just installed a jdm d15b engine in my car and, cranked it wouldnt start then we did a compression test and cylinders 1 and 2 had about 150 each, 3 and 4 were like 40-50. Took head apart head gasket looks fine. Can a head gasket be bad even if it looks good??Any suggestions would help. thanks.

 

anything would help.

 

need to fix asap guys.

 

If the headgasket was gone it would probably show low number on all cylinders. You probably have a problem with bad rings rings or maybe bent valves. Just buy a new headgasket and put it on and test it again to see if it works. If it doesn't change anything its no big deal because your going to have a new one when you put the motor back togeather when you fix the actual problem.

 

one way to see if you have a blown h/g...open radiator cap when doin c/p test...see if coolant bubbles...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AF-b16a1 &raquo;</TD></TR><TR><TD CLASS="quote">one way to see if you have a blown h/g...open radiator cap when doin c/p test...see if coolant bubbles...</TD></TR></TABLE>
hmm never heard that

 

bent valves or bad rings would be my guess...any history on the motor or how many miles?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EKchump &raquo;</TD></TR><TR><TD CLASS="quote">bent valves or bad rings would be my guess</TD></TR></TABLE>

im with him

 

jdm engine so roughly around 50K miles. took head apart this morning and putting the 8 valver back on . getting another d15b and fixing this one.

 

jdm engine so roughly around 50K miles. took head apart this morning and putting the 8 valver back on . getting another d15b and fixing this one.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18bEG &raquo;</TD></TR><TR><TD CLASS="quote">
hmm never heard that
</TD></TR></TABLE>

think about it there is no where for the compression to go...if you have a blown h/g it has no where else to go(unless you have bad valves or rings)...so that air has to go somewhere

 

im guessing rings. anyhow i have bad luck with engines. 5 killed with this one in a year

 

rings

 

headgasket would be a more likely cause. headgasket crack between cylinder 3&4. when #3 is being compressed, the air/fuel will leak out into the crack into #4. vice versa when #4 is being compressed.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AF-b16a1 &raquo;</TD></TR><TR><TD CLASS="quote">one way to see if you have a blown h/g...open radiator cap when doin c/p test...see if coolant bubbles...</TD></TR></TABLE>

This only works if the break is to the coolant tubes, unfortunally if you have a bad gasket to the oil like or between 2 cylinders then it will not work.

The best way to test for valves is to use a cylinder leak down test.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AF-b16a1 &raquo;</TD></TR><TR><TD CLASS="quote">one way to see if you have a blown h/g...open radiator cap when doin c/p test...see if coolant bubbles...</TD></TR></TABLE>

good trick

another good one is put a teaspoon of motor oil in the effected cylinders and do the c/p test again if the numbers raise any then its you piston rings.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Syner-G-Racing &raquo;</TD></TR><TR><TD CLASS="quote">

another good one is put a teaspoon of motor oil in the effected cylinders and do the c/p test again if the numbers raise any then its you piston rings. </TD></TR></TABLE>

Yes given you need to do compression numbers at normal operating temp.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BatuKing &raquo;</TD></TR><TR><TD CLASS="quote">

Yes given you need to do compression numbers at normal operating temp.</TD></TR></TABLE>

it will work with cold temperatures also, simple fact that the oil helps to make a better seal, if the numbers were low and you add oil, then the numbers look better, 90% chance its the rings or a warped cylinder etc. ...which your comment brings up another point that a lot of people overlook...do a c/p test cold and record the numbers, then bring it up to temperature and set it up quickly to test again....compare the cold numbers to the warm numbers to better understand the integrity of the rings in question.