My 1990 toyota 2.8 pickup ( african import) got low on oil without indication and i thought had seized. got it back to the garage and sorted out pipe ,oil indicator and refilled with oil. It started up and runs fine apart from it now knocks realy bad on start up and continues constantly. what is the problem and can i fix it please help. Gary ( England)

Don't drive it! If it's flashing because you have low oil pressure you will damage the engine. The oil could be low, the oil pump may have failed or the oil.pickup filter in the sump may be clogged so it's not picking up oil. The fact that it's jumping means it may seize if it's not already damaged.

It sounds like the oil pressure is low. If the car has high mileage, this may be either a failed oil pump or a clogged oil pickup, or may be a clogged oil filter. You will need to drop the oil pan and see what is happening. IMPORTANT: If you attempt to drive the vehicle with a low oil pressure condition, the engine may seize, rendering the reason for the low oil pressure academic.

could be a wheel bearing

Try with the small stuff first. Replace the thermostat. Before you do that, you should flush and refill your system with just water after the flush process. The bottle of solution that you put into your radiator to flush it and clean it has instructions, follow those. Then let the car cool down and drain the system and refill it with fresh water only. Run this water for a bit and then do it once more. Once cooled back down , replace thermostat and replace the 50/50 mix of antifreeze and water.
Check engine oil level as well, low oil will overheat engines quickly.
NEVER REMOVE THE RADIATOR CAP ON A HOT ENGINE. !
NEVER REMOVE THE RADIATOR CAP ON A HOT ENGINE. !!
NEVER REMOVE THE RADIATOR CAP ON A HOT ENGINE. !!!

When was last oil change? I'd start there with a good 10w-40 wt oil and filter.

change the pcv valve

Best thing to do is have an cooling system pressure test done, this way you will know for sure where and if it is leaking, could be rear block freeze plug, but with test you will know for sure.

depends what engine you have, get model # and when you get your oil at auto parts, tell them what you have and they'll give you the right amount & proper filter

Probably cheaper to get a rebuilt engine. Approx 2 to 3 K.

check to see if alternator is working usually when light comes on alt has failed check oil level if level okay poss bad oil level sensor or wiring