Replacing 300tdi Head (Warning - NEWB Alert!)

Was driving down the motorway today when coolant started ****ing out of the radiator. Engine had overheated without me realising, called an AA guy to get me home, and he's said the head gasket has gone.

I figured that seeing as I was going to have to take the head off and most likely get it skimmed, I may as well just put on a new head with new valves, springs etc and ultimately extend the life of the engine. I've also ordered a new water pump, thermostat and, although the water feature was amusing to passers by, a new radiator too.

Is there anything else that's worth replacing whilst I've got the head off. Piston rings? My sump has a big dent in it, should I replace that?

And now the newb bit - the last time I replaced a cylinder head was about 25 years ago on a 1.3 NA Vauxhall Nova. I remember having to line up cams and make markings on the engine so that when the cam belt was replaced the valves would be in time with the pistons. Looking through the Haynes manual, it doesn't say to do any of this, this confused me. Having a poke around in the engine, there are no cams on the cylinder head. wtf? Ahhh, it's not a DOHC. I thought pretty much all engines were DOHC so this is new to me. Am I right in thinking that the cam is under the head? Specifically, how do I ensure that all of the valves are in time when I replace the head? Does anybody have a link to a step by step guide with photos/video for the entire job?

Thanks in advance, I imagine I'll have more questions once I get started on the job.

It's not an ohc engine so timing is not disturbed. Easy job really.

Download "RAVE" ( search on here ) - it's the official manual and covers almost everything ...

IMHO it's a little better than the haynes "effort" too ....

Did the AA guy give you any other evidence that indicated to him that it was the head gasket causing the rad leak?
Where on the rad is it leaking? Is there any sign of damage or corrosion at that point?
I'd be tempted to buy a new rad (you've got to buy one anyway) and get some checks done to get a better idea if the gasket has failed or not.

To change the pistons rings you will need to disconnect the pistons from the crank and then you're in to running in new rings. Where is the dent in the sump? You might want to check it's not affecting the oil pick up. If it's not, then I wouldn't worry about it.

As has been said above the cam is in the block and there are cam followers and push rods which transmit the movement to the valves in the head.

The head bolts are re-usable a few times. But, for the cost of a new set, it might be worth getting new ones.

Don’t bin your old head, get I reconned as a spare.

Maybe while it’s in bits get your injectors serviced?

Old head is off. It was almost worryingly easy!

Rocker shaft is duff though. As you can see in the image below, there are pitting and deep grooves in the shaft.


A believe you're supposed to change the bushings in the rocker arms at the same time but I don't think I have the necessary tools to get them lined up properly so I'm just going to replace the lot. Looking at the existing rocker arms though, numbers 3 and 4 are different to all the others. For the most part they are stamped with part numbers ERR3342 and ERR3343. However, numbers 3 & 4 don't have these stamps and the actual arms themselves (the lever part, not the part that contains the bush) are slightly thinner than the others. I'm guessing somebody has replaced some of them and mismatched them. What are your thoughts? Ok to replace them with ERR3342 and ERR3343?



As I was stripping the shaft, my missus decided it would be a good time to have an argument and I managed to botch the sequence as I was taking the rocker arms off. I have the arms in the correct order, but I'm not sure about the spacers/washers. Any advice?

Is it possible to buy the full shaft as an assembly with all of the arms/springs etc ready to drop in?

Is it worth changing the push rods whilst I'm at it?

After all of this is done, will the engine need running in?

Will have a look at the cam followers / tappet assemblies tomorrow and see if they need replacing.

As an aside, I knew that with petrol engines you could tell a lot about how the engine is running by inspecting the spark plugs. I wondered if this was the same case with glow plugs. As I pulled them out of the head it became glaringly obvious:


And for completeness, a photo of the block with the head removed:


Will respond to previous comments in a separate post.

Al2O3 said:

Did the AA guy give you any other evidence that indicated to him that it was the head gasket causing the rad leak?

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I was driving down the dual carriage way and I thought it was raining. I had my window wipers going but then I noticed that nobody else did. Water was ****ing out the front of the rad. The AA guy put some radweld in and it slowed the leak down enough for me to drive home (wasn't far). Don't know how he diagnosed the head gasket. He put his hand of the water expansion tank and said head gasket. As a fellow Defender owner, I took his word for it. Looking at the condition of the glow plugs I took out (see previous post), I'd say he was right.

Al2O3 said:

To change the pistons rings you will need to disconnect the pistons from the crank and then you're in to running in new rings.

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The bores look really clean so I think I'll leave alone and get the car back on the road (daily driver).

Al2O3 said:

Where is the dent in the sump? You might want to check it's not affecting the oil pick up. If it's not, then I wouldn't worry about it.

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Cool. Thanks. Will look into it.

Al2O3 said:

The head bolts are re-usable a few times. But, for the cost of a new set, it might be worth getting new ones.

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Somebody has painted a number 1 on the head bolts but that doesn't mean anything. I don't need to worry about it though as the new head came with new bolts.

flat said:

Don’t bin your old head, get I reconned as a spare.

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Good idea.

flat said:

Maybe while it’s in bits get your injectors serviced?

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I looked at the price of new ones. Sod that! What's the process for getting them serviced?

You can buy the individual parts for your rocker assembly at Turner's or somewhere similar.
Turner's https://www.turnerengineering.co.uk/PBSCCatalog.asp

You can get reconditioned ones like these. LINKY
I got a similar set, but didn't have to put mine in part-ex.

No 1 painted on head bolts is for tightening sequence, angle tightened, not torque tighten

Useful video here for stripping down and cleaning injectors: