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Discussion Starter · #1 ·
I posted many months back about my engine smoking after replacing the intake manifold gasket. it was burning a lot of oil. I tore it down, replaced all bearings (#4 connecting rod looked bad). I overbored .5mm to clean everything up and got oversized pistons and rings. At that time I didn't check the flatness of the block or head.

The rebuilt motor didn't burn oil, but was using coolant. I tore it back down finding the block and head needed resurfaced. I had new valve seals installed when it was apart because I could see some oil on the stems when I did a closer inspection. I double checked all my clearances, made sure the rings were properly gapped, and I reassembled the engine will all new gaskets and new head bolts. I really feel that I properly torque/tightened the head bolts

At Initial start up of the 2nd rebuild the engine had a wisp of blue smoke, but it stopped after a minute or two. (not unexpected in my opinion) As the engine came up to temp, it started to push white smoke. It is still using coolant. Smelling the exhaust has no whiff of oil. The engine seemed to be idling smooth until the white smoke appeared.

I can only think of two possible paths of water to get into the cylinders. Somehow still coming around the head gasket or a crack in the cylinder. Maybe I didn't get the head properly torqued? Is it worth trying to increase the torque? Is that possible without pulling the timing chain/cover/engine?

I don't the paperwork from the shop to review if it was checked for cracks. Its back at my house.
 

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Discussion Starter · #2 ·
Thinking farther, and that my issues seemed to have started after replacing the intake manifold gasket. Is it possible that I'm getting coolant in from the throttle body? Has anyone heard of that happening?
 

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You mentioned cracked cylinders; could also be a cracked head. If you properly torqued the head bolts (per the shop manual procedure) don't retorque or tighten further. Since the procedure is a torque + an angle, there is no final torque spec for checking the bolt tension. You just have to get it right the first time.

Dave
 

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Discussion Starter · #6 ·
Well, I looped the hoses to the IAC Valve. It didn't solve the problems. Getting everything lined up to retorque the head bolts. Any other suggestions?
 

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Discussion Starter · #7 ·
You mentioned cracked cylinders; could also be a cracked head. If you properly torqued the head bolts (per the shop manual procedure) don't retorque or tighten further. Since the procedure is a torque + an angle, there is no final torque spec for checking the bolt tension. You just have to get it right the first time.

Dave
I did torque it per the manual. I feel that I remember in the write up that the shop did a penetrant check on the head. Unfortunately the receipt is at home (an hour from where I'm working on it). So I'd like to think that a crack is ruled out?

At this point can I do further harm if I increase the torque? If its cracked, I can't really hurt it further? I can rule out torque being a problem? The one question mark I had with torquing is if for some reason that there was more friction in the screws than factory anticipated, maybe I didn't get things tight enough before the + angle?
 

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Discussion Starter · #8 ·
For the lack of anything else to try before pulling it all back out of the car; I pulled the cams and turned the head bolts about 1/8 a turn. It has significantly improved the amount of white smoke. After running it for about 5 minutes; It calmed down to almost unnoticeable. However, the smoke returns when the throttle is rev'ed. Dying again after a few minutes.

The amount of smoke coming out is about what you would see on a cold morning start up. (its about 65 deg here today). I'm tempted to try another 1/8 turn?
 

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I would echo what was said about the proper torque values for various reasons. My question is whether you are reusing stock head bolts or using new OEM/ARP head bolts?
 

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Discussion Starter · #10 ·
I would echo what was said about the proper torque values for various reasons. My question is whether you are reusing stock head bolts or using new OEM/ARP head bolts?

I don't disagree with either one of you. Faced with the prospect of potentially cracked "something" I gave it a shot today and it seems to work out.
 

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I was using brand new Toyota bolts
...so torque then angle

Do a quick compression test to see if any cylinders deviate. A slight leak probably won't show up in a compression test but white smoke and noticeable coolant loss should. It's so easy on the MR2 setup because everything is right there.

To also add to this, make sure it's actually coolant in the exhaust before you panic. White steam from the exhaust is normal during warmup depending on ambient humidity and temperature.

If it passes a compression test, pressurize the coolant system to 15psi or so to see if it's actually leaking. It should hold pressure pretty well if it's all tight. It might just be bleeding out air slowly as you drive more which could be perceived as using coolant.
 

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The block and head mating surfaces should both be checked before a rebuild. I don't know what your results will be by applying more torque to the head bolts, it is not something I would consider doing. If your torque wrench was out of spec before the final angle set maybe you will have something for a while. Personally I don't think this will give satisfactory long term results. Possibly having a problem far from home and more frustration. Be aware that as bolts tighten they stretch, if they stretch past yield it is a problem. I measured the head bolt length when I installed a new short block a few years back, some where at discard spec. I was not planning on reusing, just curious. If the threads in the block strip it is a bigger problem. For long term success I suggest you find the issue and fix it properly. Doing it wrong means doing again which is inconvenient to say the least. I don't like problems when I want to get home.
 

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Discussion Starter · #15 ·
...so torque then angle

Do a quick compression test to see if any cylinders deviate. A slight leak probably won't show up in a compression test but white smoke and noticeable coolant loss should. It's so easy on the MR2 setup because everything is right there.

To also add to this, make sure it's actually coolant in the exhaust before you panic. White steam from the exhaust is normal during warmup depending on ambient humidity and temperature.

If it passes a compression test, pressurize the coolant system to 15psi or so to see if it's actually leaking. It should hold pressure pretty well if it's all tight. It might just be bleeding out air slowly as you drive more which could be perceived as using coolant.
I had followed the factory service manual for torque, unless I misjudged 90 degrees? Saturday it was definitely a thick bank of smoke. I looped the throttle body lines, and ran it for 2-3 minutes. It didn't seem to help. Maybe I didn't run it long enough to see if that was the actual problem? It didn't get warm enough to turn on the fans. After that I pulled the cams and added 1/8 turn to all the head bolts. When I ran it after adding torque the smoke cleared to almost unable to be seen. (took about 5 minutes of running)

It was a chillier day yesterday about 60 deg, so a wisp of steam wouldn't be unexpected. It was so faint you had to stand so something dark was behind the tailpipe. It didn't smell sweet.

The cars in my sisters garage, so I won't be able to get back to work on it again until this weekend, but if it has the similar faint wisp after warm up I'm going to call it fixed. I'd left the throttle body line even after I increased the torque. If it returns after I reconnect it I guess I'll have my answer!
 

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Discussion Starter · #16 ·
The block and head mating surfaces should both be checked before a rebuild. I don't know what your results will be by applying more torque to the head bolts, it is not something I would consider doing. If your torque wrench was out of spec before the final angle set maybe you will have something for a while. Personally I don't think this will give satisfactory long term results. Possibly having a problem far from home and more frustration. Be aware that as bolts tighten they stretch, if they stretch past yield it is a problem. I measured the head bolt length when I installed a new short block a few years back, some where at discard spec. I was not planning on reusing, just curious. If the threads in the block strip it is a bigger problem. For long term success I suggest you find the issue and fix it properly. Doing it wrong means doing again which is inconvenient to say the least. I don't like problems when I want to get home.
I didn't check the block and head until after the first time I reassembled the engine. (big mistake) I bought a Starrett straight edge and both the block and head failed. Both were surfaced, the crank polished, the head got surfaced new guides/seals and tuned up seats.

Toyota bolts are actually supposed to be tightened to yield. The way I looked at it was that the problem was down to either improper torque, or a crack somewhere. If I broke/stripped a bolt I would have to tear it down. If it was a crack I'd need to tear it down. Not much to lose?
 

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For the lack of anything else to try before pulling it all back out of the car; I pulled the cams and turned the head bolts about 1/8 a turn. It has significantly improved the amount of white smoke. After running it for about 5 minutes; It calmed down to almost unnoticeable. However, the smoke returns when the throttle is rev'ed. Dying again after a few minutes.

The amount of smoke coming out is about what you would see on a cold morning start up. (its about 65 deg here today). I'm tempted to try another 1/8 turn?
You really should not have added an extra 1/8 turn! The tightening process is a very highly-engineered one. By going higher than spec in head bolt tension you risk the following: distorting the head, yielding the aluminum under the head bolts, yielding the head bolts (they are not torque to yield!) which lowers the fatigue strength of the bolts, worse head gasket sealing due to distortion of the gasket sealing surfaces, increased cylinder bore distortion (because cylinder bores are distorted by the head bolt loads). I know the above from direct experience in engine design. The OEM spec is the best sealing you can get with a healthy block and head.

Has the engine been significantly overheated?

Dave
 

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Discussion Starter · #18 ·
sign. The OEM spec is the best sealing you can get with a healthy block and head.

Has the engine been significantly overheated?
It was before the rebuild/resurfacing. Everything after surfacing meets the .05mm or less with a straight edge.
 

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The tightening process is a very highly-engineered one.
Tell that to uncle Joe throwing some new piston rings in the 1995 Camry with the motor still in the car and everything propped up on some tree stumps in the back yard. Not a torque wrench within a 10 mile radius. He'll get another 300k out of it though.

Also tell it to some of my local Audi dealership techs bashing R8 head studs in with the impact on setting 3. That is a proven method for sure.

I'm just trying to stir the pot of course.


Regardless, this thread is a prime example of the of the way most things unfold. There is some smoke out of the exhaust, must be a head gasket, tear it all apart. It's a good thing MR2 spyders and 2zzs are dirt cheap and easy to work on. If this was Porsche motor shoehorned above a subframe, I hope there would be a different approach.
 

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It was before the rebuild/resurfacing. Everything after surfacing meets the .05mm or less with a straight edge.
If an aluminum cylinder head is severely overheated, part of the head can be annealed (softened) and this can hurt its ability to seal.

Dave
 
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