cj10jeeper
New member
From my perspective having been a lifelong tuner and modder of cars and been stripping and building all manner of engines for c50 years, I believe I can add, to this discussion but no intention of going into battle on my view.
My view is simple and in my mind clear and I'll make no quotes nor long/multiple attachments Let’s just assume we use a correct grade of oil and a well maintained engine.
Firstly as background my V6 with c60k sounds like a bag of nails on start-up, after 1 minute and well beyond oil pressure build up it still rattles like a bag of nails. Drive for 10-15 minutes (or longer on very cold days or very slow driving) and it’s silent and restarts silently every time until the next overnight stop and restart from cold. The process then restarts.
Our non-hydraulic cam engines generally rattle when cold. This is because the gap is set to a spec. at cold which allows for oil pressure and thermal expansion of many components to a ‘hot’ or operating spec. JLR give a cold spec but could have as easily given a hot spec. which actually garages like because it saves waiting hours for engines to cool..
Oil pressure will have an impact albeit minor as the thicknesses of films in so tiny. The major changes will be in increased component length such as valve stem length and cam lobes from thermal expansion (as has been posted and explained clearly by member Tel). Together this all allows the correct clearance when oil pressure is achieved and all components are up to full operating temperature.
Given oil reaches operating pressure in an engine in a few seconds especially in our engines being a very thin grade, it's impact on changing rattling would be very quick.
So if we start cold and the engine rattles, we run it for a few seconds and if the noise stops then we can reasonably assume it’s oil pressure that’s fixed the noise, since there will be no time for thermal expansion. If it continues to rattle for more than a few seconds, then it’s not oil pressure / lubrication related. The only other variables now are thermal expansion or excess wear. If after 5-10 minutes or more when the engine/climate is very cold, if the tapping stops then we are at the correct operating gap and the variable was thermal, nothing further to do with oil.
If it still continues to tap when hot then we may be looking at valve train wear and the need for adjustment or tracing other more serious wear issues in any of the valve train components, such as cam lobes or bucket wear.
My final ‘test’ would be get to the engine hot. Switch off for 15 minutes and restart. If it starts noisily then the reason can be linked to oil or wear, if it’s still silent then thermal expansion is the only factor as after this time oil will have mostly drained, but the engine still hot and components at full thermal expansion. That takes us back to my experience of my engine.
My view is simple and in my mind clear and I'll make no quotes nor long/multiple attachments Let’s just assume we use a correct grade of oil and a well maintained engine.
Firstly as background my V6 with c60k sounds like a bag of nails on start-up, after 1 minute and well beyond oil pressure build up it still rattles like a bag of nails. Drive for 10-15 minutes (or longer on very cold days or very slow driving) and it’s silent and restarts silently every time until the next overnight stop and restart from cold. The process then restarts.
Our non-hydraulic cam engines generally rattle when cold. This is because the gap is set to a spec. at cold which allows for oil pressure and thermal expansion of many components to a ‘hot’ or operating spec. JLR give a cold spec but could have as easily given a hot spec. which actually garages like because it saves waiting hours for engines to cool..
Oil pressure will have an impact albeit minor as the thicknesses of films in so tiny. The major changes will be in increased component length such as valve stem length and cam lobes from thermal expansion (as has been posted and explained clearly by member Tel). Together this all allows the correct clearance when oil pressure is achieved and all components are up to full operating temperature.
Given oil reaches operating pressure in an engine in a few seconds especially in our engines being a very thin grade, it's impact on changing rattling would be very quick.
So if we start cold and the engine rattles, we run it for a few seconds and if the noise stops then we can reasonably assume it’s oil pressure that’s fixed the noise, since there will be no time for thermal expansion. If it continues to rattle for more than a few seconds, then it’s not oil pressure / lubrication related. The only other variables now are thermal expansion or excess wear. If after 5-10 minutes or more when the engine/climate is very cold, if the tapping stops then we are at the correct operating gap and the variable was thermal, nothing further to do with oil.
If it still continues to tap when hot then we may be looking at valve train wear and the need for adjustment or tracing other more serious wear issues in any of the valve train components, such as cam lobes or bucket wear.
My final ‘test’ would be get to the engine hot. Switch off for 15 minutes and restart. If it starts noisily then the reason can be linked to oil or wear, if it’s still silent then thermal expansion is the only factor as after this time oil will have mostly drained, but the engine still hot and components at full thermal expansion. That takes us back to my experience of my engine.
