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Hyundai Accent G4EA head sealing
#1
Just done a head gasket change on a UK spec '05 Hyundai Accent LC with the 1.3 SOHC 12 valve G4EA engine. The gasket is 3 layer metal with swages around the larger holes and coated with a black sealant material. Having reassembled the head I'm unhappy with the way some of the head bolts felt on reassembly. I'd be grateful for some expert thoughts.

The head was cleaned and inspected and found to be in good condition and within specification for surface finish / flatness. All surfaces, bolts, washers, threads and lands were cleaned and I threaded each bolt down its hole by hand to check for excessive friction or damaged threads; all were OK. Bolt threads were lightly oiled with engine oil (10W30) but I didn't think to oil the washer faces. Tightening sequence is torque to 18 lb ft - loosen 90 degrees - tighten to 18 lb ft - tighten 60 degrees - tighten 60 degrees. which I followed, measuring not guessing the angles.

I tried to establish whether the head bolts were single use (TTY) and could find nothing either on owners' forums, parts suppliers' sites or in the manufacturer's engine manual to suggest the bolts should be discarded. Bolts appeared to be in good order with no waisting, necking  or thread damage.

On loosening the bolts after the first tightening I found the centre two bolts (first to be tightened) had come slightly loose once the others were tight. On the final 60 degree tightening, the last two bolts - 9 and 10 at the outside front corners - seemed to tighten well initially, but didn't tighten progressively; there was a point from around 40 to 50 degrees where much less torque was needed to pull them round, though they did tighten again in the last few degrees of the pull. Checking the centre two bolts again gently, they felt as though they might be loose again, though I didn't pull them further.

Gut feel is that the bolts have not tightened evenly; however, this is gut feel and may be meaningless. I don't want to finish assembly to find the gasket blows again in a short while; however, I'm reluctant to do the job again, possibly to have a repeat of the same. I'm concerned that the bolts should have been replaced or that something else is causing problems, such as uneven tightening caused by dry bolt heads and washers. I'm in two minds whether to leave it alone or loosen, lubricate and retorque the bolts, either one at a time or all together, or whether I'm worrying unnecessarily. Any thoughts appreciated.
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#2
Hi Sean,

I talked to John Gurnig from the Fel-Pro Field Test Garage about this one, here's what he said:

"Based on what I could find, the 1.3L is similar to the 1.5L engine released here in the U.S. The torque specs are the same and I found that Hyundai states there should be no problem reusing the head bolts. That being said, depending on the reason for your head gasket replacement, a severe engine overheat, may warrant replacing the head bolts.

The fact that you did not oil the head bolt washers has little effect on the torque-to-angle. It has more effect on the torque wrench and when it will “click off”. Torque wrenches work off of friction.

TTY fasteners take out all the things that can affect a torque wrench reading – bad threads, lack of lubrication, type of lubrication, torque wrench calibration & so on, but these bolts are TTA, not TTY.

Over the many installations of engine components I’ve done, I’ve found that cylinder heads, intakes, valve covers and more will need to have the center bolts re-torqued after completing the torque sequence. Everything settles in and the center bolts will move again when using a torque wrench. This does not apply with the final portion of the torque sequence with TTY bolts - those shouldn't be torqued after completing the sequence.

Your head bolts may be weakened from mileage or engine overheat and thus may not “feel right” during the torque up.

I understand your worries & frustration. I would recommend purchasing a new set of head bolts and removing them one at a time in the torque sequence starting at #1 bolt. Lube the threads & head bolt washer areas. If the old head bolt comes out with metal shavings on the threads, then we know the block threads are giving up, the head will have to come off & the block threads repaired. If the head bolt comes out clean, starting at the #1 head bolt, torque it to the 18 ft. lbs., then the 60 degrees and the final 60 degrees. Repeat this process at each head bolt in the sequence. This process will prevent you from having to purchase another head gasket.

You may have to pull out one head bolt before you start this process to get the correct bolt set for your engine, unless you have a source of a set that is confirmed to fit the 1.3L engine. The set for the 1.5L engine (ES 71201) are slightly longer than head bolts the 1.6L engine (ES 72203). Remove one head bolt and consult FME-Cat.com, searching each part number, then looking under "specifications" to see which is the correct length head bolt for your application.
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#3
Gents, thanks for your input, it's very helpful. Hopefully these follow-up comments will help anyone coming along after.

I believe you're correct about the similarities between the 1.3 and 1.5, being the 'Alpha' engine. That you have found Hyundai confirmation the bolts are re-usable is good to know; I was only inferring, having not found anything to say otherwise.

Your comment about the centre bolts is interesting too. I'm mainly used to classic vehicles with iron heads where there is a set torque figure for each stage. In those circumstances I would have re-checked the bolt torques once the sequence was complete, often finding as you do that the centre bolts will take a re-torque. I don't regularly work on (TTA) engines that require the bolts to be pulled through angles, and I was at a loss as to how to re-torque accurately with no final torque! It seems the only way to do this would be to loosen one at a time then repeat the sequence as you suggest.

The head gasket replacement was due to a misfire and fault codes registered, triggered by a loss of compression on Nos. 1 & 2 cylinders. There was no report of overheat or signs of it and though there was a slight loss of water with traces of leakage on the block face, the blow was mainly cylinder to oil way. The vehicle has only done 56,000 miles, which is another reason I was initially comfortable re-using the bolts after inspecting them.

I will replace the bolts one at a time as you suggest provided I can source a new set, inspecting again as I go. I'll oil the washers as well this time just to ensure the initial torque is as accurate as I can get it. I'll follow up here in due course.
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#4
Good luck Sean, and you're welcome - let us know if you have any other sealing questions!
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#5
Went back to this job yesterday.

I struggled to find anyone in the UK who was able to supply the head bolts (reasonably quickly, anyway), so I ended up withdrawing the old head bolts, inspecting each one, cleaning and re-oiling bolt and washer and replacing it to the specified torque / angle, doing them one at a time as suggested while leaving the others torqued down.

There was no sign of thread damage, waisting, significant length or diameter variation or other problems with the bolts, no metal debris or sign of any damage to the block threads, and all the bolts threaded cleanly into their respective holes by hand, so I was reasonably comfortable re-using them.

The good news is that the bolts all pulled down evenly and progressively without signs of slip, and on check pulling the centre bolts (just applying a load, being careful not to pull them further) there was no sign they had loosened; so it looks as though the procedure was successful.

Thanks again for the help and information, and can you pass on my sincerest thanks to John Gurnig.
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#6
Sean,

John and the rest of us are happy to help and are glad to hear that the bolts torqued up properly!
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