I have a 99 Civic EX, Automatic, 4 door, with ~186k miles. About 6 months ago, a technician found oil in my radiator overflow cup. I was due for a radiator flush, so I got the flush done and the car was fine for some time. Just a few days ago, the same problem resurfaced. I had just had an oil change a few days before and the tech did not notice any oil in the radiator overflow, so it appears to have started back up rather abruptly. I know that this era of Accord can have a porous block issue, but I haven't seen that about Civics. Head gasket seems most likely (or possibly automatic transmission/radiator issue, since on some Civics, the AT fluid can run through the same lines, in my understanding), but in any of these cases, why would it stop happening for 6 months?

Other points:
-Car gets oil change every 3.5-5k miles.
-Car has a slight oil leak, has lost about 1 quart a month for the last 2 years, which isn't worth paying to fix IMO, there is a spot on the bottom of the car that is where it appears to be where it's leaking from.
-Had an issue with cyclic revving/sputtering (engine would sometimes rev up and down by about 1000 RPM) pretty badly over the summer, worst when any sort of air was running (A/C or heat) and when idling, attempted a clean of the idle air control valve and it mostly went away (I couldn't quite easily access it, so I didn't do the best job, but it has only happened occasionally since the cleaning and seems very minor now).
-Occasionally it feels a little jerky, like it has a hard time shifting or something, from time to time. This is really minor, but seems worth mentioning.
-Oil seems fine, is not milky, and does not appear to contain radiator fluid.

Do any of you experts have any thoughts on this? I'll be in grad school for another year and a half or so, so I'm really hoping to make this last until I'm out of school. Thanks in advance!

 

99 EX doesn't have a shared radiator (at least, not according to the parts diagrams I'm looking at).

A compression test, as well as a block test would help rule out (or verify) a damaged head gasket. Compression test is free, just have to rent the tool from your local parts store. Block test tool can be rented as well, but the dye you'll need will cost ~$20-$30. You can find DIY's for both procedures in the FAQ's sticky.

 

Thanks so much for the quick reply! For the block test, are you referring to a porous block problem? Is that known to happen with this era of Civic, or just Accords? They are different engines, right?

 

Oh, and regarding those tests...

The cylinder test will show a discrepancy between cylinder pressure if there's a leak in one of them, correct? I didn't see anything regarding the block test in the FAQs. Is there another name for it?

 

I'm not really an Accord guy, so I can't speak towards this porous block problem, but I've never heard of it on the Civics. Completely different motors though.

The leakdown test will measure how much pressure is building up in each cylinder individually during the compression stroke. If one or two cylinders are leaking, that can point towards a head gasket problem. It isn't definitive, but it's a quick test that will start you in the right direction.

Hmm, I thought there was a block test DIY in the FAQ's. My mistake. The block test basically checks your coolant for exhaust gasses. If you have exhaust gas in your coolant, your head gasket is blown. Here's a DIY video off Youtube.

 

i've never seen it happen to a d series motor. it is a problem with 06's, but that is a completely different story.