Rebuilding Motor!

[Sik95TSI]

So today I got the news that I need a rebuild Shop called me and said they did a compression test and got 120-125 across on all four, also they did a leak down test and it failed that too WTF This is funny because I only have about 150 Miles on this new set up!!! My last mechanic who did all the work told me everything checked out and looked good before doing all mods "Head checked out at machine shop too" Anyways I have a few question's. I'm sticking with my 7 Bolt anyone have any suggestions on what to get I was looking at the MANLEY 4G63/4G64 ROTATING ASSEMBLIES anyone ever use this set up? Money is not a problem. I will most likely pull the motor myself and send it out to shop to be built I will also provide all parts needed. Second is there anything in specific that can cause low compression besides rings,valves,seals??? Any info would be great thanks guys!

 

[Sik95TSI]

Ok so I decided to start my car today to put in garage since I got it back from the shop (it was towed there and back) When I went to fire it up it was misfiring bad!!! I let it warm up to see if maybe it would get better and it didn't. So I decide to call shop that worked on it and the guy said all they did was leak down test and compression test all they touched was the plugs and wires. So I started to check things out myself and decided to take the plugs out. Spark plug on cylinder one was smashed no gap what so ever I checked the rest and they where fine so I got all new plugs and it runs fine (well like it used to before bad plug) if this shop put my car back together like this I'm wondering if they even did the compression/leak test right when I talked to the guy he mentioned we didn't start the car at all :wtf: I thought compression test was suppose to be done at operation tempsture right? I have my chilton book and I'm seriously checking timing tomorrow.

 

[WES_393]

I thought compression test was suppose to be done at operation tempsture right?

Yes, it is. Warmed up and throttle plate all the way open. Seems to me you should start checking things over and then report your findings to the shop.

Also, what was the results of the leakdown test? Something like "Good" is never an acceptable answer. They should be able to give you a % of leakage per minute and the suspected areas of pressure loss.

 

[Sik95TSI]

Yes, it is. Warmed up and throttle plate all the way open. Seems to me you should start checking things over and then report your findings to the shop.

Also, what was the results of the leakdown test? Something like "Good" is never an acceptable answer. They should be able to give you a % of leakage per minute and the suspected areas of pressure loss.

I did in my earlier post you can read what numbers I posted. One thing though he said you want to disconnect ecu when doing compression test because injectors will spray fuel while cranking "obviously" and that causes to get inaccurate readings or give you higher numbers WTF I've never heard of this.

 

[WES_393]

I did in my earlier post you can read what numbers I posted. One thing though he said you want to disconnect ecu when doing compression test because injectors will spray fuel while cranking "obviously" and that causes to get inaccurate readings or give you higher numbers WTF I've never heard of this.

My apology, I must have missed that part. Unplugging the ECU might be a bit extreme. Most people either unplug the MPI relay or just unplug the injectors from the harness. But yes, fuel being injected can give a higher reading.

 

[Sik95TSI]

My apology, I must have missed that part. Unplugging the ECU might be a bit extreme. Most people either unplug the MPI relay or just unplug the injectors from the harness. But yes, fuel being injected can give a higher reading.

So then exactly what is the correct way to perform a compression test on a 4G63?

 

[WES_393]

Warmed up, throttle plate completely open, injectors (or relay) unplugged, all spark plug removed, and 4-5 cranks of the engine. At least that's how I've always done it.

 

[Sik95TSI]

Warmed up, throttle plate completely open, injectors (or relay) unplugged, all spark plug removed, and 4-5 cranks of the engine. At least that's how I've always done it.

All spark plugs out together at once???

 

[WES_393]

All spark plugs out together at once???

Yes, it makes it so there is no compression on the cylinders not being tested and the starter is free to use 100% of it's power on just one cylinder. When you start a car and hear the gaps in the sound, that's the starter fighting the compression of the engine. You're only getting the reading of one cylinder at a time so you want that cylinder to be free to spin at full cranking speed, not getting slowed by the other cylinders compressing.

I hope that all makes sense. It might sound silly, but you want to rule out as many variables as possible. 15psi could be the difference between an engine being "good" and "needing a rebuild".

 

[Sik95TSI]

Yes, it makes it so there is no compression on the cylinders not being tested and the starter is free to use 100% of it's power on just one cylinder. When you start a car and hear the gaps in the sound, that's the starter fighting the compression of the engine. You're only getting the reading of one cylinder at a time so you want that cylinder to be free to spin at full cranking speed, not getting slowed by the other cylinders compressing.

I hope that all makes sense. It might sound silly, but you want to rule out as many variables as possible. 15psi could be the difference between an engine being "good" and "needing a rebuild".

No I understand I just wanted to make sure oh trust me I know I really need to get to the bottom of this

 

[fierosail]

1 Let the car run for about 5 minutes, you always want to compression test a warm engine for best results.
2 Disable the ignition system so the engine does not fire up during testing.
3 Label the spark plug wire or just know where they go
4 Insert the compression tester into the cylinder spark plug hole and tighten by hand only
5 Have your helper crank the car’s engine 7 to 10 times continuously to obtain the most accurate reading on the compression gauge.
6 Record the reading for the cylinder
7 Make sure that the pressure gauge returns to zero
8 repeat 4-7

The compression test is not so much about the absolute level of compression; it is the difference in the compression between each of the cylinders. If all cylinder readings are within 10 percent of each other, your engine compression is considered optimal. However, if any of the cylinders compression vary 10% or more from each other, a problem may exist

 

[Sik95TSI]

I'm getting ready to pull the head off right now as we speak and send it out to get double checked. Can you use the head studs again? I have ARP's. I'm going to have to get new head gasket as well.

 

[NHerron]

Yep new head gasket for sure

7BOLT/2G engine:
You can reuse the ARP's almost indefinitely, just don't ever over torque them. You must use ARP MOLY LUBE when reassembling and use a final torque of 75-80ft lbs.

Torque them in 3 steps in the correct sequence.
Follow this torque sequence
http://www.dsmtuners.com/forums/cyl...k/414809-head-studs-torque.html#post152733337

First torque them all down to 20ft lbs. Then 50ft lbs. Then 80ft lbs.
http://www.dsmtuners.com/forums/bolt-tech/381426-fastener-tech-101-a.html#post152322941

 

[Sik95TSI]

So I just got done I've been working on my car all day!! Come to know the timing belt was off, intake Cam was off by 1 tooth tensioner pulley wasn't tight at all and there was slack! I retimed everything and adjusted everything properly car starts better and idles way smoother!! I guess if you want something done right you have to do it yourself!!! Timing belt wasn't bad at all I'm very confident to go in there again myself!!

2nd I did a compression test and I got 150 across the board which is way better then what the stupid shop I took to said!!! I'll probably do another test in a few days just to confirm been a long day and I'm beat!

 

[NHerron]

Glad to hear it was easy enough to do while in the car Nice job on getting it done yourself

 

[alex209]

Nice job cars back to life

 

[dsmxfan]

good job finding the problem.

 

[fierosail]

doing it yourself dose to thing for me 1 you know it done right 2 you have allot of pride and joy seeing it done and it was you that did it and nice job glad it back to life

 

[Sik95TSI]

Thanks guys!! It does feel great to know that I did the work myself and that I feel confident in what I did! Also I'm very happy I decided to do this because it gave me more details on how the timing system works and how it should look and be done

Do you guys recommend doing a leak down test again? I'm still concerned if I have a Blown head gasket Because car over heated a couple times nothing major just little over half. I know it was a little low on coolant and timing was off and I've heard if timing off that can cause over heating issues ect...? Thanks

 

[gs59_20]

I did in my earlier post you can read what numbers I posted. One thing though he said you want to disconnect ecu when doing compression test because injectors will spray fuel while cranking "obviously" and that causes to get inaccurate readings or give you higher numbers WTF I've never heard of this.

This is a shop that doesn't know you don't need to unplug the ecu to perform a compression test. This is automotive basics. I could never trust a shop like this. The fact that I'm a noob to engines makes it look a lot worse on them.

Great job getting into your engine on your own finally though. It's the only way to learn and it'll give you a lot more piece of mind

 

[boost97gst]

I disconnect the CPS which disables spark and fuel. Then, have someone crank it over until i see the guage bounce up to the highest number it will hit. Thats your compression. This is done on a warm engine too. Atleast thats the way i was taught. Oh, and i pull all 4 plugs, just to make cranking resistance low as possible. Another little trick