RocketSapp

Guys,

I think I might have a blown head gasket on the 89. I have noticed a new noise on the passenger side of the motor towards the front. Sounds like air getting past the plugs but I know they are in well.

I just replaced the plugs on Sunday with Bosch Plats. I was also going to pull the frisbee off, but when I tried it just turned the motor. I stopped and did not turn it any more. I started the car to pull it in the garage and it seemed to be running OK.. When I was driving to work yesterday (Monday) I noticed that it was running rough and did not have a smooth idle.

Today I noticed the noise was really bad. So, I got home and parked it so it could cool down. We jumpped in the truck had dinner and stopped by the parts store. We picked up some Delco plugs for the car and I replace them all tonight.

While I was at the parts store I also picked up a set of ramps that turned out to be the perfect width for the 275s that I have on the car. (had to use some boards to get the clearance though) So, I also changed out the O2 sensor that I had gotten and did not change on Sunday.

Now the car is running great.. Before I was unable to hit it going into second gear and it did it with ease after I was done. However, the noise on that side of the car is still bad. I am starting to think that I have a blown head gasket to the outside. I have not checked the radiator to see if I am getting pressure in it but I don't see anything filling up the over flow tank.


So, now for my quesion.. Would a compression check help to identify a problem with the head gasket? What is the best way, short of pulling the head, to identify the problem?

RocketSapp

65Z01

To loosen the "frisbee" bolts/nuts, lay a pry bar or screw driver across thr front between the bolt heads. Then use that leverage to hold it while you loosen each bolt.

Could the sound be comming from the EGR pipe area or maybe from a blown exhaust header gasket.

A compression testor will show up a head gasket leak. Sears has them for a decent price, with instructions on how to do the testing.

JCAIRE2

Tom Piper

I prefer a leak-down test to a compression test.

Tom Piper

ClarenceT

yes and I preffer a full 180-point inspection of all my fasteners, bearings, seals, a data scan, dyno chart, the aforementioned leakdown, vacuum, and an interview with the rods about how the main bearings are doing

Not everyone has a compressor. Compression check is a lot easier too, no need to find TDC for every freakin' cylinder just to find out if it's indeed an internal seal problem. Do a compression check. then if you find one or two that are low, then you can do a leakdown and find out if it's a cracked block, bad valve seals, rings, headgasket, or whataver.

If it is a HG, then your easiest bet will be two cyls being low, right next to each other. And if that's the case you know it's a headgasket

bogus

There is another test - a little device that tests the coolant for combustion blow-by.

About 30.00 or so.

Tom Piper

I sincerely apologize, this wasn't intended to cause any problems with anyone. It was intended to convey the fact that a leak-down test can be used more effectively at pinpointing a problem, instead of knowing there is one. Unfortunately, since I've had one for years, I forgot that not everyone has an air compressor. Since the title specifically asked about a head gasket leak, I figured that the author wanted it pin-pointed.

Tom Piper

ClarenceT

That sounds pretty damn cool, I wish you knew what it's called I want to look it up now.

Actually I sincerely apologize if it came off as there was a problem

I just think it's a lot quicker and easier (not to mention available) to do a compression check first and was trying to attach a little humor to it.

You want to zero in on the one or two problem cylinders with a comp gauge, then you can start shoving your car around in 5th and screw whistles in and all that good stuff

87NassauBlue

Before I would go to the trouble to start doing a compression test, I'd try to pinpoint the noise more with some tubing. You can take some tubing like a 3/8's fuel line, about 3 feet and stick one end in your ear and move the other end around where you think the noise is coming from. The noise will transmit up the tube. You can pinpoint the noise pretty accurately that way. It it still looks like a head gasket, then you should start fussing with those plugs. There are a number of things that could make that noise, I'm thinking you just disturbed some pipe or cracked a hose some where.

RocketSapp

There is a good chance that I did just that. All of the ERG stuff that is there has been plugged by the former owner. However, when I was running it last night at an idle trying to listen and zero in on it the car was missing and it even sounded like a small backfire or two. It's not really sounding like just an exhaust leak. I still have some testing to do to find out.

--

Bogus, what is involved in testing the coolant for signs of a blow by?

--

While I have done a compression test or two in my past I have never done a lead down test. What does it take to do one? I do have a small compressor here.

RocketSapp

parafrog

a quick way to look for a head gasket leak is to pull the radiator cap off and look for bubbles in the coolant. it may not be definitive, but it's a good quick start.

frog

korvette4u

DO the simple test first.. forget about compression test ,leak down test untill you perform block check test...what is it? Block leak TEST KIT .. it was the quickest easiest way of determining head gaskets failure.. How? if the blue dye turns yellow... repair the head gasket. why? becuz this stuff detects combustion gases in the coollant..

i used it and just finished rebuilding my 89 L98 for that exact problem.. blown head gasket

ClarenceT

Nice link, thanks!

PS. leakdown is the following:

1.Pull out plug
2. Find TDC
3. Screw in leakdown tester
4. pressurize the cylinder
5. watch the guage and see how much pressure the thing is losing
6. if it's losing more then you want, listen for leaks:
ie:
Burbling from radiator - headgasket
Hissing from valve covers - valves
Hissing in crank case - rings
etc

Leak downs take a hell of a lot longer then simple compression tests (like finding TDC on each cylinder for instance, you have to rock it back and forth in 6th gear, or use a button if you have an auto since you're kinda screwed out of the other option) but once you know a cylinder is bad, leak down will actually tell you WHY you have low compression.

SunCr

Most of the head gasket problems on the '89 will be at #8 or #7 and the spark plug will usually tell the story. Look for rust on the threads or just a different color on the electrode then all the rest.

The sound of rushing air probably has nothing to do with it. Suspect the air pump circuit; either the hose to the right header or the line to the cat. A defective check valve can also cause a noise. Remove it and if you can blow air through it in the direction of the radiator, it's defective. If it's a rattling noise, suspect the pre-cat in the front Y pipe on the passenger side.

RocketSapp

This started on Sunday after I got done putting in new plugs. The plugs that I pulled out all looked great. No issues with rust and the tops looked clean. I ran on the plugs since I got the car in Nov.

I don't think there are any pre cats on the car. When I was under it on Tuesday I just saw the Y-pipe going back to the main cat in the middle. The Air Pump was also removed and the ERG tubes that lead into the passenger side exhaust manafold have been plugged off. But I don't think that an exhaust leak would cause the motor to run rough.

Anyone know if AutoZone sells the leak check kits for the coolant?

RocketSapp

SunCr

Make sure the blower motor cooling hose hasn't fallen off. It runs from the housing to the motor.

EGR runs from the rear of the header to the intake manifold. Air pump inlet is at the front of the header, underneath the a/c on the right hand side. A functioning check valve would not have to be blocked off, as exhaust pressure would keep it closed. There is also a line to the cat, with a check valve that functions the same way. Something had to happen to that when the air pump was removed. In any event, if it's leaking exhaust anywhere near the header, it can suck in air and give it a lean miss. A scan might show a Block Learn in the 140's at idle. The other possibility - for the miss - is that a wire got damaged during the plug install.