Blown intake gasket ?

[Mike T]

A little while ago I was out pushing the car a little and heard a slight pop (not loud at all) in the intake. Got out of it right away and pulled off at the next exit where I noticed it had a slight miss and was running very rich. Was maybe 5 miles from home and it was late at night so I drove it home. On the way home the miss went away so I figured everything was good. The PL was not recording so I don't have a log to review.

The next morning the car started fine but was still very rich. In checking the basic stuff and found that the water level was down and oh no the oil was a little milky. Assuming one of the head gaskets went I pulled all of the plugs and found them all to be rich with no signs of water. Prior to this all of the plugs had always had great color.

Compression test shows 154-156 cold on all cylinders except for #6 which has 150 and the plug looks identical to the rest of them. Next step was to fill the radiator and pressurize the system with a hand pump. As soon as the pressure came up I could hear water hissing inside of the motor right where #6 meets the intake.

I changed the oil/filter a few times and ran it a little with the belt removed and the water drained to help evaporate the water out of the oil.

I think the chances are low of it being a blown intake gasket but though it was worth asking if anyone has blown one before ?

Thanks,
Mike

 

[TurboBuRick]

I've seen them blow but the car usually goes lean from the huge vacuum leak.

Did you check the vacuum line on the fuel regulator? If it blew off the tune would be rich down low.

Rick

 

[Pronto]

Do a leakdown test. I'm betting the #6 will leak down in short order.

 

[Mike T]

I've seen them blow but the car usually goes lean from the huge vacuum leak.

Did you check the vacuum line on the fuel regulator? If it blew off the tune would be rich down low.

Rick

The vacuum line to the fuel pressure regulator stayed in place. It sure would be nice if was only leaking around the water port in the rear but somehow I don't think I'm going to get that lucky. Did you ever figure out what caused the ones that you have seen to blow?

Do a leakdown test. I'm betting the #6 will leak down in short order.

I will do that next # 6 is suspect for sure because prior to this event all of the cylinders had almost identical compression readings. The bad news is that head gaskets are the graphite style and if one of those turned loose there is probably debris all through the motor.

Without a log I won't know for sure what happened to it but in all honesty I think it may have leaned out due to low voltage. Some of the log files prior to this were showing intermittent low voltage. Why everything went rich after this still has me puzzled.

 

[TurboBuRick]

It was pushed out from boost. The gaskets were fatigued. They were pel fro racing gaskets. The ones that just go on the runners. Non valley pan style.
Needless to say there was a huge vacuum/boost leak that made it super lean down low.


Rick

 

[Mike T]

I may have found what caused the backfire. While pulling the plug wires from the coil pack the #6 terminal lifted right out.

 

[Pronto]

Wow, that would do it.

 

[trixdout]

Dam what a way to blow a hg.

 

[Mike T]

Dam what a way to blow a hg.

It went on the dyno with that same pack and never missed a beat. It's not cracked or damage around the terminal either.
Was still hoping for a leaky intake but everything is pointing back to #6 cylinder.

 

[Nick Micale]

It went on the dyno with that same pack and never missed a beat. It's not cracked or damage around the terminal either.
Was still hoping for a leaky intake but everything is pointing back to #6 cylinder.

Time to replace the old and outdated coil/module with a TR6!

Other than that smart-ass comment, I have one that may help you.

A "few" times dealing with water in the oil, I have drained the oil and not replaced the drain plug. Then pressurize the cooling system to see if water is draining out the pan.

Even though compression in a cylinder is good, that does not mean the head gasket is not damaged enough to pass water.

I have replaced a few 1000 heads gaskets, but very seldom an intake gasket for a water issue.

There is also the possibility of a crack somewhere, but hopefully that will not be in your case.

 

[GNRick]

I've had a couple spark plug related issues but never blew a hg as far as I know. One time the #3 plug broke in half. Heard a loud pop, opened the hood and saw the plug wire dangling, still attached to the plug. Half the plug was still screwed into the head. Another time the #6 plug blew out of the head. Apparently I hadn't screwed it in tight when I changed it last. So are you saying I just got lucky? These were on two different cars.

 

[Mike T]

I've had a couple spark plug related issues but never blew a hg as far as I know. One time the #3 plug broke in half. Heard a loud pop, opened the hood and saw the plug wire dangling, still attached to the plug. Half the plug was still screwed into the head. Another time the #6 plug blew out of the head. Apparently I hadn't screwed it in tight when I changed it last. So are you saying I just got lucky? These were on two different cars.

Yours was probably best case scenario because the compression was release and also there was no chance of the plug igniting at the wrong time.

 

[Mike T]

Time to replace the old and outdated coil/module with a TR6!

Other than that smart-ass comment, I have one that may help you.

A "few" times dealing with water in the oil, I have drained the oil and not replaced the drain plug. Then pressurize the cooling system to see if water is draining out the pan.

Even though compression in a cylinder is good, that does not mean the head gasket is not damaged enough to pass water.

I have replaced a few 1000 heads gaskets, but very seldom an intake gasket for a water issue.

There is also the possibility of a crack somewhere, but hopefully that will not be in your case.

Smart-assed comments welcome here.... if you don't have a sense of humor and patience you might as well find another hobby. Thank you for the advice.