Spring weather arriving in the northern hemisphere soon (I am led to believe!)to suggest everyone considers a professional check up for their cars once a year now the MOT requirements have been removed for the crabs in the UK.
David
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A thermocouple could be used but it records tthe temperature at a single small area whereas your hand can move across the whole radiator surface. A thermal image camera would be ideal - but expensive! 
