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Discussion Starter · #1 ·
Is it possible to do a compression test with the turbo off? I bought a 2000 Jetta with 120K that had runaway hoping that the turbo may be the only issue. Previous and only owner was able to stop car within seconds with the key and then restarted and limped a mile home. Before I purchased a compression test by a local enthusiast gave 440, 390, 280 and 460 (1-4). The dealer replaced the turbo at 80K due to limp mode. After removing the turbo, the VNT failed the vacuum test described in forum FAQ. No apparent damage to turbo blades. Maybe a mm of play (across and along) turbo axis. Heavy build-up (10-15mm) found on intake and EGR. MAF sensor. A regional guru suggested that excess oil from the runaway could affect the compression test readings. I am trying to decide whether to replace the turbo if a chemical cleaning doesn't work or just ship to the local guru for an opinion. The other decision is whether to pull the head to check piston height to rule out bent rods while the engine is partially disassembled vs reassembly and then compression or leakdown test. Thanks
 

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Discussion Starter · #3 ·
Runaway causes

Other than worn turbo seal, are there other causes of a runaway? To do a compression test with the turbo off is there a way to route the oil line for the compression test? Will cylinders hold excess oil after a runaway and is there a way to clear for a compression test?
 
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