After repairing my starter yesterday, I took my car for a drive. Noticed a tappet pinging noise while driving in traffic especially when engine is hot. The heat guage was normal (90°).
Also noticed it before at that temp.
Its Ok on low revs but pinging starts as soon as I floor it a bit.
When engine has cooled down, its fine no pinging especially in the mornings, only when engine is hot and when weather conditions are high which sometimes reaches up to an abient of 30°C to 40°C in my part of the world.
Any comments will be highly appreciated!!!!
Could it be the oil i'm using pehaps (Motul. 8100 - 10W60)
Metallic pinging noise when hot and under load could be pinking (pre-ignition). Does it coincide with buying petrol? Try adding some higher octane fuel, see if it goes away.
I'm assuming your thermostat is working correctly and not failed open, too, and that you aren't getting the "Motor control system failure" dash warning.
Dont know if thermostat is ok, but gonna have it checked out.
Had a diagnostic done on her when I repaired the starter and everything tested Ok, mechanuc reset all fault codes, but a fews days ago engine light came on and "motor control system failure" warning on dash
"Motor Control System Failure", "Go to Dealer" "Service Schedule.............etc etc reading on dash, came on after a week or so, after my Mech had done diagnostics during the starter repair, and engine light also stays on?????
Catalyst-safe octane boosters do exist, though I've never had to use one, and no idea what is available in SA. Google 'octane improver south africa' throws up some suggestions and reviews. But you might want to ask for further advice in the SA forum, to find out whether pinking is a common issue on your local fuel, and what the best solution is. South Africa - Alfa Romeo Forum
David's suggestion is the most likely thing.
Octane boosters are not a fix for the problem if it does turn out to be pinking. The engine has a knock sensor which should stop it happening anyhow.
Tappet noises are often related to dirty oil and sludge. Regular oil changes help. In American V8's we used to let them idle for 20 minutes with a 50/50 mixture of kerosene and oil to clean up sticking tappets. Because the oil mixture is thin you dont drive them, just let them idle so as not to damage bearings.
I've attached a comparison picture of two thermostats. Personally I believe the failed thermostat is often a symptom of exhaust restriction, which traps more heat in the motor.
That does not really makes sense, If more heat is in the motor, the thermostat will just be open more often for a bit longer than usual... the fan will kick in more often to keep it below 90... If you said the higher exhaust gas temperatures (due to restrictions) caused pinging (pre-detonation) then I'd be saying you might have a point...
Your latter comment is almost a given, you can feel the extra heat of the manifold when the cats are blocked.
In respect of my prior point though, I believe the thermostats are not cycling in the usual manner when the exhaust is heavily blocked, and eventually their closing mechanism fails from persistent heat stress.
I have cat less and free flow exhaust and I have had a thermostat go stuck open on me... OK I have to admit I have been doing some track days in the car... Still the water temp stay on 90 on the track
There is no diagnostic code for a stuck (failed) thermostat.
The simplest way to diagnose is draining the coolant into a tray and removing the thermostat. If it is cold enough to hold with bare hands, you should be able to fill up the large plastic end spout and the water will not leak away at all.
If it is OK like this, you place it in a saucepan of boiling water and after a few minutes lift it quickly out with pliers, you should be able to see the sealing disc has retracted and if you pour hot water in the end where previously it would not leak - this water should fall straight through.
If all checks out OK then use some sealant on the clean dry surfaces when refitting the thermostat. I like Threebond "Reddish-Brown" RTV sealant but that is personal choice. If you need a new thermostat I recommend the Fleabay sellers in Latvia, they are cheapest and delivery is about two weeks but check they have stock first.
Filter the coolant as you pour it back in, and do not refit the reservoir cap until the first time the cooling fans have come on and gone off again (do not drive the car, just stand idling with the bonnet open). Sometimes you need to wait until this stage before the last 600ml of coolant can be poured in, as it expels all the trapped air.
Exhaust is a bit harder to diagnose if you don't have familiarity, especially if the car in question is "new" to you. A typical feeling with badly blocked exhaust, is weak acceleration or failure to maintain an open road speed up hills.
Simplest test is temporary substitution with a manifold that has the cats removed and straight pipes put in their place, or the insides stripped out. A decent load on the motor - couple of passengers and a long steep hill on the motorway (this may be harder to find in your area), is a good test as the engine is working hard - lots of fuel being burned, lots of exhaust gas (by volume and speed) being pushed out. If the car really gets up and boogies compared to before, you know pretty quickly the exhaust was a problem.
You cannot just test by revving the motor - there is no load, very little fuel being burned and as a result not much volume of exhaust gas, so blockages are not sensed.
But I'm sceptical about cat problems causing pinking. Too much back pressure will strangle performance alright, but inability to clear exhaust fumes should - I would think - reduce combustion efficiency and temps.
Both cars I've had constricted cats in, have displayed elevated coolant temperatures when labouring against the exhaust blockage. These have been in "real world" situations, not contrived tests (one cat meltdown happened on a 2700km trip with loaded trailer on the back, it cost a small fortune in fuel as I was travelling backroads without adequate equipment to do an ad-hoc fix on the road, and it was out of business hours for the most part, too).
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