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  #1 (permalink)  
Old 30th May 2006, 01:51 PM
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V8 Head Gasket Tips and Tricks?

Hi All,

In a day or two I'd like to replace the head gaskets on my disco as they are starting to weep externally. I've bought all the gaskets and some gasket glue but I was just wondering if there's anything I should be aware of or any special tools I need before starting the project?

I've bought one of the disco CDs off this site and as far as I can tell it's a pretty straight forward job of removing rocker covers, rockers etc and then the head bolts. From what I could tell none of the timing gear needs to be touched. Is this correct?

The engine in my disco is the 4.6L rangie engine and whilst my manual doesn't cover the torque settings on the 4.6L I'm guessing the head torque should be the same as the 3.9L. Is this a bad guess?

Any advice would be appreciated.

Cheers,

Harvs
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Old 30th May 2006, 02:23 PM
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get some wet and dry sandpaper to clean the block and head surfaces
and when you pull parts off such as push rods cam followers etc keep them in order so everything goes back the same.

Not sure about the bolt torque but do not assume it is the same someone on here will have the answer also be carefull about putting sealant on headgasket surfaces not allways a good idea I have pulled heads off and found some idiot has used silicone sealer
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Old 30th May 2006, 03:19 PM
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Quote:
Originally Posted by stevo
get some wet and dry sandpaper to clean the block and head surfaces
and when you pull parts off such as push rods cam followers etc keep them in order so everything goes back the same.

Not sure about the bolt torque but do not assume it is the same someone on here will have the answer also be carefull about putting sealant on headgasket surfaces not allways a good idea I have pulled heads off and found some idiot has used silicone sealer

Thanks Stevo,

I was a little hesitant about sanding the head and block. I was planning on just getting a plastic scraper and chipping off any residue and then cleaning the rest with a bit of metho/petrol. The engine was brand new when the previous owner put it in and this is the first head gasket change so I'm hoping there wont be too much to clean up. If I do have to use wet and dry rub what grade would you recommend?

As for the sealer, I bought some head gasket sealant from a landrover wrecker here in SA. They said it was suitable so I'm just going on that. One question I do have is how much do I use? I was planning to run a small bead of sealant around every metal part that the gasket touches. ie a bead on both the block and the head. Oh and I was going to do it in the following order.

1. Run sealant around block and let it sit for 5mins etc.
2. Press on the gasket.
3. Run sealant around the head let it sit.
4. Put the head back on and start torquing it up.

Does this seem reasonable?

Sorry for all the questions, but I want to make sure I do it right the first time round.

Cheers,

Harvs
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Old 30th May 2006, 03:27 PM
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are you sure the heads are flat? this can cause the weeping in the first place... you can have the machining done for (relatively) few dollars compared to having someone do the whole job.

Torque wrench settings vary from motor to motor - make sure you use the right settings for the specific motor and make sure you re-torque it and change the oil and filters (if water got into the oil) and flush the radiator again (if oil got in the water) after a week or two as the gasket beds in. nothing worse than doing the hard work and being too busy to re tighten the head bolts.... then the head gasket blows again and you are back to square one...yeah , I've been there and done that on my first car...
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Old 31st May 2006, 02:40 AM
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I used 800 grit then finished off with 1200,scotch bright is a good idea as well,the torque and yeild method does not need redoing as the chance of breaking bolts is high and replace your head bolts,I did mine (td5) the old bolts had stretched about 0.40mm so reusing these would cause them to break.

You can buy the torqgue(delete button on computer has stopped working so can't delete spelling mistakes) torque guage at super cheap ($25)
and as PLR has pointed out read and reread the manual
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Old 31st May 2006, 06:03 AM
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It's been a while since I did a V8 but here goes...

The head bolts are put in with thread lock... Make sure you clean the threads out.
When cleaning all the old crud off the block & heads, I usually just use a razor blade.
When the heads are off, check that they'll flat by using a flat edge.
The inlet manifold comes off as one unit but can be a sod trying to get it out of the way. I usually undo the injector connectors, etc... but others I know just tie the whole lot off to one side. Just do whatever works for you.
The only bit I've found to be fiddly is getting the valley gasket seated before fixing everything else over the top. The rubber bits at either end can be a bit of a sod sometimes.

It's not too difficult a job assumimg you don't hit problems... My biggest problem was snapping a head bolt while removing one of the heads. It was one of the lower bolts towards the back of the engine and it snapped off inside the block. I was sh1tting myself while we were drilling it out!!!

M
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Old 31st May 2006, 01:59 PM
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Thanks guys,

Sorry for the late reply, I've been running around trying to work out what's what and whether or not I should still be doing this job myself. But what the heck what's the worst that could happen? ....... Actually don't answer that.

PLR, the gaskets that I've got are some graphite flex gaskets from Durapro (some japanese company) model number GSBR290D if that helps. There doesn't seem to be any built in sealant bead so I'm guessing these are to replace the factory tin gaskets.

The engine number prefix as best as I can tell is 'S' however it could be a 8 5 or 6. Doesn't look like a B though. As for the ratio number I'm not sure what that is but there is a stamp of GR8.37:1 if that helps.

The other gaskets I have are the two little rubber gaskets and a large U shaped gasket (I'm guessing this is the valley gasket).

As yet I don't have any replacement head bolts so I'll have to head out on the weekend for a set of these.

Ok, so far I have this.

1. Head bolts aren't reusable so get some new ones
2. Clean out the threads
3. Clean surfaces with scotch guard (wet rub just scares me)
4. Check for a warped head with a straight edge
5. No sealant should be used on the actual head gasket.
6. torque settings are done once as per the manual ie. Torque to the specific Nm then via degrees for the rest.
7. Read the manual again and again
8. If a head bolt snaps put the disco on a trailer and take it to a professional

One questions that still remain is where does the gasket goo go then? The manual doesn't seem to mention applying goo at any point in time. Actually I've found it quite vague in the whole engine overhaul section. Am I looking in the wrong spot or does it just assume I know what I'm doing. It gives details about the head gasket torque settings, but I've found no details at all on the fitting of the valley gasket etc. All it has is an exploded diagram to show where things go.

Another question I have is, are the exhaust gaskets reusable? I don't have any new ones lying around so I might need to get some at the same time as the head bolts.

Once again thanks for all the help,

Harvs
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Old 1st June 2006, 05:30 PM
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Thanks for that Peter,

I think I've at least got enough info now to start the job and see where it takes me. I had assumed it was a 4.6 head but after that info, I chased up the mechanic who put the engine in and it was actually the 3.9 head bolted onto the 4.6. Now at least I know what I'm dealing with. As for whether or not the bolts are reusable I guess I'll just have to wait and see.

Cheers again,

Harvs,
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Old 1st June 2006, 08:15 PM
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Regardless you should not use "Gasket goo" on the gasket, and it says this in the manual
The sealant on the gasket from new should be just a thin blue or maybe red line around the water holes.
The sealant recommended by Rover is "Hylomar Blue" You can get it in a spray can or tube. You can spray it safely on the area where the head joins the manifold. I suggest spray it on the gasket, and a bit around the water holes at the front and back of the head. As it dries beefore you do things up it does not squeeze everywhere like silastic.
You are only supposed to use sealant (silastic)at the very ends of the rubber gaskets under the valley gasket, where they touch the heads. I have never had a leak through these unless the head gasket is pressurising the crankcase.Its a bit tricky doing up the bolts which hold the steel ends onto the valley gasket. they should only be finally tightened after the valley gasket has been torqued at the head faces
Tip- The valley gasket has "Front" on it. Put that to the front. Trust me.
Regards Philip A
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Old 1st June 2006, 08:41 PM
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V8 Engine Overhaul Manual for anyone?

Thought you might need the manal to complete the job. Please see the attached pdf file. I think that have attached it correctly, let me know if you have a problem. Good information about rover V8 can also be found at http://rpiv8.com

I have replaced head gaskets several times. Always used new bolts with only a little engine oil for lubrication. Head gaskets go straight on without any sealer.

Good luck

V8OHM.pdf
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