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This following question has been asked by someone who wishes to replace the timing chain on their Standard 23C engine.
The Question…
I am trying to read the lines between the Engine Rebuild DVD and the Workshop Manual on the subject of Timing Chain Replacement.
I am pulling off the front of my ’59 MF35 4 Cyl Diesel (to get the radiator recored)….so my thinking is “Why not replace the timing chain and tensioner while I’m there?”
Do all I have to do is turn the engine to TDC, hold it with a pin in the flywheel, remove the chain and tensioner and replace…ensuring that the small bolt hole in the camshaft gear matches up when putting tension on the left side of the chain?
Second question, “Would I then have to retime the fuel injector pump afterwards?” I have no idea if this is going to be more complicated than its worth…..the timing chain and tensioner may be ok…..but why not do it, eh?
The Answer From VTE…
Firstly is the tractor starting and running OK. If it is all OK, then maybe you don’t need to replace the chain and tensioner.
You can remove the cover to inspect the chain without disturbing any of the timing components. Look to see if the chain links fit on the sprocket teeth centrally (as shown in the DVD). You can replace the tensioner without removing the chain (and without disturbing the timing).
The setting of the valve timing (which is controlled by this chain) has to be done with number 1 cylinder on top dead centre on its compression stroke (i.e. both valves closed). The timing hole in the flywheel holds the engine at 16 degrees before TDC which is used for the injection timing – which is timed after the valve timing has been set using the chain.
If you choose to remove and replace the chain then you will need to follow the timing procedure as per the DVD. Once you have set up the timing of the chain you will need to check the timing of the injection pump.
Thanks…
Cheers, you’ve given me the exact info I’m looking for….the tractor is unrestored, but running ok…I get the difference in valve timing vs injection timing now…I hadn’t picked that up before.
So if I replace the timing chain, I’ll need to set up the chain timing and then follow up with the injection timing. Got it.
In my case, I think that I’ll just do an inspection. I just remember rebuilding Standard Engines (Triumph TR3’sand 4’s) back in the day and the timing chain and tensioners were always suspect and had to be done every 30K miles….with this tractor, who knows?….no idea of its maintenance history…but there is no rattle.
Hi Conrad,
I’m afraid your friend is probably correct.
So what happens is… when the oil is cold and thick in consistency it cannot flow through the bearings particularly easily and thus the lubricating oil pressure is maintained. When the oil gets warm it will flow more easily through the oil ways and the bearings (the bearings being the part of the system where the greatest resistance to flow occurs), and then the pressure will drop. This is made even worse if the oil pump is also worn.
The pressure gauge will likely be reading correctly, as it is showing a change in pressure when the engine gets warm. Likewise, it won’t be the pressure relief valve given those symptoms.
Could it be just the oil pump? Yes maybe, but nine times out of ten I would expect it to be wear in the bearings. Most people also replace the oil pump at the same time whilst the engine is dismantled. Then when you get inside it you will probably end up doing the cylinders/pistons/rings etc. as well.
If oil pressure is getting low then it is definately time to dismantle the engine and rebuild. I’m afraid it is inevitable.
The Vintage Tractor Engineer
hi, i have an mf35 about 1961 with a3-152 perkins diesel. My question is when i run the tractor for about 20 minutes or so i start losing oil pressure, when i raise the idle the pressure comes up some, what would be the cause of that, a friend of mine suggested my crankshaft bearings may be worn out?