Seized Nuts

[epipete]

This is a general query from an engineering Luddite directed to the skilled fraternity out there.

Having sheared my third bolt today (this follows the two on the Exhaust Manifold), this one being one of the two bolts securing the Thermostat Housing, what is the best process for releasing these 20 odd year old fastenings?

Currently, I am soaking in WD40, giving the bolt head a judicious tap, turning my socket and 'ping' off shears the head

Advice please.

Pete

[GeoffSmith]

Penetrating oil not WD40.

[epipete]

Penetrating oil not WD40.

Thanks Geoff, I thought WD40 was penetrating oil. I'll try something different tomorrow surely it can't be that simple?

[Brit-Car-Nut]

Although WD40 claims to be a penetrant, it is barely useful. A true pennetrating oil will help especially on nuts that won't come off bolts and studs. The pennetrant needss to reach the threads that are seized so squirting the head of a bolt won't give much help. Careful heat at the thread end will possibly help.

I assume you mean the bolts that hold the thermostat cover to the thermostat housing?

Now that the bolt heads have sheared, is the shaft of the bolt still sticking out of the thermostat housing?

If you were taking the entire housing off the head, did the bolt shafts stay behind?

Soaking the thread end of the shafts so the penetrant gets into the threads will help. Be careful if it is the housing ears you are working with as the ears are fragile and can break if you are not careful to avoid twisting other than concentrically. The housing can be removed and the housing set in a vice so you can get access to the threads with some heat is also useful.

IF the bolts sheared flush in the head, using a center punch to get a good start, start small and carefully drill larger and larger holes until you can get a non-expanding EZ-Out to fit (at least 50% of bolt diameter). Make sure you don't drill off center and damage the threads in the head as you drill with bigger and bigger bits. Left hand bits really work well and often walk the remains out while you are drilling.

[epipete]

John, thanks.

As the pic shows it is the bottom bolt (the top one has been loosely reinserted) and most of it is sitting proud by about 3/4ths inch.

image.jpg

It was worth removing it as I can see that the thermostat was shot and given the state of the sensor that also looks in need of renewal (wish I'd removed it first). As you can see there is a level of muck, crud & oil commensurate with 20 years of neglect (not saying vital works have been ignored but certainly general cleaning has).

[Brit-Car-Nut]

I think that is good news. I would clean it up completely getting rid of all of the corrosion and film. Be careful to clean the recess without rounding the square edge too much.

I would put penetrating oil on the stud at the housing and carefully get a heat source to the thread area from the thermostat hole. You want to slowly heat the area to get it to expand a little. Add more pennetrant as necessary. Pack the area around it with rags or towels to keep things as clean / neat as possible.

With the "good" bolt removed, you can probably get a good grip on the remaining shaft with a pair of mole clamps. Clamp them as tight as you can. Push on the mole clamps to rotate the bolt but not push the bolt itself downward. If it moves, spray more pennetrant and re-tighten before repeating taking bigger arcs each time until the remainder is out.

A stud remover like http://www.ebay.co.uk/itm/Assenmacher-A ... 0701703109 is a nice tool to have while one like http://www.ebay.co.uk/itm/Stud-Remover- ... 0291939027 will work, but you need to make sure it doesn't try to bend the remainder of the bolt and crack the ear. I usually set one like that up with the ratchet crossing the tool (and stud) rather than extending beyond the fitting outward. The latter gives a lot more torque but also bends the remainder as you push.

[Brit-Car-Nut]

When you have sorted the bolt issue, to avoid the very common problem of the thermostat falling out of the recess as you reassemble, use a bit of gasket glue on the edge of the thermostat at the top (12:00) point to hold it in place as you fiddle with the other things around it. I don't like silicone for areas like that, but that is my personal preference. Silicone will actually lubricate and as you tighten, the gasket canslide as it is tightened and might stretch or tear. I use Permatex 99ma Spray Tack or brushable "aviation" gasket sealer and I let them dry before assembly.

Remember, if the thermostat has a wiggle pin or bleed hole, they always goe at the highest point so the thermostat chamber remains full.

[Jeemy]

The best advice I got when trying to release these kinds of things, was to start a week early. I can't emphasise enough how much of a difference a bolt soaked in PlusGas for a week is to release, than one soaked for an hour.

Drip it in, and repeat for 7 days. Bear in mind this stuff is flammable, but also apply heat with a butane/propane torch and let it cool, repeat. Just to let the things expand and contract a couple times.

The second really useful thing was to make the first impact it to TIGHTEN the bolt rather than loosen it. I often put a solid wrench or spanner on and tapped it (hard) with a hammer. After that, sometimes they came out. Sometimes they snapped. Sometimes I had to drill them out. But sometimes they just worked perfectly after PlusGas, heat/cool/heat/cool, tap to tighten, then loosen.

[racerstev]

I find heating the head of the bolt until it just starts to turn red and no more does the trick.
The steel is expanding at that temp but the aluminum will expand much more and release the
bolt. Be ready to carefully work the bolt back and forth to help clean the gunk off it.

Also wake the bolt up before you start heating it, give it a few hard hits with a punch from the
side of the bolt to loosen things up.

Steve

[HJ2]

Once again excellent reading stuff guys!

[epipete]

I almost feel that I should be posting under 'things that made you smile today'!

A bit of judicious heat, plenty of penetrating oil and, whoa, out it twisted, cleanly on a pair of mole grips, today life is good! Tomorrow, gear cables, maybe not so!!!

Thanks for all the advice.

Pete

[epipete]

Just a thought, & again my ignorance is clear to see but, in respect of replacing damaged/broken bolts etc is there a standard to which these should be replaced? I realise that non critical fixings such as on heat shield brackets etc are not particularly important but in respect of other items such as the thermostat cover does it really matter?

Can I source these (and others) at B&Q or is there a recommended supplier? I'm kinda concerned about putting my spanner anywhere now and need to release the bolts on the gear change bracket next!

Pete

[dapinky]

Pete,

As you say - rule-of-thumb is that non-critical fasteners can be any grade (but you site the heat shield ones - whilst they are not load-bearing, I believe they may be made out of something other than steel, for heat conduction - that said, I used stainless steel ones to fit mine - coefficient of expansion of stainless is so similar to that of Cast Iron that it made no difference).

Basically, if you look at the head of the bolt it will be marked in some way to show it's 'grade' of steel.

The usual (EU anyway - those Colonials like to be different!) thing to see would be 8.8, 9.8,10.9 or 12.9....

There are other grades (higher and lower), but not that you need to worry about.

If there is no marking, then it's just a mild steel bolt with no torque 'standards'.

8.8 is what is usually referred to as 'High Tensile' - the first '8' is the torque that it will hold (800Nm), and the second '8' means that once the bolt gets to 80% of it's breaking strain, it will start to permanently deform (stretch).

Likewise, a 10.9 bolt will go to 1000Nm, and won't deform until it gets to 900Nm - easy to decipher once you know the nomenclature.

If you use Stainless, they have different markings - the first letter and number denote the material class A2, A4 etc, then the second is the torque strain rating.

ie, A2-70 is okay for most conditions, but A4-80 is good for corrosive (marine) applications, and has a higher torque rating - the -70 or -80 equates to 700Nm & 800Nm respectively - so an A4-80 is as 'strong' as an 8.8 High Tensile steel bolt (well, not quite that simple as there are other forces to consider than just Tensile strength - but as near as makes no difference to us!)

Just as a comparison, a non-marked steel bolt will have a tensile strength of around 3.5, unless it's made in the Peoples Republic of Hartcliffe, in which case you're better off with chewing gum!


PS - if you look in the parts book it will tell you the necessary strengths to use - but only if it needs more than the 8.8 'standard'

Unfortunately, my main Laptop has got a knackered keyboard, so I'm using my old one, and don't have the parts manual on here so can't look it up for you, but i would think about replacing the bolt with a stainless one, but whatever you use make sure that you use copper grease on the bolt where it passes through the unthreaded aluminium - Steel and Aluminium are at opposite ends of the Nobility Scale and therefore suffer badly from Galvanic Corrosion (those loose bloody electrons get everywhere!) - Copper is somewhere in the middle so it stops the reaction - of course, being a rich ex-Civil Servant, you can probably afford to get them gold plated, which is even better

As a guess, I'd assume the bolt is something like an M8x60mm - and all 'standard' sizes are availlable quite cheaply in small quantities on ebay - or failing that, I've got a couple of meters of threaded A4 Stainless bar and a fair few nuts, so knocking something up isn't a problem once i know what length to cut it to

[epipete]

Thanks, Dave, for enlightening me, between you and John I am learning more and more. I fear that I have wasted the last 50 years, I know nothing at all about this subject and hitherto thought a bolt was a bit of threaded metal with a nut on 'other end.

Pete

[Fredjohn]

And I thought a bolt was what a horse did, with a nut on

Pete: there may be a local fasteners wholesaler near you (Bath? Swindon?) who can supply you with whatever you need. In Coventry we have Kebrells, who are brilliant and also nearby Leamington Spa Fasteners. So very easy for me to get virtually anything in that line.

Dave now I too understand:

[lotusnut]

I find that it is usually better to attempt to loosen bolts such as these after you have got the engine to operating temperature, once released, allow the engine to cool down sufficiently to drain coolant, then soak bolts in plus gas, leave for a while and then remove the bolts.