Need help from the FM mechanics

[lotsofish]

Alright, well I'm a mechanic by necessity, not profession or training, so I'm seeking the opinions of the real mechanics for this one.

Long story short, this weekend I did the following repairs on my 97 Grand Prix with the 3800 non-supercharged engine.

* Replace lower intake manifold gasket - Was leaking coolant into oil.

* Replace the "heater bypass elbow" (black plastic elbow that goes from the LIM to the idle tensioner on to the heater core) - Was cracked and causing an external leak.

* Replace the temperature sensor, because I broke the old one taking the intake manifold out.

* Replace PCV.

* Change the oil.

I replaced both the upper and lower manifold gaskets about 3 years ago because it was leaking coolant into the oil then. This time I believe it was because of the leak from that elbow that caused the coolant level to get too low, the engine to get to hot, which melted the stupid plastic gasket.

After I finished the repairs, the external coolant leak is fixed and so far no water in the oil, but 2 things that are "weird".

1) The first thing I noticed was a high idle speed. It was idling about 300 rpms high stopped in park, driving down the road and letting it coast it was as high as 1500 rpm (barely have to touch gas at 40mph) and driving at 40mph and put into neutral went up to 2200rpm.

Strange thing about this is after driving it about 25 miles, it seems to have fixed itself. On the way home from work today and I just took the boy to scouts, it wasn't idling high at all. I'm not sure why it did this at the beginning and it's not now, but as long as it doesn't start idling high again, I'll consider this "fixed".

2) Low coolant light wont go off/temperature gauge lower than normal. I filled the radiator with coolant and also filled the reservoir to the top. After driving it a while, about 1/3 of the reservoir bottle got sucked in. The coolant light is still on. The coolant is circulating the system though and the heater blows out hot air.

The temperature gauge reads lower than it used to, probably 2-3 lines less than it did before. If it was only this, I would just say it's the difference between the stock temperature sensor and the Checker replacement part I used but because the low coolant level light wont turn off, it worries me a little.

I thought maybe air in the system, so I opened up the air vent on the thermostat housing just a little when the engine was hot to see if any air came out, and coolant came out right away. Where is the low coolant sensor located anyway? If there is an electrical connection, maybe I missed it or it's loose. It's not part of the temperature sensor, is it?

If I can't get the low coolant light off, I can live with it. It does seem to be working properly, coolant is flowing through the system, the hoses are good and tight, heater blows out hot air, and the engine doesn't seem like it's running too hot, just the light wont switch off. Oh, I did try resetting the computer by leaving the battery unplugged overnight without effect.

Thanks for any ideas.

[Hafnutz]

Fast idle problem going away was probably due to IAC (idle air control) relearning itself, should be ok.

Low coolant sensor is in bottom of coolant reserve tank. Common problem. Not hard to change. 3800s are hard to get all the air out of. Be sure to crack air bleeder on t-stat housing and leave it cracked for a few minutes when engine is hot. Temp gauge problem may be due to using aftermarket sensor. I wouldn't worry about it.

3800s are one of the best engines ever made. 200,000 plus is easy to get with a little maint.

[Macgyver55]

The low coolant sensor is in the coolant reservoir. They have a tendancy to stick when low. Usually after filling, a few taps on the tank with a rubber mallet is all it takes to pop it loose. I've never had to replace one yet!

[lotsofish]

OK thanks. Well if it's in the reservoir, then it's definitely a false reading as I can clearly see it's more than half full. When I had the leak it did go completely dry, so it might have had some junk dry on it or something. I'll see if I can reach it without removing the tank and bang on it a bit and loosen it up or try your rubber mallet method. I've had the coolant reservoir out before, but I couldn't remember that's where the sensor was. The airbox has to come out to remove it, but that's all so it's not too bad.

Now that I have this figured out, I can focus on the next thing...

I've had a rough idle for quite a while. Engine codes are set for sticking EGR pintle and occasionally for lean fuel, which should be related. Car has not had any problems starting, gas mileage is the same as it's ever been, the engine still has plenty of power and once you start driving it's perfect, just a rough idle when stopped. I was thinking I would have to replace the EGR, but since the problem isn't that bad I just haven't had the desire to spend the 150+ bucks on it and I don't know if that would completely solve the problem or not. I've tried looking at junk yards and none of the ones I've called keep an inventory of used EGR valves. I could probably find one at a pull your own parts type place, but I haven't gone looking. I just read that you can possibly clean it with brakekleen or MAF cleaner so I might have to give it a try.

The wife says "When are you going to get rid of this thing and get something that runs better?" I actually went looking at some vehicles the other day and it kinda felt like cheating. My poor baby only has 164K on her, and although she's not much to look at anymore, I don't think I could sell her off to someone else or put her to a premature death.

[Jeremy airjer W]

Coolant level sensor is in the radiator not the coolant bottle. If this where a grand am it would be in the coolant bottle. It is a little square black box looking piece that has a couple of wires going to it. I can't remeber what side of the radiator it is on but if you look at the tank about 1/4 of the way down you will see it. It is possible that an air pocket in the sensor is causing the light. You can try tapping on it with the plastic end of a screwdriver to try and get it out.

A vacuum leak would cause a ruff idle and lean codes. That may be worth investigating. If the EGR was stuck open a little bit it could cause the symptom also. One thing you can do to check if the EGR is stuck open is to start the vehicle (cold start) and feel the metal tube that goes to the EGR, if it is open the tube will get very hot (I couldn't tell you how many times I have burned myself on these so be careful.

[lotsofish]

If I take the EGR valve off, there is the round thing in the middle (the pintle, correct?) is that suppose to move if I push up on it? I had it off once and if I remember correctly, it was basically stuck closed. I wasn't really sure if I was supposed to be able to move it by hand or not.

It was a while ago that I had the codes read, but I do remember one of the codes was P1406 EGR Valve Pintle Position. The other one was a P0171 I believe. I agree, there might be a vacuum leak somewhere too. I think that P1406 makes it pretty clear that something is wrong with the EGR. When I tried disconnecting the EGR connector the engine ran the same as when it was connected.

Most likely source of a vacuum leak if there is one? Somewhere in the lines or connectors? What's the best way to try to find a leak if there is one?

[Macgyver55]

Airjer is correct, (again) it is such a common problem on the Grand Ams that when I read the original post my thoughts went immediately to that. My mistake, it is on the radiator. From what I remember, this sensor is wired opposite of what you would think, in that the light will go out when it is unplugged. This should indicate either a bad sensor or a short in the connector or harness.

[Jeremy airjer W]

The only driveability problem an EGR will give you is a ruff run to no idle symptom if it is stuck open (and a stiff brake pedal if it is open far enough). If it does not open you will likely not experience any problems. Its normal position is closed and it is supposed to only open at moderate acceleration and steady cruise. The other sympton you could experience if the EGR is not opening is ping under acceleration. EGR is used to help control this.

As far as checking the vacuum leak you can use a can of carb spray. I would use extreme caution if using this as I have started a few engines on fire and lost some eyebrows doing this. A better way is to use a smoker. Its a machine that injects smoke into the intake under a slight pressure. All you have to do is look for the smoke on the outside and you found the source of the leak.

[Jeremy airjer W]

I was thinking about this at work today and thought I would mention that (I now it's to late for you) we have started using Audi/Volkswagen gasket maker for these types of jobs (intake valleys, oil pans, tranny pans, T-chain cover, etc.). It is a greyish white RTV type of meterial that we have found is for superior to any of the other RTV's (Pick your color black, blue, orange). It is expensive but it works far better!