Rover V8 ticks when warm

Zaphod · Post by **Zaphod** » Fri Nov 29, 2013 8:29 pm

I have a 4.0 V8 discovery which has an irritating tick when warm.

I am pretty sure it has had an overheating issue in the past as the temp gauge had been disabled (one of the gauge terminals had been unscrewed), however it does not overheat now.

When it is stone cold it the engine runs perfectly, as it warms up it is silent till after the stat has opened. Apart from the tap the engine seems fine, it does not overheat, loose water misfire, does not seem down on power. I have had similar on the old Honda 2.7 V6 which would be quiet and then rattle when warm, normally cleared by adjusting the exhaust rockers but obviously this is not an option on the rover V8 but can the rockers on this engine behave in the same way? totally silent when cold but rattle when hot?

kiwicar · Post by **kiwicar** » Fri Nov 29, 2013 9:11 pm

Hi
I would do the obvious checks for leaky exhaust gaskets, this type of leak can sound like a metallic ticking and come on as things heat up. If not then a dodgy tappet is a possibility on an older engine, as the oil thins as it warms up the tappet bleeds down and you get a rattle.
Best regards
Mike

ChrisJC · Post by **ChrisJC** » Sat Nov 30, 2013 7:04 pm

Chris.

Zaphod · Post by **Zaphod** » Wed Dec 04, 2013 8:16 am

I'm fairly sure its not the manifold gaskets, but only because the tap is there when using a stethoscope alothugh please correct me if this won't eliminate that posiblity!, athough I do think there may be an ever so slight issue there as on initial start up the engine quietens down after about half a minute to near silent (basically fan noise only) and not in the way that would indicate tappets adjusting!

One thing to add about the tap, it does not come on gradually as the engine warms up, it is like its just switched on at a certain temperature, and does not get any worse or better, just as the dash guage goes above the lower white mark on the temp guage

However the history as I know it. This engine has 75K miles on it, and has been run on LPG (zavoli multi point) sicnce 15K, and from removing one rocker cover appears to be cleaner insisde than outside, It would be ineterestiong to see how the cam and followers have faired, as I beleive they are normally dead at about this millage, I have a theory the main reason for this was the tendancy for the old head bolt arrangement to allow exhaust gasses into the valley thuis sludging it up, leading to excessive cam wear. This is a later engine missing the outer row, which should not suffer this, and having been run on LPG most of its life sludge should not be an issue and thus cam wear should be far less. We shall see!

ChrisJC · Post by **ChrisJC** » Wed Dec 04, 2013 10:02 pm

You could remove the rocker covers and use a DTI to measure the pushrod movement as you rotate the engine. That will give you an idea of whether the cam lobes are in-spec.

Chris.

mgbv8 · Post by **mgbv8** » Wed Dec 04, 2013 11:01 pm

ChrisJC wrote:You could remove the rocker covers and use a DTI to measure the pushrod movement as you rotate the engine. That will give you an idea of whether the cam lobes are in-spec.

Chris.

The problem with doing that is you cant guarantee that one or more lifters has not bled down a tad ?

If this has to be checked I would think about maybe getting messy and warming the engine until the noise happens and then remove the rocker covers and start it up. The noise may be more noticeable and you can apply some finger pressure to each too see if the noise changes on one of the rockers. (this should only be done if you are happy that you can do it safely)

I've done it many times over the years on old engines with worn tappets.

mgbv8 · Post by **mgbv8** » Wed Dec 04, 2013 11:05 pm

Do you have an oil pressure gauge on the engine or just an oil warning light?

Zaphod · Post by **Zaphod** » Thu Dec 05, 2013 11:20 am

I am afraid all I have is the idiot light at the moment. I do have an old dual guage from a sprite, was thinking about fitting it to have a real temp guage!

Unfortunatly taking the rocker cover off the later THOR motor is easier said than done, the upper inlet has two plenumns over the rocker covers and the heater pipe work also has to be removed before you can take the cover off, which means it would have to warm up with the cover off... very messy!

ChrisJC · Post by **ChrisJC** » Thu Dec 05, 2013 7:49 pm

mgbv8 wrote:
ChrisJC wrote:You could remove the rocker covers and use a DTI to measure the pushrod movement as you rotate the engine. That will give you an idea of whether the cam lobes are in-spec.

Chris.
The problem with doing that is you cant guarantee that one or more lifters has not bled down a tad ?

A good point. However, I have never managed to get a tappet to bleed down, even with them out of the engine and in a vice!!

Chris.

mgbv8 · Post by **mgbv8** » Thu Dec 05, 2013 8:35 pm

Zaphod wrote:I am afraid all I have is the idiot light at the moment. I do have an old dual guage from a sprite, was thinking about fitting it to have a real temp guage!

Unfortunatly taking the rocker cover off the later THOR motor is easier said than done, the upper inlet has two plenumns over the rocker covers and the heater pipe work also has to be removed before you can take the cover off, which means it would have to warm up with the cover off... very messy!

Ouch!!
Thats some heavy plumbing going on there!! I sometimes forget just how exposed my engine is with just one carb fitted

Zaphod · Post by **Zaphod** » Fri Dec 06, 2013 11:44 am

Oh bottom, I'm not sure if this is becuse it is slightly overfilled (About 2mm over max) or somthing more insidious but there is an oil leak that may be from the crank seal (The oil pump) or filter but hopfully the sump gasket.. and I have the top end in bits so can't use my normal cleaning method which is the local jetwash.. Actually the rocker gakets are also leaking. But I have also heard about the oil pump rotors breaking up on these engines but still making good oil pressure

I bought the disco from a friend (eyes wide open, no undisclosed issues) because of the 'tick' which was there when he bought it. He had the oil changed for 15w40 and its been over filled scince and it seemd to be oil tight before this.

DaviesDJ · Post by **DaviesDJ** » Sat Dec 07, 2013 8:15 am

Hate to raise the issue but a slipped liner and block crack has exactly these symptoms. Tick when warm, history of overheat, run on LPG etc. are the coolant hoses over pressurised when running? I,e do they feel harder then they should? Up to 60% of these blocks have that problem especially the later Thor types as they ran them deliberately hotter for e missions purposes (only way to keep them legal in the early 2000s). They almost all go in the end! But a top hat liner completely cures it - but this is expensive as we all know!

Zaphod · Post by **Zaphod** » Sat Dec 07, 2013 7:32 pm

It could be, but I am doubtful. There is no pressurization, not coolant loss and no overheating (but I am of no doubt it has at some time in the past dues to the tampering of the temp gauge) the 'tick' is also wrong for a slipping liner, I am pretty sure that would be at engine speed not 1/4 engine speed

However I have got the rocker shaft off that side and have made a discovery. It looked like the inserts for the push-rods are not steel as I thought but bronze with a hard plating (possibly chrome) as every one looked to be like this and worn though to the base metal in places although one was significantly worse than the others (worn from the centre hole to the other edge of the push-rod seat for a good 1/4 of the seat area)

Zaphod · Post by **Zaphod** » Sun Dec 08, 2013 9:58 am

Pretty sure I have a failed tappet. Got it all back together with rocker shaft assembly from another V8. Started it and let it warm up, and the tick came back. However where as previously the tick would just appear as though a switch had been flicked it gradually came in, and faded in and out while warming up, and then in amplitude once established till at full temp when steady, only thing I can attribute this to is rotation of the tappet? just wondering if the damage I found on the rockers had stopped it rotating?

DaveEFI · Post by **DaveEFI** » Sun Dec 08, 2013 11:39 am

Way I check for a noisy tappet is to insert a feeler gauge in each rocker in turn with the engine running. If the noise changes, you've found it.