Help needed to try shifting cylinder head bolts.

Hi

I am trying to get a cylinder head off a Range Rover V8. The heads are bolted through into the alloy block with steel bolts Loctited in. I am unable to shift several of the bolts - those that I have got loose I have used a 5/8" socket mated to a four foot long extension bar - just gently increasing the torque until the threads have let go with a 'bang'.

I am reluctant to increase the pressure on the sticking bolts as I fear that they may sheer off - heat has had no effect, any other suggestions??

Graeme

Reply to
Graeme
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All you can do is increase the pressure, if necessary the bolt heads will shear. Once all the bolt heads are off then it may be possible to slide the head off the studs, mole grips and heat and release fluid will get the remains out. OR: Do you need a replacement 3.9 engine? I have a perfect one from a cruncher that I bought for a project. 250 pounds, no offers buyer collects in essex or delivery possible by negotiation.

MrCheerful

Reply to
MrCheerful

Had this problem before, with alloy head and steel bolts. Alloy and steel together can trigger sacrificial corrosion, where the alloy corrodes onto the steel, which is preventing the head bolts turning. The Loctite is just adding to the problem. Sharp impacts to the bolt heads may help, but I think it's just brute force that will shift them. If the heads snap off, there are acids that will eat the corrosion away, but I can't remember which. Using shock to move the bolts will work better than gently increased force.

Reply to
r

Hi - thanks for the advice, I'm going to get a 5/8" wall socket tomorrow and give it a go with that.

Not in the market for a 3.9 but, you could try a post on the newsgroup alt.fan.landrover - maybe somebody there interested

Reply to
Graeme

Impact driver?? Would that help??

Graeme

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Reply to
Graeme

It should be Scotchclad 776 rather than Loctite, but it's a similar thing.

They do go with a bang, but there's no chance of shearing them. The threads in the block go long before the bolts if you try overtightening them, so the bolts are pretty tough.

On some of the bolts, it could be you're jamming the socket up against the wall of the chamber which would increase the friction. Try undoing from the opposite side of the engine.

I've had the heads off many of these and never used anything bigger than a

2ft breaker bar - and managed ok with an ordinary socket ratchet before I got this.
Reply to
Dave Plowman

Borrow or hire a powered impact wrench, or tow the car around to a place that has compressed air drills (like ATS that almost weld your wheels to the hubs). DaveK.

Reply to
DaveK

This is why the factory specify (or did) Scotchguard 776. It seals bolts which go into the water jacket, prevents any corrosion, lubricates them so you get the correct torque and locks then against vibration etc. It comes in litre tins at about 30 quid, but a tin lasts a very long time and can be used for any bolt etc to prevent corrosion and to lock it. It's a small price to pay for preventing snapped bolts, etc. I had some trouble getting some recently, but got the address of a supplier from 3Ms. It's mainly used in the aircraft industry.

*Proper* Rover dealers used to stock it. ;-)
Reply to
Dave Plowman

Being a hydraulic mechanic, I have some experience with things being locktited in. Being alum will make it a bit more sensitive, but this is THE best way to get locktited bolts free. You will need to use the good old blue tip wrench, aka flame wrench, aka a torch. If you have a Acetylene torch that works or a normal propane torch will work. The key is LOW (for these type of torches) heat. You will want to gradually heat the area around the locktited fastener where it is locktited. You are not trying to heat the fastener, but the metal around it. Normally you will be able to smell when the locktite gets hot and melts, but being as how they are sealed between the head and block you may not be able to smell when it gets hot enough, but it will have to get pretty hot to release the locktite.

One word of caution would be that it could make high/low spots on the block which will require possible facing by a machinist, so keep that in mind. I normally do it with cast iron/steel, alum may need to get hotter on the outside due to it's heat dissipation properties, which could cause issues.

Larry

-----Original Message----- From: snipped-for-privacy@autox.team.net [mailto: snipped-for-privacy@autox.team.net]On Behalf Of Pete Bronlund Sent: Sunday, November 16, 2003 9:46 AM To: snipped-for-privacy@autox.team.net Subject: Fw: Help needed to try shifting cylinder head bolts.

Can anyone help this Gent?

----- Original Message ----- From: "Graeme" Newsgroups: uk.rec.cars.maintenance Sent: Monday, November 17, 2003 6:23 AM Subject: Help needed to try shifting cylinder head bolts.

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Reply to
Pete

How drastic do you want to get? I've had successes in similar situations using an old arc welder - connect earth to the block, then short (no arc) to the bolt head so the current flows to the block through the bolt thread but doesn't melt anything. Then spray with penetrating oil while hot, and leave to cool down before unscrewing. Apparently the greatest resistance to the current is the corroded interface between steel & alloy, so it gets hottest & breaks down leaving a space. Then the oil gets drawn in as it cools. But only use as a last resort - I've haven't had any problems, but you takes your chances . . . For future reference, it's easier to undo steel bolts in alloy when the engine's hot. When assembling engines, I always use Red Hermetite as a sealant on all threads to stop water getting in & causing corrosion.

HTH, Dave

Reply to
Dave

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