Hey everyone, i have searched for hours for possible answers to my problem with so far no luck. If i have overlooked a previous search my apologies.

I have a 98 S70 2.3L Turbro. I did a head gasket change and put everything back together. Few problems at first, Couple Vacuum lines broke, unconneted. - Fixed all that and than was trowing a code for the Engine Coolant Sensor and along with that the expansion tank was overflowing (under pressor)- just sneaking out of the tight cap somehow.

I replaced the sensor yesturday and let it run for a long time today. The tempature was staying where it should be and the coolant seemed to be circulating the way it should be.

Sorry to get off topic, but i wanted to fill you in on the history of how i got here.

Like i mentioned the car is running well besides there is a "popcorn noise" is the best way i can explain it. Not somthing thats every "10 seconds" or every "30 Seconds" but random. It will "pop", than 10 seconds later "pop", than 30 seconds later "pop". I read a thread on the CAT being clogged and that could cause the "popping" sound as air comes back into the engine instead of out he exsaust and when the Air coming back to the engine hits the exsaust, causing the "pop". But my CAT does not get that "glowish" red color when its running and its not throwing a code.

I thought it could be an exsaust leak causing air to come into the system, doing the same thing as a bad CAT would do, but i took the Exsaust Mainifold off, inspected for cracks, ensured the gaskets were posititioned correctly, ect.

Put everything back together and still have the "POP" It is driving me crazy. Also - the car does not idle good until it gets warm. I have to keep on the throttle for it to stay running. But as soon as it gets warm it idles on its own fine.

Any feedback would be great - thanks in advance.

 

You didn't say...

1. Does it "pop" when going down the road or just sitting still?
2. If going down the road, then sounds like CV joints; esp if when turning.
3. Does it smell of Orville Redenbacher? Sorry; couldn't resist
4. Does the engine warm up promptly (temp gauge get to 3 oclock position)?

 

The Noise is coming from the Engine - 100% certian. It is obvious when sitting still, and it could be making the noise when i drive it, but can not hear it due to wind, road noise, ect. Not certain if its coming from directly over the engine where the Cams are, or if its more towards the rear of the engine towards the exsaust manifold.

The Engine warms up gradually. I would have to say its average warm up time. Once it is warmed up the temp gauge stays center for the entire time the car is running.

Does the exsaust leak idea sound like a possibility? I dont even want to say it, but could it be a bent valve?

 

Hmm; sticky valve(s) occurred to me too.. rough idle when cold could also be a symptom. I would ck the compression; if that doesn't tell you anything then you could record the noise for us?

Doesn't sound like exhaust leak; that noise would increase in volume with engine load; i.e. louder when going up a hill, etc.

BTW: have you double ckd the cam belt timing?

 

Cam belt timing is good to go. 100 % Certian on that one! i did it over and over and over again to make sure it was 100%. Compression is good aswell.

I will try to record the noise in the morning for you guys.

Just an update though - Tonight i replaced the Spark Plugs, Wires, Rotor Button, and Distributor Cap. Drove it for about 20+ Miles over an Hour. Overheated on me once on the trip (about 40 min in). Pulled right over, turn it off let it sit for 10 min, started it back up (temp gauge was fine) and continued on my way with no other overheating problems. Check engine light went on after that overheat and was saying "Misfire cylinder 5) But that is from the overheating im pretty sure.

After the overheat the coolant resevior was overfilling slowly. But i'm guessing its cause i'm running only water in it and its getting hotter than normal. And that i need to flush the radiator out a few more good times from the "oil/water" mix thats still stuck in there after the blown head gasket.

Does all my "theories" sound like im not too far fetched?