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Engine knock after rebuild

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9 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCHEngine knock after rebuild

Reported or suspected cause

coil, thats good

Suggestion or failed attempt

No successful repair reported for this finding.

0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context

Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.

Discussions that suspect a cause
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suspected cause · Original poster

Just noticed one of the coils has a small crack on a side, put it back in but no metal cover on top to see if it makes any spark to the engine and the knock is gone, so the problem was coil, thats good, but the other thing is the coolant bleeding, engine gets to the 180F but front 3 rads is still cold, thermostat (LTT) is opening at 160F, probably there is still some air pockets (new water pump)

Original post Read captured discussion
Engine knock after rebuild
Frequently discussed work

Fill tool and do it right

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion

Don't play around with air pockets in the cooling system, especially on a new engine, get the vacuum fill tool and do it right.

Original post Read captured discussion
Engine knock after rebuild
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Leading evidence: 'coil, thats good' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'coil, thats good' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Fill tool and do it right' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.

Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.

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1 matching discussions · 9 captured posts examined · 0 partial discussions

Compare 2 other evidence results

Fill tool and do it right

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context

Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.

Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion

Don't play around with air pockets in the cooling system, especially on a new engine, get the vacuum fill tool and do it right.

Original post Read captured discussion
Engine knock after rebuild

Use vacuum bleeding tool (airlift)

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context

Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.

Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion

Highly recommend using vacuum bleeding tool (Airlift).

Original post Read captured discussion
Engine knock after rebuild
Frequently discussed actions (2)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Fill tool and do it right

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion

Don't play around with air pockets in the cooling system, especially on a new engine, get the vacuum fill tool and do it right.

Original post Read captured discussion
Engine knock after rebuild

Use vacuum bleeding tool (airlift)

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion

Highly recommend using vacuum bleeding tool (Airlift).

Original post Read captured discussion
Engine knock after rebuild
Reported and suspected causes (1)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

coil, thats good

No successful repair reported for this finding.

0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that suspect a cause
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suspected cause · Original poster

Just noticed one of the coils has a small crack on a side, put it back in but no metal cover on top to see if it makes any spark to the engine and the knock is gone, so the problem was coil, thats good, but the other thing is the coolant bleeding, engine gets to the 180F but front 3 rads is still cold, thermostat (LTT) is opening at 160F, probably there is still some air pockets (new water pump)

Original post Read captured discussion
Engine knock after rebuild
Coverage and how to read this overview

Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.

9 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

  • Rennlist: 1 discussions

0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.

0 acknowledgements have no verified action link; they do not establish a repair result.

Generation: 20261026T122219Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

Hi everyone, just had a engine rebuild with new iron sleeves and new wossner pistons Porsche 996 3.4, engine done only probably 10 miles after rebuild as I still have other things to do to interior and paintwork, all was good until I decided to fit low temp thermostat, filled up coolant, started the engine to bleed the air, revved probably 5 times and started to hear knocking sound temp did not past 180F. Did I scored cylinders again? Oil pressure is all fine.

POST 2Original post

Quotes source post: 16810446

If you are comfortable starting it again record the noise for about 10-15 seconds and post here. There are some here with educated ears. However , if the engine was built by a shop I would flat bed it back to them without restarting. Knocks in a rebuilt engine is not normal!

POST 3 / ORIGINAL POSTEROriginal post

Just noticed one of the coils has a small crack on a side, put it back in but no metal cover on top to see if it makes any spark to the engine and the knock is gone, so the problem was coil, thats good, but the other thing is the coolant bleeding, engine gets to the 180F but front 3 rads is still cold, thermostat (LTT) is opening at 160F, probably there is still some air pockets (new water pump)

POST 4Original post

Quotes source post: 16810549

Highly recommend using vacuum bleeding tool (Airlift). If not, carefully follow the workshop bleeding procedure.

POST 5Original post

Air pocket left in the coolant can cause a big problem, don't ask how i know....

POST 6Original post

You had me really concerned for you with your title "Engine knock after rebuild'. I had envisioned the wrist pin circlip coming loose which is always a concern of these engines. Having heard thousands of knocking noises I would never confuse a wrist pin knock to a coil misfire/sound in person, but when just reading text "a knock is a knock".. Don't play around with air pockets in the cooling system, especially on a new engine, get the vacuum fill tool and do it right. It is a simple and marvelous tool that should have been Invented 40 years ago. We could have really used it on the early 70's Pantera, a 351 Cleveland mid-engine with radiators up front and a PITA to get air pockets out of the system..

POST 7 / ORIGINAL POSTEROriginal post

I will do a vacuum refill today, just one question, is it middle rad should heat up same as the side rads at the same time or later?

POST 8Original post

If you lift the back end of the car so that the tail light are about waist high, the coolant system will self bleed for sure.

This is a source reference. Confirm exact model applicability in the original material.