Help- Rough Idle, coolant over flow pushing out coolant.
 

My wife noticed while raging and waiting in a fast food line for 20 min. that our 90 190 E 2.6 started to run rough. She also noticed the smell of antifreeze when the aux cooling fans kicked on. The temp was at the line above 80 (Est. 100) I confirmed and was able to make the car do the same a week later. But the problem wasn't showing itself and I went into a wait and see mode.

I just got finished putting in a new modulator and adjusting it yesterday (the bladder was broken and was sending ATF up the vacuum line into the intake manifold), when the above problem came out in force. I changed all the plugs today with Bosh Platinum 4's and changed the air filter (no change). I didn't notice any plug that was cleaner than the others. Two days now it has started rough, stumbles at idle and seems to get worse when hot. My first thought was that I had pulled or cracked a vacuum hose somewhere else on the engine when I rotated the trans. Butttttttt.

The coolant tank started to overflow today after I drove for about 20 min. and was at idle for about 5 minutes. (temp was at est. 100 when it started the overflow). This coolant overflow has got me thinking the head gasket is cracked. I don't see any oil in the antifreeze. The antifreeze hasn’t changed color. I do smell sulfur like smell from the exhausts system that wasn’t present before. No smoke from the tail pipe. I think the Oil pressure is running high at idle-just above 2 while in park, but I don’t know what normal was. Engine stumbles just like a major vacuum leak.

What should I be looking for as to more tell tail signs? Could it be a cracked head? How can you tell the difference? Any suggestions on where to start testing? Will a compression check show anything yet or does the failed gasket have to open up more?

I've Done a post search and read them all, this is my best guess. Please tell me yours.

The way to test for this is with a block tester from NAPA> It goes in the coolant tank and looks for hydrocarbons in the coolant.

Take out those crappy spark plugs and instal Bosch copper core!!!
They are much better and cheaper.

How does the NAPA block tester work? Is it a sensor instrument of some sort? Is it a chemical you pour in and it changes color? Is it a strip of paper?

Just curious to know what's involved.

I just had momentary lapes of reason. THE CONSTANT ROUGH IDLE STARTED AFTER I PUT IN THE Bosh Platinum 4's and progressed to the point of undriveable tonight. It could be that the spark plugs fouled afer about 30 minutes of driving.

Has anyone heard of head gaskets or heads failing in this nature. It was running fine in the morning, change the plugs, runs fine for one trip to lunch, then fails to undrivable by the evening. This still doesn't explain the boil over. But if someone knows of these 4 electrode spark plugs causing problems please let me know. If they turns out to be part of the problem tomorrow I going to be P>O>ed and send those puppies back to BOSH for a refund. I will make sure to repost my results.

Pull out the plugs just to make sure they are not creating any problem (you should not be using these plugs anyway, stick to the factory recomended ones for maximum performance and lifetime) and if they are fine, then get a radiator pressure tester (they sell for about $120, so you may want to rent one or get it done at a radiator shop) and measure wether your radiator system can hold pressure without leaking. If it does not, then go from there to find the leak which may or maynot be the head gasket. But do this pressure test first.

The Platinums are definitely not what you want to use in this engine, but I don't think it has much to do with your problem. I had this same problem with my M103 engine. It turned out to be the cylinder head corroded between the water jacket and combustion chamber above number six cylinder. It happened due to lack of frequent anti-freeze changing by previous owner. I should have changed it when I first bought the car, bud didn't.

If this is indeed your problem, a competent automotive machine shop can weld up the head, and it would, of course, be foolish to not do a valve job, seals and guides at that time.

I'm not saying that this is the problem with your car, because I have not had the opportunity to diagnose your car. But, if the coolant has not been changed regularly, it very well could be your problem.

Testing the coolant for exhaust gas is definitely the place to start your diagnosis.

Best of luck,

If the engine starts and runs ok cold, and the coolant isn't pumping out of the overflow tank, I would not likely suspect a head gasket or other leak between cylinder and water passage. Further, the coolant should not be boiling at 20 psi when you reach 100C!

Is the pressure cap on tight? If so, have you inspected its sealing gaskets? A deteriorated cap caused the problem for us - once the coolant starts boiling, it no longer cools, and the engine is overheating even if indicating 100C.

After replacing the cap, we split a hose, and the others were obviously deteriorated, so I replaced all which are all or part in the engine bay. No further problems.

I would also put in the copper-core plugs, as others said.

Steve

Well I changed out the plugs with new motorcrafts, and the engine shake went away. Or parts guy doesn't carry Bosch Copper core. I'll have to order some. The Bosch P4's lasted 45 minutes until they almost shook the engine apart. Advanced Auto took them back. I drove all day and can't get it to shake anymore.

As for the coolant overflow. I couldn't find a block tester today, my all wise NAPA store guy said, "We ain't got no fancy smanchy tester like that for that Mersadieys Ben$$$$." This guy wasn't firing on all six either. I did notice on the inside of the radiator cap that the inner rubber pressure valve was not seated correctly. It was sort of angled in the hole.

I still smell antifreeze inside the car. Maybe the heater coil has a small leak in it. The smell is intermittent.

Is bubbling in the tank normal when the temp rises? Should the radiator hoses to the water pump be tight with pressure when hot and running. My other cars fill tight with pressure.

The compression today on the cylinders was 170 to 175 on all 6.

Your problem could be, as someone previously suggested, in part due to a faulty expansion tank cap or a bad cap gasket. Try a new one ( not too expensive and always good to have a spare) or have the old one checked and also clean the metal part on the tank opening. The engine may overheat and loose coolant with a faulty cap. Pressure testing the coolant system is the way to go for your problem once you have ruled the cap out. Does you rcoolant have the right mixture? 55%coolant/45% Water is the most coolant you can put in there to ensure optimum cooling and antifreeze qualities of the coolant. Too much lowers to boiling point.
Copper plugs are the way to go!
A sulfur smell in the exhaust may indicate a bad O2 sensor or cat.
You may also try to fiddle with the air/fuel mixture manually to get it absolutely smooth.
Good Luck!
F.J.

Thank you all for the help I will keep hacking away at this. The antifreeze mixture is not something I thought of. I didn't know it lowers the boiling point if mixed to rich. Make sense that lowering the freezing point would do that; physics says something must give. I'll pick up a new cap also.

I'll deal with it when I get back from picking up a 91 300 E 3.0 that I just bought. I got it for a good price $7100 w/116K on it.

I can't sleep, I can't stop thinking about it. These puppies are addictive. This is #2 in my small fleet with many more to come.