(partial) compression test

[MrTibbs]

Thought I'd share this, I've gone past the p*ssed stage and can laugh at the situation.

On the way home from work I thought I'd treat myself to a new toy - a compression tester. I go out to the car, remove the spark plugs and DME relay and screw the tester into no1 cylinder. Get my girlfriend to crank the car for 5 seconds while holding the accelerator to the floor.

Compression on no1 (in a cold engine, with no oil in the cylinders) was 160, so that seems pretty good.

Time to move onto cylinder no2...... hold on, the tube won't unscrew from the spark plug hole. The tube twists but the part that screws into the hole can rotate around the tube and isn't turning at all. Maybe it has flats on it to get a socket or at least screwdrivers onto it - nope that would be too easy. Wasted about half an hour with screwdrivers etc trying to get the thing out but no luck.

Thought of a variety of things I can do tomorrow when the shops open:
Needle nose pliers (possibly filed down to fit in the limited clearance)
Superglue something to the fitting that I can twist
See if some garden or fuel hose will slip over it enough to twist it

An internet search reveals I'm not the first idiot to do this - in addition to the things I'd though of above, people recommend yanking it really hard while twisting; warming the engine up by running on 3 cyclinders for a bit (sounds plausible); or cutting the hose and hammering something in that'll grip the fitting (a bit like an easy out).

Anyone have any other ideas? or want to guess which of these will work.

I'm thinking try the hosepipe trick 1st, then if that doesn't work warm the engine. Then onto the needle nose pliers route. Then who knows. Don't really want to trash my brand new (and not the cheapest) comp tester having only tested 1 cylinder).

Might write to them suggesting they write some kind of instruction or hint on the packaging saying it might be an idea to use the extension - I'm sure a lot of people know to use it but it seems a bit of a harsh way to learn.

Mike

[vdubr928]

Find us a pic of the product you purchased. Mine has a box end at the base. Like a 13mm.

I think in the end I would try to heat up the head a little somehow. That should break the tension a little and you can pull a little and back it out.

[Dan Himan]

Maybe carefully heat the area with a propane torch, low heat, slowly. Ever use a easy out, there is a extractor to remove the heater outlet for chevy trucks, its about 3/4 to 7/8 thick at the base, 1/4 at the tip, and reverse threaded.

[rick13]

Take some pics. You did the right thing by walking away. Take your time and think it through. No torches eh ...?!!!

[MrTibbs]

Here's a pic.

It definitely doesn't have any flats or anything else you could get a socket, wrench etc on. It's completely round, and the hose isn't fixed solidly to it, it can rotate within the end piece (I have no idea why, as the gauge can rotate around the tube too).

It's not in there very tightly (only got it in there by twisting the tube, which then started to spin inside the end piece) so I think the main challenge is to get something to grip it. I'm actually thinking heat won't really help much - am wondering if superglue is actually the best tactic - I could try to get some needle nose pliers but tools always seem to be the wrong dimensions in cases like this.

I really don't understand why they don't make it with flats to help get it out it you do put it in a deep recessed spark hole.

Mike

[rick13]

Yeah, maybe a dab of epoxy at the seam would keep it from spinning. Good luck and let us know your results.

Rick

[djnolan]

if the braided hose is twisting on the fitting, and it is a recessed spark plug you are hosed!

Can you squeeze the hose at the fitting with pliers while trying to loosen it? Add a little WD-40?

Otherwise can you yank the hose off the fitting? Then you can use needle nose or shove a screw driver down the center to unscrew it? Once removed I am sure it can be repaired (ie jb welded) for use on a non-recessed spark plug port...

Cheers!

[Aufenbahn]

Mine does that sometimes but if you wiggle it - pull, push trying to unscrew it eventually it will come loose - I think

[mikepellegrini]

Originally Posted by Aufenbahn

Mine does that sometimes but if you wiggle it - pull, push trying to unscrew it eventually it will come loose - I think

+1 I've got essentially the same guage and it should come loose. You put it on hand tight.

One other possibility might be to reach down in the hole with a very thin screwdriver and try to turn the fitting a bit. Make a very small turn and then it oughta come off easily by hand.

[vdubr928]

If you can get any bite with a flatblade you might be able to chisel it counterclockwise.

I long pair of forcepts might get you in there.

Same with a long but thin pair of needle nose.

Heat always helps. Expand the cylinder head thus loosenig its grip on the brass.

Some kroil oil will do magical things.

Worst case..... cut the line and chisel it out with a chisel. Two taps straight down to bite then angle the chisel as much as you can and tap it counterclockwise.

Follow these steps.

1. Have several beers before bed.
2. Wake up refreshed saying out loud over and over "there is no way im going to let a compression tester kick my a** "
3. Go fix car and next time use the correct socketed extension included in your kit.

Im not being mean. This is what I do when im getting my but kicked by something that should not be this hard and it works everyone so far.

[MrTibbs]

Thanks guys,
Got up this morning and remembered I had some long nose pliers in a drawer somewhere (I'd forgotten about them).

They couldn't really grip it very well as the hose was in the way, but I could get one of the prongs/noses to touch the side of the fitting and the other one to put a little bit of pressure on the other side. it kept slipping and I was about to give up when I thought I saw it move a tiny bit. Another 5 or 10 minutes of trying and it definitely moved.

I now have it off the car. The tester came with a solid tube with a rubber fitting on the end; you have to hold it in the spark plug hole so can't do the test on your own, but I think I'll use that for the rest of the test.

I think I'll write to the manufacturers to suggest the make the fitting with some flats or notches to help if people do get it stuck (or that they include some instructions saying the hose might spin in the fitting).

Might file some flats into the fitting in case I want to use it again (though I'll be wary of that. Or maybe epoxy it so it won't spin.

Right - when my girlfriend gets back from the gym I'll test the other cylinders.

Mike

[MrTibbs]

Ok, so I used the solid tube attachment. You have to hold it down quite hard, but I wasn't really up for using the hose again.

The numbers (with a cold engine, all plugs out, no oil in the cylinders) are:
1 - 160
2 - 175
3 - 160
4 - 160

Think I might have done no 2 slightly incorrectly, as not sure why it'd be higher than the others. In any case, for an 86 924S I think these look OK. At least I know I don't need to do a head gasket job.

I do however have a chirping front end, and I get a whistling sound at around 3k rpm, so I'll need to check the belts and rollers today (replaced the belts about 2k miles ago, so will check tension and see if one of the rollers is on the way out - didn't replace all of them as some of them looked pretty new).

Mike

[vdubr928]

Awesome. The beer helps. Lol

Those numbers are great. No way to do a test wrong and get a high reading. Its not abnormal to have a high cly. Just because you have good compression does not mean head gasket is not leaking. They can spill water into the cly and not be bad enough to show on compression. Even a leakdown test can miss a small head gasket failure. Did you have missing coolant? That is the only sure way.

Either way. On a cold motor those are good numbers. Looks like plenty of life left.

[MrTibbs]

No missing coolant or anything. Didn't suspect a blown gasket, just thought I'd do the test out of interest to see what the results were.

Generally the motor seems pretty strong - I've done 2,500 miles since changing the oil and it's not needed a top up, so seems leak free. The exhaust gasket is blowing a bit, but I might put on the exhaust from my parts car - the headers look in better condition.

Just re-tensioned the belt as well and all seems good - the chirping noise I was getting was just the alt belt.

Mike