4.8 Valve clearance adjustment

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Craig Lord
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4.8 Valve clearance adjustment

Post by Craig Lord »

Howzit guys

Want to get the valve clearances checked on the patrol so I contacted my local dealer for a quote. They are insisting that in order to get new shims put in they have to take the head off and send it to engineering.

I'm no mechanic but I'm almost 100% certain that you dont have to take the head off, in fact you dont even have to take the cam shafts out if you have the right tools do you? You shouldnt need to touch the head at all?

They say that if the shims need to be grinded to a different thickness then the engineering needs the whole head to do this. But surely you just take the shims themselves to engineering and provide them with the measurements that you require?

Can anyone provide some clarity?

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Dungbeetle
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Re: 4.8 Valve clearance adjustment

Post by Dungbeetle »

Whoever you spoke to has one of the following problems

1- He has no idea

2-They do not have shims in stock / do not know where to get (Nissan does not sell them, they reuse from a special kit)
Maybe this is why they have an (under the tree) plan to remove the top and send it somewhere

There is no need to take off the top to adjust clearance - it can be easily done in situ (if that is the only problem....)

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Re: 4.8 Valve clearance adjustment

Post by Craig Lord »

Thanks Rudolf, I thought as much. Will have to wait for the borders to open so I can take it to someone in SA.
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Peter Connan
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Re: 4.8 Valve clearance adjustment

Post by Peter Connan »

I am not an expert on this, but my logic indicates that, if the shimming is out, one would need thicker shims, not thinner ones. Thus, one can't just grind the existing ones...

Have you tried a thinner oil yet, before getting into a flat spin?
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Re: 4.8 Valve clearance adjustment

Post by Craig Lord »

Hi Peter, I'm definitely going to try a thinner oil yes I was just interested in getting a quote from them just incase it didnt work and was surprised by them saying the head would need to come off... as for whether the shims would need to be thicker or thinner I'm not sure but logically i would also think thicker...

For those that are interested here is what the Haynes manual says about valve clearances and adjustments for the 4.8..

13 Valve clearances
TB48DE and ZD30DDTi engines

1 Checking the valve clearances is not a difficult procedure, however the adjusting procedure can be extremely awkward without the special Nissan service tools, especially if more than a couple of valves require adjustment. If valves of this type have not been adjusted by you before, it is recommended that the tools be obtained or the vehicle be referred to an authorised dealer or a specialist workshop, that has the service tools. The Nissan part No. for the tools required are KV 10115110 and KV 10115120.

To check and adjust
The valve clearances are adjusted with the engine cold.

2 Remove the rocker cover (see Chapter 2 Petrol models , or Diesel models ).

3 Using a socket and bar, rotate the crankshaft clockwise, until the mark on the crankshaft pulley is aligned with the mark on the crankshaft position sensor bracket. In this position the cam followers of No 1 cylinder are loose. If necessary, rotate the crankshaft one revolution until the cam followers are as described.

4 On the TB48DE engine, using feeler gauges, measure the clearance between the cam follower shim and the cam lobe on the following valves: No 1 cylinder inlet and exhaust, No 2 cylinder inlet, No 3 cylinder exhaust, No 4 cylinder inlet, No 5 cylinder exhaust. Record the clearances for future reference.

5 Rotate the engine one revolution clockwise and align the timing marks as described in step 2.

6 On the TB48DE engine, using feeler gauges, measure the clearance between the cam follower shim and the cam lobe on the following valves: No 2 cylinder exhaust, No 3 cylinder inlet, No 4 cylinder exhaust, No 5 cylinder inlet, No 6 cylinder inlet and exhaust,. Record the clearances for future reference.

Note:
In this position, the cam followers for No 4 cylinder will be tight, on the ZD30DDTI engine. On the TB48DE engine, the cam followers for No 6 cylinder will be tight.


7 If a valve clearance is outside Specifications on models with a shim, adjust the clearance using the following procedure:

Note:
If difficulty is experienced adjusting the valve clearances using the following procedure, it will be necessary to remove the camshafts (see Chapter 2 Petrol models , or Diesel models ). In some cases it may be necessary to remove the fuel return line.

Rotate the engine clockwise until the cam lobe of the valve requiring adjustment is uppermost.
Rotate the shim using the manufacturers special tool or a suitable size pin, until the hole of the shim is facing the side of the cylinder head.
Using the manufacturers special tool or with an assistant carefully using two screwdrivers to depress the cam follower, remove the shim from the top of the cam follower using a small magnetic screwdriver.
Measure the thickness of the shim using a micrometer and using the following formula, calculate the thickness of the shim required to restore the valve clearance to Specifications.
N = T+(A – 0.29 mm) — (TB48DE engine; inlet valve)

N = T+(A – 0.33 mm) — (TB48DE engine; exhaust valve)

N = T+(A – 0.35 mm) — (ZD30DDTi engine)

N = Required shim thickness;

T = Original shim thickness;

A = Recorded valve clearance.

Shims are available in thicknesses increasing in increments of 0.02 mm or 0.05 mm, depending on the engine type.

Ensure that the rocker cover gasket is serviceable. If necessary, renew the gasket.

8 Apply a smear of Loctite Ultra grey or equivalent sealant to the front engine housing gasket face and over the timing chain cover and the cylinder head joint.

9 Install the rocker cover and any remaining components to the engine (see Chapter 2 Petrol models , or Diesel models ).


10 Start the engine, check the idle speed (see Section 10 ) and also check for oil leakage.
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Re: 4.8 Valve clearance adjustment

Post by Tinus lotz »

Dude om te meet is om te weet.... :mytwocents:
Flush your motor put clean oil thinner ones and see otherwise come visit anthony when borders open .... :oldtimer:

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Re: 4.8 Valve clearance adjustment

Post by Craig Lord »

100% will try the oil and see, have just ordered the new filter :thumbup: otherwise I will see you soon after borders open
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Re: 4.8 Valve clearance adjustment

Post by Peter Connan »

To be honest, that doesn't look too difficult (at least, it's reasonably easy to check if not to repair).

However it does confirm my suspicion that, if the clearances are greater than they should be, the shims can't just be ground. If the clearances are too small (IE if the valve seats have receded), they could be ground, but that wouldn't result in a tappet noise.

Also, mildly excessive clearances wouldn't really cause any short-term damage, so you can wait for the borders.
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Re: 4.8 Valve clearance adjustment

Post by Craig Lord »

I did some more reading on one of the other patrol forums re the grinding of shims. Apparently 2 main things can result in the need for doing this:

1) As you say Peter, if the valves have receded. This can be caused by long periods of strenuous driving where the engine is constantly under high loads and driving at high rpm for extended periods or by sitting on the limiter for too long and too often. The Aussies have to get their clearances checked every 20k km if they are running on LPG also. The valves are beaten into the head until there is no clearance left at all, this can cause the engine to run hot along with other damage. Apparently its normal to hear a slight tapping on startup as the valves seat but if you have no noise and a fluttery idle with an occasional misfire this can be a sign of receded valves or insufficient clearance. Apparently you can test this by holding a piece of cardboard over your exhaust, normally it should be forced away by the pressure of the escaping gasses but if it is occasionally "sucked" flush with the exhaust it might be an indication of this issue.

2) if you need to adjust the clearances but you cant get the specific sized shim that you need from the manufacturer. The shims come in sizes increasing in increments of 0.02mm or 0.05mm depending on the engine but you may find you need a size in between in which case you will need to grind the closest sized shim down to suit your needs.

It will be interesting to hear what the more mechanically minded guys think of the first point and what else could cause that issue.
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