Blown head gasket?

[2000bonny]

I am having a bit of trouble diagnosing my rough running, coolant loosing bonny. I have a 2000 bonneville SLE with 176k on it.
Yesterday on my way home from work the temp guage climbed to about 230 and then started to hear a faint ticking. As I accelerated, it would get more prominent. Then finally it stalled. I coasted to a stop and the coolant in the reservoir was boiling. The upper hose was empty and hot as hell. I added water to the radiator and sterted the car. An extreme amount of white sweet smoke billowed from the exhaust. There is no milky appearance at all to the oil. The ticking sounds like an air leak of some sort coming from the passenger side of the engine, but hard to pin point. I had it towed home at tried adding more coolant with the engine off. Using the air gap at the top of the thermostat housing I kept adding water, and it kept disappearing. I started the car, and it sound like all the water made it to the exhaust system. The car will idle very rough and the belt tensioner is bouncing.
I have read in this forum about this possibly being an issue with the UIM or LIM. Does anyone have any direction to point me in?

[GTP Dad]

Unfortunately you will need to replace both the head gasket and the upper and lower intake manifold gaskets. When you overheated the engine the head gasket blew that is why you got the white smoke from the exhaust. With 176K miles I suggest that you replace rather than repair the engine. It will be less expensive in the long run. I suggest contacting Ed Morad at moradpartscompany.com for a used engine. He specializes in GM parts and his prices are reasonable. Also, I wouldn't drive this car due to the water in the oil as you may destroy the bearings further and need to be towed home.

[Tech II]

12 year old car with 176K, is decision making time.....how much money do you want to put into this?

If the car is in good shape, with no tranny problems, then the cost of an new engine may be worth a few years to you instead of new car payments....

However, if you think the cost is not worth it, you can take a gamble......if this just happened within a few days, my guess is the upper plenum leaked.....chances are your exhaust is full of coolant from this.....It's possible the head gasket is ok, and no coolant got into the oil.....it's also possible there is a head problem if overheated(plus age of engine), and oil/coolant has mixed, which could cause other problems in the not to distant future...that is the gamble.....

You might get away with this: disable fuel and ignition...remove the plugs....crank engine and force coolant out of the cylinders, will be messy.....change oil and filter.......remove the rad cap and upper hose from thermostat housing...lower hose into a bucket to catch coolant....remove upper plenum.....you will probably find lower plenum full of coolant...vac it out....remove throttle body from upper plenum....you will probably find plastic faillure where the EGR stovepipe passes through the upper plenum hole...this is where the coolant leaks......now another decision.....stop here and replace just the upper plenum....or go further and replace the lower intake gaskets......then another decision, the head gaskets.....

I would gamble on just the upper plenum, if money is a factor.....replace the upper plenum, gaskets, themostat, and PCV valve.....replace coolant.....crank the engine again with the plugs out.....replace the plugs.......leave fuel disabled.....crank vehicle several times....then enable fuel.....may have to jack the front of the engine up, to help rid the coolant in the exhaust through the weep hole in muffler.....then try to start vehicle....once started, there might be an air pocket and the coolant will have to be burped.....then change oil and filter again....

To gamble or not, that is the question....

[2000bonny]

I removed the intake plenum and observed one of the o-rings in the gasked was damaged. It appears to have been allowing coolant to pass through on the driverside nearest the throttle body. There are two ports in the top of the intake approx 1/2' diameter. This is just in front of the EGR. Could this be the culprit that had caused me coolant in my exhaust? I have found absolutely no evidence at all of coolant in the oil.

[GTP Dad]

Yes it can be the issue. Do a compression test on the engine while you have it apart to see if all the cylinders are good. If they are not you already have half of the engine torn apart and you can continue on to replace the head gaskets. You may want to consider it anyway since you are so far into the repair.

[2000bonny]

I had just replaced the UIM gasket, pulled all plugs and #4 and #6 were very wet. Turned over the engine to remove all the water. Installed 3 new plugs. I started the car and still ran rough. After a minute or so I pulled the dipstick and found there to be water in the oil now, which was not present before. I removed the intake manifold and see the #4 cylinder rockers are very clean and all others are black. Both sides of the lower gasket are in very bad shape. I cannot remove the exhaust manifold crossover pipe in order to remove the head. What are my chances of this being contained to lower intake manifold gaskets?

[GTP Dad]

The chances are good that the LIM gasket is bad and caused the water in the oil. It probably occurred when you removed the upper gasket. Be sure to change the oil after you replace the gasket. Before doing anything do a compression test on the engine to see if the head gasket is bad. This will save you a lot of grief and time if you have to pull it apart after replacing the LIM gasket.

[2000bonny]

I went ahead and got the head removed. I found a 1/2" section of the gasket gone between #4 and #6. I replaced new gasket and torqued all bolts correctly. I got everything back together and flushed the oil and coolant. I started the car and no longer overheating. I am now showing a code of #4 misfire. I do not notice a difference while running with the plug connected or disconnected. I have spark and even replaced the coil pack. No difference at all. I am going to perform a compression check on all cylinders, but afraid of the results. I also replaced all the plugs. Any ideas what the problem may be?

[GTP Dad]

Check an make sure you got the injector wire properly connected that the signal is getting to the injector properly. You can use a noid light that is available at Autozone for a reasonable price. It is also possible that the wire to that cylinder is bad.

[2000bonny]

I haven't checked the injector signal yet, but I can tell you that the car runs fine down the road. The stumbling only happens at idle speed. I am picking up a light to check the injector this evening. Thanks for all of your insight and suggestions.

[GTP Dad]

Check for a vacuum leak while you are checking the injector. Also you may want to remove and clean the Idle Air Control Motor if you have poor idling. (Just don't move the pintle while you have it off of the car.)

[2000bonny]

I am really scratching my head now. I checked the injector signal with a noid light and it appears to be good. I removed and cleaned the Idle Air control motor. Replaced the plug and wire, installed a new injector, installed a new coil pack, and still idles rough. Runs great down the highway though. Any other ideas????

[GTP Dad]

Check the PCV valve it may be plugging up or sticking.

[2000bonny]

I feel as though I am chasing my tail. Just prior to the car overheating and blowing the head gasket, it ran and idled great. Now it is running really good but idling rough, but not stalling. This has got to be related to the overheating issue I had. I could not get a very good compression reading when performed. The #4 cylinder is in the center back of the engine. I managed to thread the hose in by hand but not very tightly. I only got a reading of 30. I removed and installed on one of the front cylinders in the same manner, and got the same 30psi reading. I know it should be more like 180 or so, but being loosely installed, I think that severely impaired the reading. I have checked coil pack, replaced plug, wire, injector, and checked injector signal with noid light. Removed and cleaned the idle control motor. I am going after the PCV this morning. Would the MAF sensor cause this? When cleaning the intake I removed this, and the casing came apart exposing the chip inside. There was alot of builup and cleaned with carb cleaner and noticed very small connecting wires inside, but too small to verify if I damaged them. I put back together using a small amount of silicone to seal it. I am only getting the misfire on the #4 cylinder though.

[2000bonny]

I mistyped. It was actually the MAP sensor, located above the PCV valve. Would this create the problem I am having, if this is defective?