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2003 XC70 - Low Compression after head rebuild Topic is solved

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chrism
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Re: 2003 XC70 - Low Compression after head rebuild

Post by chrism » Sun Mar 25, 2018 6:29 pm

Turning the crank one full revolution will do nothing besides turn the cams 1/2 revolution if the belt is still connected. If the belt is off and you turn the crank one turn, you have accomplished nothing.

A couple questions:

In the course of your work, did you unbolt the cam sprockets from the cams?

When you have all three timing marks on target, and you look at the cam slots on the back end, is the intake cam slot slightly ABOVE center and the exhaust cam slot slightly BELOW center?

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Re: 2003 XC70 - Low Compression after head rebuild  Topic is solved

Post by firstv70volvo » Sun Mar 25, 2018 8:42 pm

Based on the picture of the crankshaft timing belt pulley and the fact that's it's been running without the center nut I would mark the pulley in relation to the crankshaft, pull the pulley off, check the condition of the splines and using the mark check if the pulley is still oriented correctly on the crankshaft. When the splines are good the pulley can only go on the crank one way but if the splines are damaged all bets are off. It may be a pain to pull it off but this really does need to be checked in my opinion. If this is your problem and the pulley has slipped enough (due to damaged splines) to cause low compression and a no-start condition but not enough to damage the valves yet it might be a good thing the engine didn't/doesn't start and make the pulley jump/slip even more on the crank and then ruin all the work you've done so far. The details you've provided show the timing is correct but if the crankshaft timing pulley is mis-oriented on the crank you'll never be able to time the belt correctly.

wieselaj
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Re: 2003 XC70 - Low Compression after head rebuild

Post by wieselaj » Mon Mar 26, 2018 7:09 am

Well... i have only been able to pull the timing belt pulley about an 1/8 of an inch out so far so I haven't gotten a good look at the splines. Once the crud/rust broke free, i can clearly see some rotational wiggle. Not good. Probably rotates a half a tooth without the crank moving. I am going to pick-up or hopefully borrow a jaw puller from the auto parts store.

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Re: 2003 XC70 - Low Compression after head rebuild

Post by firstv70volvo » Mon Mar 26, 2018 9:08 am

A jaw puller should pull the pulley off relatively easily. If the splines are damaged hopefully it's like the pulley splines in the photos previously posted and only the pulley splines are damaged so you'll only have to replace the pulley hub. If you do find that the splines are damaged and the pulley has slipped on the crank or there's a lot movement you'll need to determine just how far off the crank timing is off and be very careful about any crankshaft movement. You'll see the double spline area that keys and orients the pulley to the crank correctly and where this and the timing mark should be. Because your compression is still consistent across all cylinders (even though low) I don't think you've damaged the new valves so hopefully the pulley just has a lot of play and not actually spun on the crank or very little. If the pulley has slipped on the crank then the crank timing mark on the pulley will not be oriented correctly relative to the cams timing marks. Even if the pulley has actually slipped on the crank I don't think it's off by much otherwise your valves would be bent again so maybe you'll be able to get a new pulley and only have to make a minor adjustment to the crank position to get it timed right. This may all be a long shot and the pulley is fine but certainly worth a check to prevent further possible damage.

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Re: 2003 XC70 - Low Compression after head rebuild

Post by wieselaj » Mon Mar 26, 2018 11:54 am

The pulley was very difficult to remove with the claw puller, so I knew that I wasn't going to be happy with what I found. The splines on the pulley are in really tough shape. It might be hard to see in my pics, but they were nearly rounded flat. The splines on the crank are in better condition but are certainly showing signs of wear and tear. Keep in mind though... Cylinder 1 was at nearly top dead center when my crank was lined up so it couldn't have been too far out of time.

Image

Image

Anyone have a spare crank pulley laying around???
Last edited by wieselaj on Tue Mar 27, 2018 7:21 am, edited 1 time in total.

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Re: 2003 XC70 - Low Compression after head rebuild

Post by wieselaj » Mon Mar 26, 2018 2:28 pm

Just to clear up a couple of questions posed earlier in the thread.... I did not take the vvt hubs or cam sprockets off of the cams. I do not believe that the mechanic did either. The back of the intake cam has the slot slightly above center, with the extra notch above center, and the writing below the center. The exhaust cam is slightly below center, with the extra notch below center, and the writing above the center.

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Re: 2003 XC70 - Low Compression after head rebuild

Post by firstv70volvo » Mon Mar 26, 2018 3:36 pm

For some reason I can't view your latest photos, could you please repost them.

A new genuine crankshaft pulley part is ~$70 and hopefully you now have the 30mm nut for the crank end too. This could very well get you going again.

https://www.partsgeek.com/catalog/2003/ ... _gear.html

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Re: 2003 XC70 - Low Compression after head rebuild

Post by wieselaj » Tue Mar 27, 2018 7:31 am

I tried to re-post the images of the splines in my comment above... hope that helps. Lighting on the shaft splines is not great so maybe I will try to get a better picture after i spend a little more time cleaning it up.

I found a new crankshaft gear on ebay for 40 bucks so I pulled the trigger on that last night. I was skeptical that a slight turn in the crank gear could cause a big drop in compression. But thanks to the comments by firstv70volvo in this thread, I searched the site for things like crankshaft gear compression, etc. There are a few cases that seem to be very similar to mine that I will post below. The last one has a great video embedded in the thread. My gear splines look just as bad as his, though i don't think that I have that much rotational play in mine. Let's hope that I have the same positive resolution.

viewtopic.php?f=9&t=61771

viewtopic.php?f=9&t=58219

viewtopic.php?f=9&t=81631&hilit=cranksh ... ompression

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Re: 2003 XC70 - Low Compression after head rebuild

Post by firstv70volvo » Tue Mar 27, 2018 10:14 am

I hope this works for you Adam and I think it will. You've done a lot of work to this point with the head work and valve replacement so you're almost there. You provided a very detailed description of what happened to the car and what you've done so far, which is very helpful for others trying to help. The missing crankshaft nut is what caught my attention and my neighbor that had a Mazda Miata that wouldn't start.

I've heard of this type of a problem more than a few times with older Mazda Miata's but the crank pulley in that car only has a single key to hold the pulley and the crank keyway would get pounded out of shape, the Volvo has splines all the way around so seems like a more robust design. With the nut missing though the pulley likely had some minute amount of play and during the stresses of running and over time the splines wore or were pounded out of shape until play developed. Please let us know how it works out when you receive the new pulley and install it.

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Re: 2003 XC70 - Low Compression after head rebuild

Post by wieselaj » Mon Apr 02, 2018 12:16 pm

Correction (to my preceding post), I did have as much play as the guy in the video after cleaning the splines on the gear and the shaft. However, the innermost quarter inch of the shaft is not splined, so the corresponding splines on the gear were in much better shape. When I pulled the gear out a bit, that first quarter inch of splines on the gear bites and the rotational play is greatly reduced. That proved to be a good sign for the condition of my shaft splines. When my new gear arrived on Thursday, it was nice and snug on the shaft. I will try to post a video....

[youtube][/youtube]

After mounting the gear and the crank pulley, I re-installed the timing belt and unbolted my cam locks. I rotated the engine twice to make sure that I was in time and I hooked up my compression gauge to cylinder 1. Turned the engine over and BOOYAH!!

Image

As a reminder, I was only seeing about 60-65 PSI dry, so this was a huge leap in compression. I didn't even wait to test the other cylinders, just installed the plugs and coils and figured I would try to start it up. After a bit of hesitation, it came to life with a cloud of smoke (cylinders and intake were likely still full of ether and seafoam) and a REALLY ROUGH "idle". I let it run for a bit and then shut it down. The computer threw misfire codes for all five cylinders. I think the seafoam probably had something to do with the codes but I could tell that at least one cylinder wasn't firing. I pulled the coils back out and the spring fell out of #5. I ordered a new coil from Amazon and it arrived on Saturday. Cleared the codes and fired it up and it ran much better, but still not great. Computer threw a misfire code on #2. I disconnected that coil while the engine was running and there was no change. So another bad coil. The replacement should be here tomorrow and I am optimistic that is going to help it run well.

My other concern is that I am getting some smoke from the back of the engine bay near the turbo. I probably spilled some stuff (oil, seafoam, cleaner, etc) so I am not very concerned yet. I did have a couple of small liquid spots on the floor so could be a slow leak. I didn't unhook my turbo from the manifold, but maybe I jostled a seal loose removing and reinstalling the head. I crawled underneath this morning and could see just a bit of oil residue on the bottom of the turbo. It's something that I will have to monitor.

Here's a video of it running on 4 cylinders with the engine bay smoke...

[youtube][/youtube]
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