4G93 DOHC Problems

drummydrew

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drummydrew

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Dec 7, 2015
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good evening all, i started asking for advice under Car Talk section but i believe it's more appropriate to discuss real car problems in this section. to cut story short, my car started spitting and rumbling few days ago and sent it in, these are the identified problems as of now:

1. broken valve spring
2. broken inlet valve
3. broken inlet valve guide
4. chipped water vents on the cylinder head (requires welding and sanding according to mechanic)
5. dents on piston heads, caused by what seems like the valves due to the round-edged dents

for further details of discussion please refer to pix attached and link below:

http://www.zerotohundred.com/newforums/showthread.php?t=461048&page=2

my main concern now:
1. should i replace the valve spring/inlet valves/valve guides by the sets of 8 or it is ok to replace just the broken ones?
2. can't find ori parts, will the japanese made oem parts work just as well?
3. i'm totally clueless on the marks on the piston heads

:banghead::banghead::banghead:
 

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vr2turbo

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vr2turbo

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You can just change only the damaged valve. I did that before. Valve guide even taken from another old engine.
Piston ask your mechanic whether okay or not.....
 

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Cheap would be to fix whatever that's broken.

Better would be replace the entire head with everything inside and change those pistons.
 

drummydrew

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drummydrew

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just spoke with the mechanic over the phone and he quoted me about rm2k for total repair cost :rolleyes: my legs went soft straight, that money can REALLY get me a new head. the list roughly includes:

- replace inlet valve x1 (broken)
- replace exhaust valve x1 (bent)
- replace valve spring x1 (broken)
- replace inlet valve guides x8 (1 broken some loose, but need so many?)
- replace valve stem seals x16 (necessary?)
- cutting valve seats x16 (necessary?)
- skimming valve guide :confused:
- weld and sand water vents

pointers please?
 

drummydrew

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drummydrew

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You can just change only the damaged valve. I did that before. Valve guide even taken from another old engine.
Piston ask your mechanic whether okay or not.....
judging from the quotation my mechanic gave me, im gonna be in for a blood fest :bawling:

Cheap would be to fix whatever that's broken.

Better would be replace the entire head with everything inside and change those pistons.
dayum you are right! if the price can't get any lower i may as well start looking for a mivec head :rofl:
 

lsm1991

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lsm1991

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judging from the quotation my mechanic gave me, im gonna be in for a blood fest :bawling:

dayum you are right! if the price can't get any lower i may as well start looking for a mivec head :rofl:
ouch... i would probably look for another head....
 

^pomen_GTR^

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^pomen_GTR^

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just spoke with the mechanic over the phone and he quoted me about rm2k for total repair cost :rolleyes: my legs went soft straight, that money can REALLY get me a new head. the list roughly includes:

- replace inlet valve x1 (broken)
- replace exhaust valve x1 (bent)
- replace valve spring x1 (broken)
- replace inlet valve guides x8 (1 broken some loose, but need so many?)
- replace valve stem seals x16 (necessary?)
- cutting valve seats x16 (necessary?)
- skimming valve guide :confused:
- weld and sand water vents

pointers please?


replace valve (must)
replace valve spring (must) <- install better valve spring if u plan to do more high revving later on
replace valve guide (best is to do all 16...but 8 is enough..since probably some of them also at its limit already)
replace stem seals (must replace all..if not later the old one leak u need to open up the valve cover again and redo that)
cutting valve seat (must..also known as grindvalve)
skimming valve guide?? <--- or was it skim the head? is skim head better check the suface flatness first...then only decide..but if me i will do it in one go since head out already
 

drummydrew

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drummydrew

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RM2k seems on the high side......
that quotation includes:
- remove-cleaning of radiator
- replacing a few hardened hoses
- spare parts (now off the list cos im bringing my own parts)
- workmanship for removing, re-installing, welding, sanding, skimming

i presume it'll be cheaper but will still update price when all is done :shot:

replace valve (must)
replace valve spring (must) <- install better valve spring if u plan to do more high revving later on
replace valve guide (best is to do all 16...but 8 is enough..since probably some of them also at its limit already)
replace stem seals (must replace all..if not later the old one leak u need to open up the valve cover again and redo that)
cutting valve seat (must..also known as grindvalve)
skimming valve guide?? <--- or was it skim the head? is skim head better check the suface flatness first...then only decide..but if me i will do it in one go since head out already
i decided to get my own parts and let him charge on workmanship, just placed order at the spare part shop - replacing the damaged inlet and exhaust valves, all 16 valve guides, valve spring, stem seals and top gasket kit. the rest are procedural work as the mechanic explained to me:

- cutting valve seat
- removing and installing new valve guides (apparently a rigid process)
- weld and sand water holes on cylinder head (marked area in pix attached)

glad that my pistons are still usable but might look into new ones soon enough. after all these is done, should i send my car in for a re-tune? :wavey:
 

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vr2turbo

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vr2turbo

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that quotation includes:
- remove-cleaning of radiator
- replacing a few hardened hoses
- spare parts (now off the list cos im bringing my own parts)
- workmanship for removing, re-installing, welding, sanding, skimming

i presume it'll be cheaper but will still update price when all is done :shot:



i decided to get my own parts and let him charge on workmanship, just placed order at the spare part shop - replacing the damaged inlet and exhaust valves, all 16 valve guides, valve spring, stem seals and top gasket kit. the rest are procedural work as the mechanic explained to me:

- cutting valve seat
- removing and installing new valve guides (apparently a rigid process)
- weld and sand water holes on cylinder head (marked area in pix attached)

glad that my pistons are still usable but might look into new ones soon enough. after all these is done, should i send my car in for a re-tune? :wavey:
The water vents looks like corroded holes.....:rolleyes:
 

^pomen_GTR^

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^pomen_GTR^

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drummydrew

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drummydrew

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Dec 7, 2015
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good evening all, i started asking for advice under Car Talk section but i believe it's more appropriate to discuss real car problems in this section. to cut story short, my car started spitting and rumbling few days ago and sent it in, these are the identified problems as of now:

1. broken valve spring
2. broken inlet valve
3. broken inlet valve guide
4. chipped water vents on the cylinder head (requires welding and sanding according to mechanic)
5. dents on piston heads, caused by what seems like the valves due to the round-edged dents

for further details of discussion please refer to pix attached and link below:

http://www.zerotohundred.com/newforums/showthread.php?t=461048&page=2

my main concern now:
1. should i replace the valve spring/inlet valves/valve guides by the sets of 8 or it is ok to replace just the broken ones?
2. can't find ori parts, will the japanese made oem parts work just as well?
3. i'm totally clueless on the marks on the piston heads

:banghead::banghead::banghead:
(UPDATE) after leaving my car in the workshop for weeks, finally have it back! still got struck with some disappointment though.. basically here's what i did altogether:

1. engine top overhaul
2. replaced engine-radiator hoses
3. service radiator and gasket
4. replaced broken valve spring, broken inlet and exhaust valves, 16 valve guides

i bought most of the spare parts (~RM1k) and left the work to the mechanic and the bill still totaled to about RM2k. means i'm coughing out 3k in total to get these things done :confused:

guess what, the work is not done. picked up my car and found it spitting white smoke! to make it worse, there's a rattling sound coming from the fuel tank :frown: mechanic and i took it out for a drive and he told me that - the white smoke is caused by my worn piston rings but this problem didn't exist before i sent the car in. as for the rattling sound, he said faulty fuel pump :smokin:

this is my car restoration story. attached is a part of the service receipt, tell me what you think!
 

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6UE5t

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6UE5t

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(UPDATE) after leaving my car in the workshop for weeks, finally have it back! still got struck with some disappointment though.. basically here's what i did altogether:

1. engine top overhaul
2. replaced engine-radiator hoses
3. service radiator and gasket
4. replaced broken valve spring, broken inlet and exhaust valves, 16 valve guides

i bought most of the spare parts (~RM1k) and left the work to the mechanic and the bill still totaled to about RM2k. means i'm coughing out 3k in total to get these things done :confused:

guess what, the work is not done. picked up my car and found it spitting white smoke! to make it worse, there's a rattling sound coming from the fuel tank :frown: mechanic and i took it out for a drive and he told me that - the white smoke is caused by my worn piston rings but this problem didn't exist before i sent the car in. as for the rattling sound, he said faulty fuel pump :smokin:

this is my car restoration story. attached is a part of the service receipt, tell me what you think!
Aiyo, then need to do OH again to replace the piston rings leh! Should have done it all in 1 go.
Yah if there's vibration sound from the fuel tank or the fuel line, then it can be the fuel pump assembly is already leaking air bubbles due to o-rings in the assembly not sealing properly anymore. So if this is the case, it's not about the fuel pump motor but the whole assembly/casing is the problem.