What everyone above said above. I would like to add that you should do an oil change and start off with the proper oil level. When troubleshooting an issue like this you want to make sure you have all the conditions correct. This means you should also make sure you have bled the coolant properly. Once you have done the above steps check again and see what happens.

As far as the Random no start. Is it a crank no start or no crank at all? I dont think the 2 issues are related. I would focus on making sure the engine was built right first.

 

New or rebuilt engine should have specific oil in it. Which should only be changed at the proper interval. Might not be a special "break in" oil but for a new S2000 your owner's manual specified "Do not change the oil until the scheduled maintenance time." What oil is in this engine is anyone's guess though.

-- Chuck

 

Everything I'm seeing here points to coolant in the oil for sure, likely a failed HG. The shops response is full of shit. It's a generic reply, trying to alleviate any responsibility. There is plenty of red flags here to make a good shop want to investigate further, not just pawn it off as normal nothing to see here. Do not run the engine anymore adding to the risk of scoring the cylinders. Tow back to the shop and have them take accountability for investigating and fixing.

 

^ Terrible response from the shop. If they intend to stand behind that engine in any way, they should want to inspect it based on what you said. It would be much cheaper for them to bite the bullet now and investigate/fix a leaking head gasket than wait for it to overheat and warp the head/block.

I think you should drain the oil and find a way to measure water content in the oil. You'd probably want to flush a few quarts of dino oil through to get the water content out of the engine and leave it sit with fresh oil to prevent rust. Don't run it but you don't want it sitting with water in it. The test would likely confirm the suspicion of water in oil. Once that is confirmed, you'll need to decide how to proceed. The shop should stand behind it but I'd question if I want them working on my stuff anymore. Your other option is to find a hopefully better shop, cut your losses, and pay them to do a proper head gasket job. Then you have to hope the first shop did a good job building the engine in the first place.

 

Oil analysis for water or other coolant in the oil depends on the oil being at engine temperature when the sample is pulled. But... I'd not start this engine again until I knew what was going on. If it was my car it'd be transport to and sitting at the engine "rebuilder" shop not my home. If it was my car.

-- Chuck

 

I agree but the way I look at it is if something is bad inside its over with. You cannot troubleshoot it otherwise. It sounds like he is out of luck based on the shops response and he needs to get to the bottom of this. I managed many shops. The unfortunate truth is that problem cars often get shoved to the side for weeks on end till business slows.

 

Goes without saying, to save some of the oil in case you need it for a lawsuit. I would have someone witness its removal and seal it in a container.