Slight Knocking on start up...

G

grifterkid

Member
I'm probably worrying a bit too much but when I start my 1974 P6B there is a the slightest rattle/knock... It only lasts for about all of 5-10 seconds and then it goes, no more knocking and normal service resumed. Should I be concerned...! The car has only done 70k miles and has been regularly serviced. Could I have lose tappets? It is having a full service in the new year... Any help/advice would be hugely appreciated...
 
Hello Ash,

A couple of questions to start with......does the oil warning light remain on while the knocking is evident? Are you running 20W-50 engine oil and if so which one is it?

My original 3.5 litre engine developed a slight knocking on start up, but only when hot. This was around 1988 with some 70,000 miles on the clock also. Up until that time I had been using Castrol GTX then GTX2 with changes every 2 to 2500 miles. I also noted that knocking would be evident on initial start up after having changed the oil filter. I changed brands, went to Pennzoil GT Performance which was also a 20W-50 oil. In both cases, the knocking would never return.

It might be a good idea to try a different brand of engine oil.

Ron.
 
Good advice from Ron there. Most likely source is the hydraulic tappets pumping up. A standard V8 feature and not susceptible to adjustment. If accompanied by persistent low oil pressure - ie less than 15psi at idling then there may be other things to look for. At worst you might have a worn cam lobe - checked by visual inspection of the rocker action with the cam covers off.

Chris
 
I've got good oil pressure both at idle and when running... I'm not sure what oil my mechanic put in at the last service so I shall check... What is the best oil to use (I'm sure I asked this on here before) for the V8 engine? As I mentioned it will be having a service in the next couple of weeks so should I advise my mechanic to check anything specific? As I said the engine still runs perfectly with no knocking when running and no loss of power. Maybe I'm just being paranoid, odd noises in old cars does that to me...!!!
 
Hello Ash,

Within the United Kingdom, Halfords 20W-50 appears to be very highly regarded by owners of Rover V8 powered vehicles. Here in Australia, Penrite is equally popular. With my 4.6 litre engine, I use Penrite HPR 30.
Which ever 20W-50 oil use settle on, it must have sufficient zinc and phosphoros (ZDDP) else your camshaft and tappets will wear away very quickly... :shock:

The ZDDP topic has been discussed previously, so take a walk through this section and you will find it.

Ron.
 
And don't forget that V8 wants much more regular oil changes than a modern car - all the experts recommend 3,000mls.

Chris
 
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