New head gasket leaking – after replacement!

[Robert Grech]

Hello! Newbie here..

I’ve been eyeing the forum for similar problems, but their solutions don’t apply.

I bought a 1999 Yamaha R1 (yes, it’s a bike, but it’s a 4 pot internal combustion engine so… 😛 ) and it was mixing oil with coolant. Oil came out clean, but the coolant was a mess. I’m no mechanic, but I fix my cars myself.. timing belt here, regular services there, and so on..

I’ve basically rebuilt the engine, replacing every gasket in the way. (I bought a complete gasket set). I checked the cylinder head for warpage using a straight edge, found it to be straight as a razorblade. Anyway, put the new head gasket in, torqued it to spec (50Nm) and went forward with the rest.

I’ve reassembled almost the whole engine, except for the oil pan which had a tiny crack. It’s currently being repaired, so I went ahead to fill up the bike with coolant, just to make sure that it’s holding the water well.

This is where the sh!t hit the fan 🙁 . Just by manually pressing on the radiator hose, I saw tiny amounts of coolant forming on the exterior of the head gasket . A few hours later, this became more evident.. Just out of curiosity, I hand cranked a few turns, and I saw a fine spray of coolant going out of the exhaust ports. (Exhaust manifold is detached at the moment). Moments later I saw droplets of coolant dripping through the crankcase.

I’m at loss for words here – not sure where to start from – I mean I’ve torqued to spec and it’s as if I’ve torqued the head bolts with my fingers!..
My greatest fear is finding the head bolts torqued to spec and not being able to do anything more. I’m thinking about giving Steel Seal a try at this point.

Any ideas? Keep in mind that the motor hasn’t been started since the head gasket change.
I thank you beforehand for your advice!

Rob

Topic

[college man]

couple possibilities. Warpage on the parts or sealing surface not true flat. Head gasket
bolt torque not tight enough.

[Jim Davis]

If I am reading your post right, you have torqued the bolts, but they are now loose. Wait on the steel seal. Try retorquing the bolts, but only go about a third, see if it holds, then go another third of the torque value. Are they holding? If not, chances are you have either stripped threads, cracks in the thread bosses, or bad bolts. Hope for bad bolts or stripped threads, new bolts or heli coils or a similiar product can get you going.

[David]

Having worked in a parts store, its ALWAYS recommended to replace the head bolts anytime you take the head off, if you didnt? start there. From the sounds of it it sounds like you’re bolts arn’t torqued correctly

[Robert Grech]

Thanks for your replies!

One thing I didn’t mention is that the ‘bolts’ are actually studs that go through the head and into the engine block. Then the head nuts tighten the head to the block.
Their threads seemed healthy at the time, but I guess I’d better double check now.
The manual did not specify that I should replace the bolts/nuts, but at this point, I think it’s worth the hassle

[Jim Davis]

One more thing on those studs, you could be seeing stretch of the studs. Look up bolt stretch. Some bolts, especially head bolts, rod bolts or studs have to be measured for stretch, and it could be your threads are ok, but the studs are stretching. Just another thing to consider.

[Robert Grech]

Here’s an update:

So I got back to the head bolts, and checked torque.

On most of the bolts, I had to torque up to 1/3 or even 1/2 turn till I got to the target torque of 50Nm.

At this point I’m waiting a few hours (heck, even days) to check torque again, hoping they are done stretching..

Let’s wait and see!

[Jim Davis]

One thing I should have mentioned, if the studs stretch that much they may still need replaced if the originals, I am not sure I would trust them. Some new bolts/studs are designed for single use, and stretch when torqued. You usually torque, then use a angle gauge to turn an additional so many degrees to a final setting. Just watch things carefully. New studs could be cheap insurance for a lot of hard work.

[Author]

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