Ask Me Help Desk - 1990 Civic losing oil

I have a moderately modified 1990 civic 1.5L with MPFI and recent cylinder head rebuild. It has 190K miles on the block, but during the rebuild of the cylinder head 6 months ago, it checked out [ie no burning oil etc.]

What is going on is there is a build-up of oil residue in the radiator over-flow tank and on the radiator cap. I have flushed the system twice but it keeps getting oil film. Now the strange thing is that of course, I am losing oil but not on the outside of the engine. There is NO water in the oil or crankcase but somehow the oil is going into the radiator... I have never seen this before and neither has the mechanic. The engine performs very strong and is a blast to drive except for the oil in the radiator.

HELP!:confused:

Any leak is always frustrating. However, detecting an unseen oil leak is much worse, especially after a rebuild. My guess is that it's a head gasket sealing issue. There are two main oil returns in the front of the head and two in the rear. Oil is likely seeping from an oil return hole into a cooling passage.

Let me ask a question. Was the head checked for warpage by measuring along edges and 3 ways across center? Using a precision straight edge, resurfacing is required if warpage is not less than 0.05 mm (0.002 in.). Since you didn't have this problem before the work was performed, it's likely related to the quality of the workmanship. I suspect the head is warped. Properly sealing a warped aluminum head is difficult if not impossible.

Used oil analysis might indicate antifreeze in the oil. With that additional evidence, and knowing what work was or was not performed, I would insist that the mechanic fix the problem. Oil getting into the antifreeze affects proper cooling, which could eventually contribute to overheating the head and warping it beyond use. It's your money.

Attention to detail makes a huge difference when rebuilding engines. Did the mechanic apply clean engine oil to the cylinder head bolt threads and washer contact surfaces, before torqueing? Honda normally specifies this. Did he torque per specifications for your specific engine and year? If he didn't do all of this, it might be a simple job to fix the problem.

Thank you txgreasemonkey for your fast response. I do not think the mechanic used clean oil on the thread bolts but I do know that he used the Honda manual to get the correct sequence and torque specs for my engine. Are you saying that if this was not done correctly, there may be a chance to re-torque and that might seal the leak?

As for the cylinder work, I did take it to a reputable machine shop with experience in Hondas. They did the normal rebuild work and they also did a 3 angle valve job and ported the exhaust ports. They also shaved the head about .040" or whatever the max is on that head. The machinist did tell me that if the head was ever to come back off for any other work, that was the last time they could cut it so I would have to get another one. None of this work however, stands out, to me at least as a possible cause to my oil problem.

Just trying to give enough information for an accurate diagnosis.

Quote:

Originally Posted by FLASH_WALL

Thank you txgreasemonkey for your fast response. I do not think the mechanic used clean oil on the thread bolts but I do know that he used the Honda manual to get the correct sequence and torque specs for my engine. Are you saying that if this was not done correctly, there may be a chance to re-torque and that might seal the leak?

Yes. SAE convention is that torque specs are dry, unless specified otherwise. Honda specifies on these engines to lubricate the cylinder head bolts and washer contact surfaces, first, with clean engine oil. Internal and external threads should also be cleaned. You might think this doesn't make much of a difference, but it does. It means your head gasket is probably 25% under torqued! For example, a specification calling for 53 lb.-ft. (oiled) would equate to approximately 66 lb.-ft. (dry). It's all in the thread stretch for a given size bolt, with so many threads per inch.

If you decide to loosen, clean, oil and retorque the cylinder head bolts, use a new head gasket and make sure the engine is "stone cold" first, so as not to warp it. Keep me posted.

I use to have the same problem you have except on a d16y5 block using a po-8 head. When the motor was apart, I resurfaced the head. After my rebuild, I experienced the same symptoms you have. First and foremost, I retorqued the head, drained the coolant, filled the radiator again and ran the car for a little while. The problem persisted. I then just pulled out the headgasket and installed a new one. The problem was solved. Turns out the oil was seeping into the water galleys during operating temperature. In short there was a compression leak. Now the car seems fine but I have yet to test it during hard driving. Another symptom I experienced was bloated coolant hoses. During operating temperature, the coolant hoses were very firm and you could tell that the coolant pressure was way above normal. Hope this helps.