Hard engine knocking, help needed!

Gerald1961

Gerald1961

Member
Hello together,

I am quite a newbie to the model a after having bought a nice 155C from a dealer in the netherlands 1 1/2 years ago (my avatar). In the meantime I became quite familiar with the wonderful car and the technique, doing all services on my own after L.Andrews` literature. This fine status lasted for ca. 4000 mls.
Yesterday we got a serious and lasting problem: Engine knocking during idle and increased rpms. The engine temperature was normal as ever. No coolant leaks, no excessive oil consumption. Reading L.A. I first thought of a stuck valve. I injected ca. 50-60ml engine oil into the carburettor during idle, as L.A. proposes. Some blue clouds, then we had a calm and smooth engine. The hard knocking had disappeared. I was happy about my simple fix, my wife smiled and we continued our trip back from holidays. After 10 mls. the noise reappeared, a little bit louder than before. Then I stopped and decided not to continue our trip and we got 300mls towed home...

I checked the ford barn and utube. I did not find a lot about my exact problem. But this video somebody posted @ utube, it is exactly my noise and my symptoms. Unfortunately, there was no clear explanation or solution explained.

https://www.youtube.com/watch?v=871TLjDWOlg

Who can help me in diagnostics?

Thank you in advance for your answers!!
 
That's a sticking valve. Try changing your oil but add a quart of marvel mystery oil as your first quart. Top it off with the regular oil don't over fill. MMO is a light oil so it burns off quicker than regular oil so monitor you oil level. I would only add it once per oil change. If it helps a little do it again at the next oil change. I would also add a little to each gas fill as that will help sticking valves too. Read the can for how much.
 
I have the same problem with the identical noise . At first I thought I had lost a big end or maybe some kind of piston problem . I pulled the pan but all looks good and tight down below . I have no compression on no 2 cylinder i Pulled the valve chest cover and the valves go up and down,no sign of sticking . I will now take the cylinder head off but right now it will not budge so might take a while .I will inform you with what I find . I am insured with Hagerty UK and their service on a late subday afternoon was superb quick efficient recovery to my front door (100 miles)

John in rainy Suffolk County England.
 
Check cam gear pull side cover off and look at it also check crank shaft end play
Mine was the thrust bearing in the oil pan :-( I will be pulling engine out this weekend to check main bearings IMO my timing gear fibers clogged the oil passages,overheating bearing cracking the thrust bearing.i would not drive your car until your problem is fixed
 
If the noise went away with the oil in carb treatment, likely it is a stuck valve. Try a heavy dose of automatic transmission fluid in the fuel. I would say at least a quart for a tank of gas, then run a couple oz per tankfull indefinitely. ATF is an old mechanics trick, solves many issues.
 
John Charlton -
Although now too late because you have removed the manifolds and valve cover (valve chest cover???), there is a way to pop a stubborn head loose without a puller. Drain the coolant and remove all the cylinder head nuts. Then start the engine. It may run for a couple seconds before the compression and firing in the cylinders pop the head off the engine block enough to finish pulling it up over the studs. I'd like to see someone post a video of this procedure. It should prove informative, as well as entertaining.
Marshall, whose head is already loose
 
This tool has helped pull several rather stubborn heads in our club:
 

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Thank you all for your answers! My plan to proceed: I do not want to run the engine without getting a step closer to diagnosis. First idea is to glance with an endoscope into all four cylinders ( all without plugs ) crank the engine by hand and observe if there is any irrregular movement of a piston indicating a defect or worn wrist pin or to see a stuck valve. If this is possible, I do not know, but i do not have to run the engine or dissassemble in the first step. I also ordered a stethoscope, which should work better than a screwdriver to localize the source of noise on the running engine. If this does not bring any news, IMO I should remove the oil pan ( After draining the oil ;-) if I can observe any irregularities. This is the step John already did.
 
A sticking valve due to deposits on the stem may move OK at cranking speeds but hang up when running (even at idle).
 
that noise is neither a dull knock (main bearing) or a sharp knock(rod),its more of a slap, I would look for a broken piston
 
I will keep you informed about my glance into the combustion chambers. But I do not have a video grabber for my endoscope. So I hope I can take some photos from the screen.
 
@Big Hammer: Did your engine suffer from the same ugly sound as ours does or did you discover other symptoms?

I am just coming back from the car where i took some videos of valve movement by hand cranking and some photos from valves and pistons. I will post them ASAP.
 
Sounds like a possible blown head gasket. A compression check should show a lack of compression in 2 adjoining cylinders. This can be checked by removing all the plugs and using your thumb over the plug holes and turning the engine with the starter. You will notice the compression will try to push your thumb off the hole if the compression is good. If it is bad there will be no resistance. You can also run the engine and observe the rear of the carburator and see if you have compression coming out of the opening when the throttle is opened suddenly.
 
In your video, the tapping sound is an exhaust leak, probably at the front of the exhaust manifold. I could not hear the hard knock so, I can't diagnose it. To find an exhaust leak, use a length of fuel line as a stethoscope to listen to the manifold connections.
 
Now some Photos from interior. Quality of the photos is very poor, but all 4 cylinders move as regular as the valves while cranking.
 

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now the valve chamber. At cyl1 valves there are some metal flakes. They look as if they shouldn´t be there.
 

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Here the whole staff. Nothing what sets me up but the flakes. Any comments, ideas?
 

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@ James: I am pretty sure that there is no leak from the exhaust manifold. The knocking sound is metallic hard. And a leak would increase the noise level by load IMO.
Head gasket might be, but I do not find oil the coolant or vice versa.
I will do the simple thumb compression test.
 
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