Oil pressure drops when cornering or braking
My overdrive has stopped working
One of the biggest Scimitar weaknesses is the presence of a nylong or fibre gearwheel which transmits the crankshaft rotation to the camshaft, and also indirectly drives the distributor and oil pump. If you want to change the timing wheel before it breaks, read this page. Otherwise, if you are unlucky enough to have had the crunch, read the rest of this article.
The long-term repair is to fit a steel wheel. Before doing that, you have to clean out the debris from the sump, then assess and repair any other damage which might have occurred. Prepare for a long and dirty weekend. When I did this job I had no garage and completed all the operations with the car parked on the road outside my house, but it was summer. I replaced the heads with two from a local scrapyard which I stripped and rebuilt completely before fitting to the engine. There was no sign of obvious piston damage so I left the bottom end alone. I took 3 evenings to complete all the operations, finishing at 11:30 Friday night, and then competed at Gurston Down Hillclimb on the Saturday and Sunday.
First, drain the oil and water, disconnect the battery, remove the alternator, water pump, front timing cover, sump, and rocker covers. Remove the centre of the timing wheel from the camshaft.
Carefully get all traces of the broken nylon gear out of the sump, the timing cover, and any ledges within the engine. You don't want those little particles getting between the teeth of your nice new shiny steel wheel. Don't throw the pieces away yet, read the next paragraph first.
Remove any broken rockers fron the heads, and put them together to see if any jigsaw pieces are missing. If they are incomplete, the missing pieces must be recovered. They are probably in the camshaft gallery, but could be in the sump, or halfway down elsewhere in the engine. Look through the pieces of fibre wheel in case some of them are rocker fragments.
Using a straight-edge, see if any rocker studs have risen above their fellows. If so, the stud will need to be pinned back into the head. At this point, if you haven't already converted to lead-free, consider doing so, because the machine shop that fits the valve seat inserts can also press the rocker studs back in to position and pin them with scroll-pins.
Remove the inlet manifold and both heads, and inspect the piston crowns and valves for signs of heavy contact. If a piston crown shows any marks, crack-test in situ using the coloured aerosol dye kit. If in doubt, pull it out
If you're still looking for missing rocker pieces, lift out the cam followers. You might also need to remove the camshaft to fully inspect the oil drainways. If after all that you are still missing pieces of rocker, get under the car and look on top of the oil pump, and on top of each big-end bolt.
I would suggest that you dismantle all the valves, and look for any that are bent. As said before, having got this far, you might as well run the heads over to a machine shop for lead-free conversion, (or get an exchange set from one of your Scimitar parts dealers)
Now is also a good time to inspect and possibly change the core plugs.
You are now ready to fit the new steel timing wheel, the heads, replace the sump and timing cover, re-introduce all necessary liquids to the car, and drive off into the sunset.
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(Or, blind faith can let you down)
"My oil pressure drops away when I corner. I've checked the dipstick and there's plenty of oil"
I wonder if you've got the right dipstick ? My first Scimitar had a front-well sump, but I suspect someone had put a rear-well sump dipstick into the car.
Drain the oil into a clean container and check how many litres you have; and if less than 4.5, top up with fresh oil. Put this measured quantity back into the engine, and mark the dipstick at the new level.
If there was the correct amount of oil in the first place, or you added oil but the problem didn't go away, drain the oil (again), drop the sump, and take the oil strainer off. Look for cracks in the pipe, or see if the o-ring seal is perished where the pipe bolts on to the pump. Also check the oil pump bolts for tightness, just in case it's wobbling about.
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(or only works sometimes)
First, check your gearbox oil level, particularly if the overdrive is cutting out when you go uphill or round bends. If you're driving the car, and the overdrive starts acting up, turn the radio on and tune it to a VHF station, then see if you can hear crackling when flicking the switch on. If you do, I've usually found it to be a faulty switch, either dashboard or inhibitor, so you can now relax and stop worrying that the gearbox is about to sieze from lack of oil
Assuming you have enough oil, the next likely cause is electrical.
Jack up the back of the car and support on axle stands. Switch the ignition on, but do not start the car. Select 4th gear, then flick the overdrive switch on. You should hear a click as the solenoid activates. If you do, then the fault is within the overdrive itself, either in the solenoid valves, or the pump, or the pressure system. (Not an easy item to overhaul on the car). If you can't hear the click, put a test lamp or voltmeter on the bullet connector of the solenoid wire and check for the presence of volts.
Let's assume you have no volts at the far end of the circuit. Start with the dashboard switch. Remove it from the dash, and check that there is voltage at the feed side when the ignition is on. If not, look at the fusebox and trace the fault through from there. Check that the voltage comes and goes on the output side of the switch when flicked on and off. Replace if faulty
Now comes the dirty part. Leave the ignition on, the car in 4th, and the dashboard switch on. Check under the car that you have volts on the input feed to the inhibitor switch, and volts out from it when in 4th gear. For intermittent faults, see if the volts remain constant when wiggling the gear lever, and check also for stability when in 3rd.
There really isn't anything else after the inhibitor switch to check, except for the bullet connector linking it to the solenoid.
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