As the title states, I recently changed my head gasket ('99 420a). I spent hours and hours researching, posting my questions to the forums, and buying all the recommended parts*. I got everything back together and started the car.

It started great and idle was very smooth. It was rough before the head gasket change but I think that was just because the throttle body was full of oil. The car was sitting in a heated shop at about 55* and nothing visible was coming out of exhaust pipe. After about three minutes, vapor came out nearly as bad as before I changed the head gasket.

The smoke continued. I couldn't clearly tell if it was white or blue. It seemed like a pale blue but the shop walls are white so it's deceiving. Since the repair, the engine has been running for a total of 40 minutes idling and putting around at no more than 25mph with some slight revving to see the smoke level increase.

I did everything by the book for this head gasket change. I love the car and will keep it for a long time so no short cuts were taken!

From my preliminary research, I am considering a few scenarios: 1) problem with piston rings due to overheating before head gasket was changed, 2) coolant still sitting in catalytic converter and muffler but will vaporize after a few days of driving

I changed the head gasket because it seemed to be the problem to me, a shop diagnosed it as the problem, and because 420a's are known to kill head gaskets.

What is your advice? Thank you very much for reading this! I really appreciate the help!

* Because I know someone will ask, I used a MLS gasket with copper coat and replaced the head bolts which I torqued to MLS standards.

Have you noticed anything in terms of oil consumption? I know you only recently changed the head gasket but keep and eye on your oil. If its consumption is high maybe an issue with your valve stem seals? Ever had them replaced? How is the smoke on a cold start say overnight and first start in the morning?

Every 3000 miles it needed a 1/2 quart of oil or so (head gasket had been getting worse and worse for awhile). The previous owner said it was just the head gasket leaking (shop told her). I hope it wasn't really the valve seals. Valve seals have never been touched. I had a machinist inspect the head when it was off and he said everything looked good. I haven't driven the car out in the cold yet since I don't want to harm anything and I have another car to drive.

If you are absolutely positive that you did a correct replacement of the head gasket you may want to start considering your valve seals. Go for a short drive? Your ECU may throw a code and tell you the problem.

A proper leak down test will tell you what you need to pursue next(should have done first). Points to valve stem seals or rings...or you can just keep sticking oil in it.

You said you did everything by the book so I presume you had the head checked for warpage?

Originally posted by bullettdsm
You said you did everything by the book so I presume you had the head checked for warpage?

Yes, I had it resurfaced, pressure checked, and inspected. I took it to NAPA and an older guy did it for me. He seemed very knowledgeable. I asked him a few times through our conversation if he found anything odd at all with the head and he said it looked great, especially for 176k.

Originally posted by RallyEclipse98
I took it to NAPA and an older guy did it for me. He seemed very knowledgeable. I asked him a few times through our conversation if he found anything odd at all with the head and he said it looked great, especially for 176k.

There's your problem right there! You can't trust those old farts for nothing :P

Ok, next up; did you check your oil? Any milky stuff?

Originally posted by bullettdsm

Originally posted by RallyEclipse98 I took it to NAPA and an older guy did it for me. He seemed very knowledgeable. I asked him a few times through our conversation if he found anything odd at all with the head and he said it looked great, especially for 176k.

There's your problem right there! You can't trust those old farts for nothing :P Ok, next up; did you check your oil? Any milky stuff?

When I drained the oil prior to the head gasket change, I swashed it around the drain pan and it looked good.

I only checked the oil after the car had been running and smoking for a few minutes. Looked fine.

Originally posted by Slo2g
A proper leak down test will tell you what you need to pursue next(should have done first). Points to valve stem seals or rings...or you can just keep sticking oil in it.

A reputable shop that the previous owner took the car to diagnosed it as the head gasket. I thought no further investigation was needed.

Oh and after I drove the car for a few miles and it was up to temp, when I revved the engine, it was spewing out what appeared to be anti-freeze.

No CEL. Only light on the dash after the install was the SRS light on for some reason,

If its spewing coolant, seems like you probably have a bad head gasket(didn't seal properly) or a cracked block...

you need to do a few tests before throwing more parts at the car. I would do a Block test first to see if there is any HC in the coolant then from there a pressure test on the cooling system then a leak down test.

original It was sounding like valve stem seals but if your pushing coolant out the back you have bigger problems than that, you said it overheated before? how hot did it get?

Originally posted by Socal420aT
you need to do a few tests before throwing more parts at the car. I would do a Block test first to see if there is any HC in the coolant then from there a pressure test on the cooling system then a leak down test. original It was sounding like valve stem seals but if your pushing coolant out the back you have bigger problems than that, you said it overheated before? how hot did it get?

Well I bought the car with the problem so I don't know how hot it could have got with the previous owner. However, she had a nearly all highway commute and the car didn't heat up too fast so I doubt it got too hot. When I've owned the car, the needle only creeped up past 1/2 way twice, both times for just a minute or two.

And when I drained the oil and coolant the first time, they both looked normal. The coolant jug definitely had no signs of oil contamination.

After speaking with the shop further, I was told they inspected the valve guides as well. They checked out okay.

Still haven't had a chance to get to the car in person yet.

I still haven't had a chance to check the compression on the engine but I did see the car for a few minutes yesterday. I looked under the engine and right beneath the front cross member is a small puddle of oil. Didn't get a chance to investigate. I'm scared though because I don't believe there's a simple fix for an oil leak in that location!! Perhaps I do have a cracked block for the head gasket didn't seal right. I just worked so hard to get everything perfect I'm a bit sad now.

This past weekend I went home and was able to do a compression check with a good quality compression tester (FYI O'Riley's rental compression testers are terrible).

My numbers: 190 190 190 190

The numbers should read from 170 - 225 with the variation no greater than 25%. The car has 176,210 miles and the battery I was using was pretty weak so my numbers could be higher if I put a new battery in the car.

I took her for a short drive but I will put some miles on her as suggested. My educated guess is that the cat and muffler still have anti-freeze in them and that's why when the car gets warm it smokes white. The exhaust heats up and vaporizes the liquid.

Thanks for the replies to this thread! If the smoke remains after a few hundred miles I will update!

Didnt work b/c it wasnt the headgasket causing the exhaust smoke to begin with!!! Did u ever think that oil is getting into the cylinders by slipping past the valve seals??? Ahhh!!! U need to do a lil more research next time. Time to pull it apart again. U should just do everything right this time while its apart,oil seals, piston rings, some crower 2 cams, hint hint, lol!!!