Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Timing belt issue 1990 Plus 4 M16

Hi
Out for a run couple of arvo's ago. Clocked over 100 miles, hot day in low 30's and all running well until a bit of a horrible noise, (sounding like loose gravel hitting the underside on a newly sealed road!), with the engine immediately dying and not restarting. Late afternoon so called in tilt tray tow truck from RACQ roadside assist to get back home, about 35 miles. Suspected broken timing belt?
Checked out next day but timing belt not broken. Removed all the spark plugs,and suggestion was made to see what the compression was like by putting hand over the openings. It felt like less compression on the 2 front cylinders.
Back to the timing belt and moving the crankshaft around it looks like the timing belt has jumped a cog or two on the sprocket?? (Belt is quite firm then goes slack as the crankshaft is turned a bit more. Although belt doesn't look perished and no visible cracks, it has got a couple of nicks in it as if it may have got caught on something?).
Anyone else had a like issue? I'm in the process of ordering a new cam belt.
Having not investigated further yet, guess I'm wondering whether the valves and anything else will be damaged as well?
Appreciate any thoughts.
Col.

ps: (Motor was completely rebuilt 12 years ago with new water pump and timing belt and only done about 5000 miles since. Receipts show a new tensioner purchased in 2015)

If only front 2 cylinders have low compression I'd suspect a bent valve and/or piston damage on those .... the fact it made noise that loud indicates something came into contact with something it shouldn't .... let's hope I'm wrong and it's something else entirely.


K

The belt should be replaced every 5 years irrespective of mileage. Depending upon how far it has jumped the valves could have hit the cylinders so you will need to strip the head off to check. I guess you might be able to see inside via the spark plug holes with a boroscope if you have one. But it sounds like there is damage by the lack of compression.

I'm with Keith and John on this one.

The M16 is an interference engine so its possible that there could be a bit of valve damage.

Have you popped the cam cover off to check if the cams have broken? Not unheard of when a belt jumps

If they are ok, then it might be worth fitting the new belt and see if you can turn the engine over which would prove damage to the valves without whipping the head off - save the costs of a new head gasket set, bolts and a skim in a machine shop?

Arwyn

I am puzzling as to why the belt goes from tight to loose when rotating the crankshaft. I would be looking to see if a shaft or pinion is bent or running out of true somewhere.

I assumed the belt had been damaged in certain places.

Unfortunately the M16 plus 4 has the water pump as a part of the cam belt drive, later the water pump was changed to auxiliary belt drive on the later T16 engine. The turning of the engine by hand shows it going from tight to loose,,,,have you tried taking all plugs out and turning engine by hand. As rechard says have you lost teeth on the cam belt.

looks like lots to look at please report back with what is found, if youre changing cam belt its worth putting in a new water pump!

Manuela etc required then I may help, my engine is the T16.

I plan on changing the belt and water pump on my M16. Here's the rover tech video

Rover - Rover Professionals - Technicians Update 3 (1993) https://youtu.be/2UhWenKlhGE

Interesting note at the end. total new belt deflection should be less than 6mm. The gauge is only used as a reference which was a change. Anyway, the 6mm deflection between the cams from horizontal was interesting (haynes claims 19mm until you can get to your rover dealer!!).

Hi all,
Thanks for your replies and suggestions and the Rover tech video. It all helps

Doing a bit more investigation and looks like I’ve found the culprit! Taking off the bottom timing belt cover and found this ¼” bolt floating around amongst the machinery. Not just sure where it has come adrift from yet? (For the picture I’ve placed it on the belt here near the major tear across the rubber.)

https://www.dropbox.com/s/2bnqhpdow97ijea/Timing%20belt%20tear.JPG?dl=0

Doesn’t appear to be any broken teeth on the cam belt, just the tear and a couple of other nicks on the side.

Seems the timing belt cover on my motor differs to the pictures in the Haynes manual. Trying to find the bottom mark to line the crankshaft sprocket up to that on the motor so I can then check the camshaft sprockets to see how far out the alignment is. As I manually turn the crankshaft, in the loosest position I can deflect the timing belt almost 40mm so maybe a tensioner has come loose as well. New belt ETA next Tuesday all being well.

Next I’ll take off the cam covers and see if I can check any damage to the valves. (my “bush” mechanic ability not so hot so will probably call on someone with more skills than myself for some help). Expecting we’ll need to take off the head possibly. If it comes to that, will need to source gaskets for the head and cams? I’m in Oz so not sure if they will be available locally yet or not.
Regards,
Col.