Discovery 300Tdi Head Gasket Queries

Hello chaps - my first thread in this section!
A couple of days ago my old dad bought himself a 1994 300 Tdi Discovery Auto off of eBay for what he thought was a bargain price, but upon bringing it home to show it to me I noticed a hissing/puffing noise coming from the rear of the engine, and putting my hand down behind the head confirmed my fears, it seems the head gasket is blowing from the rearmost cylinder.

Luckily, the oil and coolant don't seem to be mixing and there are no signs of overheating at all, so it looks as though it has only blown in that one place.

So it looks like I'll be changing the gasket for him. I've got a couple of questions though, firstly, in this case where the engine doesn't seem to have overheated and the oil/coolant aren't mixing, will the head require skimming?

Secondly, there appear to be three or four different versions of the gasket available for the 300Tdi, how can I tell which one I need? And is it worth saving £20 and going for a pattern part, or should I use a genuine one?

Thanks all
Langers

Hard to say what the head will need without inspecting the face.You need to clean up both faces,block and head,taking note of all marks and stains between the openings as you go.If you have a decent straight edge,once you have cleaned the muck off with a nylon scouring pad and paraffin,check for flatness.Look for visible signs around the bores of gas escape,sort of little sprays outwards.Theres lots on here if you search but if you arent confident,get it checked and then skimmed if necessary.The block face needs to be cleaned shiny but dont use anything that you dont want flowing round your engine later,like wirewool.Stick to nylon scouring pads.Have a good look at the bores while you are in there,and the piston crowns.

Most people go for the three of even four hole gaskets on older engines as they are more forgiving of slight faults,as are composite gaskets like Elrings.The MLS,multi layer shim gaskets,in my opinion are great with perfect heads and blocks but can be less forgiving of slight faults than a composite.Again,there is a mass of info on here....much of it my misadventures in head and gasket land.....so do an (admittedly tedious) search,or a load of them with every wording you can think of.

The book says that headbolts can be used a maximum of 5 times....unless you know how many times they have been used before,get new ones or you will be kicking yourself for not spending the 20 something quid when it goes wrong.I was given a great bit of advice on here recently on the tricky angle-tightening that the head bolts need after torque-ing - that is that since the angle required is 60 degrees then mark the bolt and head and turn it one flat.Saved me a lot of bother on the hard to reach rear bolts.The 20 deg is easily done by marking a third of a flat.

Thats all I can think of for now....wiser heads will chip in with more and better soon enough ! Oh,one thing that can save you some real embuggerance....the rear headbolts - there isnt really room to drop them in with the head in situ so place them in the holes in the head without any hanging below and tape them up with some masking tape,then let them drop once the head is slotted into place.

That and search,search,search ! Good luck mate !

i got a feeling when the head bolts are released it,ll want skimming go for the no-holer gasket as its thicker thus once the head has been skimmed , if you use a standard gasket the valves may well hit ............. take all the valves and springs out first mind before getting it skimmed assumming it,ll need doing it will save a few quid , gasket sets on ebay for £20 inc valve stem seals inlet gaskets all the bits you need

Count the holes when head gasket removed - most likely 3 hole and if in doubt fit 1.6.

Note the stretch bolts need replacing and two bolts at back are a pain re fitting as are the breather hose brackets. You will need torque wrench and angle gauge.
Crack test,skim to be sure

I have got a straight edge in the shed somewhere. I think I will wait until I remove the head before buying the gasket - at £40 it would be a pain to get the wrong one.

Not knowing how long it has been driven in this condition, I'm not sure what the condition of the mating faces will be in, but as I said it doesn't overheat and runs spot-on aside from the hissing noise. It managed the 120 mile drive back home without fault, so fingers crossed it'll just want a good clean up and a new gasket.

Rest assured a certain eBayer will receive a scorning negative feedback once I confirm my suspicions.

Thanks for the replies all, I'll update with pictures at some point next week.

they usually bend in centre part of head ifaround or less than 2 thou and no fire ring marks you can refit ,if its very warped renew as may lift again if head stresses have relaxed,very rare for them to blow to put water in oil usualy between cylinders and to water way,if not skimmed you fit whichever gasket was fitted before 1,2,3 hole stamped through gasket on drivers side rear of middle seen with head on,3 hole if unsure,you can use the fact that bolt head has 60 degrees per flat to tighten bolts easier than angle guage,better to fit dowels to head to hold gasket often stay with head,worth getting new as often break ,you can leave turbo connected and just undo manifold nuts and pull away while removing / refitting,check ex/in manifold gasket for blowing before actually removing head

jamesmartin said:

check ex/in manifold gasket for blowing before actually removing head

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I felt around the back of the head and can feel pulses of air coming from between the head and block, so pretty certain it's that. I did think it might be an exhaust manifold leak but I'm certain it's the head gasket now after feeling it.

its a known weakspot for 300tdi's get the head skimmed while its of.. good luck

Yeah probably best to get it tested while it's off. He's intending on keeping it long-term as a workhorse, so it would be good to have peace of mind.

The thing is, aside from this problem it seems like a really decent and solid Disco, all the usual rust areas are in perfect condition, it has 12 months MOT on it and he didn't pay much for it so I think it is worth the effort.

If you are reasonably fit,well equipped and located,it can be a weekend job.When I was young it was a two a day....but those times are long past.One of mine has taken over six months.Admittedly I did the head three times in a week before that (all failed) so I became a bit disheartened.Then again my P reg 300 has had the engine out for over 2 years now and not much closer to having back in.My father did manage to lose,yeas LOSE the engine for one of those years though.But thats another story............

if you really wat to do good job replace head with new ,skimming gives flat surface on a piece of ali thats bent due too heat ,this heat can also relax tension in head allowing it to move again and or loosen the tension on valve seats etc which are held in by been 3 thou ish bigger than hole they sit in ,skimming dosent fix a head its just pot luck whether it will last in long run,skimming a flat head is different than skimming a bent one in the chance of long term fix

jamesmartin said:

if you really wat to do good job replace head with new ,skimming gives flat surface on a piece of ali thats bent due too heat ,this heat can also relax tension in head allowing it to move again and or loosen the tension on valve seats etc which are held in by been 3 thou ish bigger than hole they sit in ,skimming dosent fix a head its just pot luck whether it will last in long run,skimming a flat head is different than skimming a bent one in the chance of long term fix

Click to expand...

Do you think it will be warped then? Even if it's not overheated or anything?
I'm hoping it's just the gasket that has 'perished' over the last 17 odd years. I will check the head for warping but I am hoping that it'll be OK.

no not necessarily heat bends heads ,flat head with marks ie around edge of bore etc(fire ring marks) can be skimmed with a knowledge that it should last,if no marks and flat just clean up ,i would think that 17 years was good age to last so i hope your not unlucky ,

I've got a 300 going into my dad's 90 soon, would it be worth doing the HG even though it hasn't gone for piece of mind or just leave it? Only contemplating doing it as the engines out.

Sorry to hijack aswell

I think if it's running well and not showing any signs of failure, I'd just be tempted to leave it be. Fit it as is, if it does fail at some point it's not too difficult to change the gasket with the engine in situ. Good luck with the engine swap, I did my 110 with a 200 transplant last summer, best upgrade I've ever done.

Just did my head gasket on Elmer 3 weeks ago, as oil was coming out of the O/S whilst running

advice I got from here and other land rover engineers was

Use OE head gasket
other gaskets are ok with after market
New bolts

from experience ensure you torque wrench is reading accuratley BEFORE doing up the head bolts

skim it whilst its off, may only need a small amout to provide a proper finish, but you can guarantee a good face

you can tell how many holes by looking at existing gasket protrusion below and slightly behind no 3 injector pipe


and to answer
"I've got a 300 going into my dad's 90 soon, would it be worth doing the HG even though it hasn't gone for piece of mind or just leave it? Only contemplating doing it as the engines out."

if the engine has done over 100k it may be worth doing for peace of mind. as its out
but its easy enough to do when the engines in, so not something I would do just for the sake of it

Might be worth getting the head pressure tested while its being skimmed too, better safe than sorry as I found out after having mine skimmed and buying new gaskets and refitting then finding out it was fooked! lol

And agreed, OE gasket, new bolts, follow the correct torque then angle.

My tip is to have a fat elastic band to hand to hold the two back bolts together when lifting the head off and re-fitting. And for what they cost, get a set of valve top caps.

Thanks for the advice all - got the head off yesterday with the help of a mate, did it in record time and done it all properly. Only broke two tools as well!

Anyway, here's what the gasket looks like, you can see it was blowing exactly where I thought it was - right at the back.





And here's the head itself after a quick clean up;







I have had a good look at the head and verified with my straight edge that it doesn't appear to be warped to any large degree

Just need to wait for my gaskets to arrive now (2 hole) and then put it all back together.

Is that a genuine LR head or aftermarket? I have found the genuines better,suprise surprise.You appear to have the same problem there as the one I just had skimmed,gas blowout at the back of No4.Mine was also an elring gasket,like yours looks to be.

I would be scrubbing that TOTALLY clean with nylon scourer sponges and paraffin and then dry polishing it ,with a very light touch,with a buffing wheel on a drill.THEM you could see if there was any pitting from the fire blowthrough at the back.Then similar clean of the block face,drain water and oil after to flush out any nasties that have dropped down the cavities.A good rule is to never clean the block with anything that would do damage circulating round a running engine,so no wire wool,wire brushes or hard metal scrapers.
Use brake cleaning fluid or similar solvent to clean head and block before assembly,and let it evapourate before.Everything else has been up on here recently,new bolts etc.

Why a 2 hole replacement gasket,by the way?