Head bolts won't come loose 4

[tcp2000]

Steel head bolts holding an alumium head onto an aluminum block won't come loose. On the first round of breaking torque, I was able to only get a very small turn on each 10mm bolt (I was also being very carefull).

On the second round of loosining, the first bolt I tried broke off inside the block (sucks!). The rest of the bolts look as though they also want to break. The heads of the bolts "flex" slightly when loosining torque is applied and then they return to their orginal position when torque is removed. This is the way the first bolt behaved before breaking. The bolts seem to be seizing in the block where the threads are and not at the heads of the bolts.

I have already removed the left head from the block and I did not experience these kinds of problems.

I was wondering if anyone has a "trick" they can share to get these bolts out without breaking anymore of them...

 

[phasers]

I've always wanted to get my hands on the guy who came up with the idea of putting steel bolts directly into aluminum. The bolt has annealed and fused itself to the aluminum threads. It's a good fusing too as you mentioned the bolts are flexing from the wrench torque. Japanese engines were notorious for this. I've repaired many aluminum intake manifolds where the carb bolts broke at the base and had to be removed and repaired. You can try some penetrant such as WD40 you might have a chance, but if it's a good fusing then you're out of luck. If you do go the WD40 route, wait. Be patient. WD40 is a penetrant not a lubricant. It is really fascinating stuff. It works on a molecule to molecule progression so it takes a while to work. Sometimes over night and don't be stingy with it, saturate the area often and let it set.

The other choice is heat. If you could cut or otherwise remove the top of the head bolt (the blue wrench may be needed) to get the cylinder head out of the way, use a torch to heat the bolt red hot. Let it cool a bit and give it a try. You may have to do it a few times to break it loose. You may also want to tap on the bolt as it gets hot to vibrate the shank and this sometimes loosens the grip. It's a touchy prospect. If you do try it, turning the bolt while it's still red will probably destroy the threads in the block. The aluminum block being thicker than the bolt dissipates the heat away. I used to remove broken studs from heads this way but you have to be careful. Chances are you are going to destroy the threads but I can tell you it's easier to repair the hole where the bolt was, then trying to drill through the annealed steel still stuck in the hole.


good luck.


Phasers

 

[wroberts]

The reason that things like this get designed is that most engineers have never worked on anything old, or took wood or metal shop in high school. When I was in school, I was the only one of the mechanical engineers that took shop in high school, and had actually worked on anything that wasn't brand new. At a former job I got into several arguments with my PHD Mechanical Engineering boss that putting steel bolts into an aluminum housing for a differential was wrong. The non-engineer prototype/shop guy agreed with me, and after testing the differentials the only way to get the thing apart was to cut the bolts off and throw away the housing. He still didn't beleive us and it went into production over my persistant complaining.
The basis for his opinion was that they had always done it, and were able to build and take them apart before.
However the parts that what he had always worked on were new parts, not older ones that had annealed and fused itself to the threads. This process takes time something that he never saw, and therfore made poor decisions from his lack of practical experience.

Will

 

[ivymike]

Out of curiousity, what was the alternative fastening method that you were suggesting? Threaded inserts?

 

[wroberts]

The way I wanted to fasten them in was with bolts, instead of a boss on the housing with threads. This was the way they were originally designed. The boss was a cost save that saved $0.04. While it cost almost nothing for the boss the housing then had to have the threads machined in. The volume on this part was low. I just thought it was very short sighted to produce a part that in our service manuals is a servicable part, but is impossible to service.
My point being is that I would like to see more engineers take a closer look at designs that have endured time and use.
The parts we design today may have done the designed life span. Say 500 hours of use till maintenance is needed. This testing will be done in 21 days. However a homeowner may only use the device for 20 minutes a day. By the time he/or she is up with with that life span it will be 4.1 years. The difficulties the user faces servicing the piece of equipment will be quite different than the engineer tearing apart a 21 day old machine. Problems like steel fasteners fused to aluminum will be very apparent to the user but not the engineer.

Will

 

[hoyle]

Hello

There are senior engineers (like me) out there who work on 30 year old cars, and are used to pulling rusted bolts out of difficult places.
The reason why steel bolts are used, is simple, for the cost, steel is a great material for fasteners. The reason why aluminium is used for engine blocks and especially cylinder heads, is because of weight, heat transfer, etc.. etc..

For a start the bolt hasn’t annealed, it has corroded with the aluminium through galvanic action. The aluminium thread has “sacrificed itself” and plated the bolt. This all happens at a very small scale. But it is enough over a period of time to seize the bolt permanently. And if it has seized do what the man says above, soak them in WD-40 for at LEAST 24 hours, and I mean SOAK.
Then try and undo the bolts gently, and get a feel for how much torque is required at the wrench to make the bolt heads JUST move. Then gently rock the wrench back and forth using the same torque in both directions. What this does is loosen the seizure at the top of the thread where the most strain is taking place. Once this happens, you will feel the torque reduce by a slight margin, spray some more WD-40 on, leave it to soak in and do the other bolts. Return to the first bolt and keep doing this for as long as you think it’s working. It works in about a half of cases. Most people think if the bolt doesn’t move on first torque application, they just use more brute force, and then snap the bolt.

If that doesn’t work, remove the top of the bolts with the some VERY careful grinding and/or chiselling and/or machining.
Take the cylinder head off
You now have access to the bolt shank, but not of course the bolt head.
If, and I mean if, you are lucky the bolt should turn with a light torque, if not the bolt is seized. Then heat up the bolt with a torch, Grab the bolt shank tightly with a wrench and rock the bolt shank back and forth gently, don’t let it slip though! Then let it cool down; cool enough so you could touch it.

Tip, place a small dab of nail varnish/cheap paint on the bolt where it enters the block, this usually changes colour before any harm comes to the block, best to check paint suitability before ruining an engine block!

Repeat this process, it may require the heating and rocking process 3 or 4 times. It doesn’t take that long in real life, honestly, I too have rebuilt motor cycle engines.
If this doesn’t work, drill the bolt out, and have the thread recoiled. It doesn’t cost a machine shop that much, I have just had my Golf/Rabbit cylinder head done, it cost 6 pounds/9 dollars a hole.

What is interesting is how one cylinder head came off without any problem, and the other side didn’t. No doubt two different assembly workers, one doing all the left hand heads and the other doing all the right hand heads, and forgetting to use some lubricant. The most common reason for this type of problem, I have experienced, is someone buying slightly cheaper bolts for the line, and the plating/oiling has been dropped to get the price down.

The question now is what are you going to do on reassembly?
Change the design?
Use aluminium bolts? (I don't think so)
Put new steel ones in and hope for the best?

You do the last one, but the most important thing is to smear anti seize compound on the threads before assembly. It's grease with extremely small granules of copper in it. No steel bolt will seize in an aluminium block with this on it, well none of mine have! Don’t use a light oil or WD-40 again for this, it’s too thin. It works, but you might as well do the job properly.

But the problem still exists of senior engineers never leaving their desk and actually handling/making the pieces they are responsible for. I worked in one company where the design engineers weren’t allowed to operate any factory machinery, or make any parts of any sort for any reason. In fact it was instant dismissal. Oh the joys of liability insurance!
The worrying thing about one of the stories above is a PhD engineer being trusted with the product and an attitude of “we have always done it that way”, If I had a pound/dollar for every time I’ve heard that.

Hoyle

 

[wroberts]

Glad to hear of someone else thats into old stuff and good experience. I've never heard of the nail polish trick be fore I'll have to keep that in mind. I understand that there are many cases where your stuck with a steel bolt into an aluminum housing, but as you said a penny or 2 of anti-seize will save me (your customer, dealership, ect...) hours if not days of work.
So is doing preventative design (anti-seize) economical?
Lets say 100,000 vehicles, 5% will be serviced at a dealership. Lets say it takes a mechanic at a dealership an hour to get around stuck head bolts. ($50/hour) that leaves $2.50 a car to get anti-seize added to the head bolts.

 

[EMc]

Hello again.

Hmm... So, what you're saying is that between labor and materials at the factory, the manufacturer would be taking a loss by adding anti-seize to the head bolts?

Don't forget, also, that the manufacturer (and the dealer) do better at the bottom of the repair bill if you HAVE to get a new head installed because the bolts seized. Or a new engine. Or a new car....

EMc

 

[wroberts]

Well I think they are. The trend these days seems to be 100K powetrain warrenties, (Crysler, Kia, ect...) Engine problems, valve train, head gaskets, ect.. should be covered by the powertrain warrenty. You the consumer don't pay for it the manufacturer does.
Obviously this assumes there is something servicable on the engine. I beleive that Ford has a motor that if you need to replace the timing chain it's cheaper to buy a new engine. I wouldn't want that, would you? Maybe I'm weird but I enjoy being able to work on my vehicles, not that I always want to be fixing them but should I need to I want to be able. When I look at new cars one of the first things I look at is servicabilty of the engine and drivetrain. How easy/hard is it get at the plugs, alternator, brakes, exhaust, change a belt, the oil. If a car is lacking these things I will not buy it. I plan on keeping my vehicles for the long term and buy and maintain them accordingly. I detest, hate, loathe, dealerships. If I blow a fuse on the road I'll die in a desert before I'll call the 24 hour roadside assistance to have it towed to a dealership to get a fuse changed. Leasing a car is a total waste of money.
While I'm sure I don't fit the average consumer, this is the reason I'm a ME and working in the auto field for 1 of the big 3.

 

I would like to ask Hoyle (and anyone else)about the torque to yield bolts on current engines,why are they used and what engineering principles are involved. Is it absolutely necessary to use new ones or is that more of a marketing racket? I know that every manufacturer says to replace them, but from a practical point has the bolt really yielded enough to weaken it on a second use, or reduce ductility to the point that it will fail in brittle fracture?
Thanks

 

[evelrod]

YES, replace torque-to-yield fasteners EVERY time!!!

As a matter of fact, I replace ALL stressed fasteners in my engines at each teardown/rebuild. It is just NOT good economic practice to risk a high dollar engine for a couple of hundred dollars worth of bolts!!!!!! I have used low time parts, rings, bearings, etc. on occasion,(as per Smoky's reccommandations) with success, but never put the same bolts back after they have been used.
SPS and ARP make very good stuff at very reasonable prices, money in a rebuild should not be a good excuse for not using them. Cosworth and a couple of other mfgrs DO have some REALLY high dollar bolts, but I, for one, question whether they are any better than ARP. I used Cosworth rods for many years and replaced the factory bolts with SPS and had no failures in 28 years. If memory serves me the SPS were about 10 times cheaper than the Cosworth.



Rod

 

[evelrod]

AND --- to the original post, once the aluminum block material has bonded to the steel bolt threads, they will NOT break loose. All that will happen, even with heat cycling and 'penetrating oil'(an oxymoron, if I ever heard one), is the bolt will break or the block threads will come out with the bolts. K&D or HeliCoil inserts , or similar , will be required to repair (if you lucky enough to get the broken pieces out).

I've said this before, but to get everybody's knickers in a knot, I'll say it again---"I apologize to all you folk who are convinced that 'penetrating oil' will work, I have tried them all in the last 50 odd years. They still don't work."


Rod