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Z24 engine best way to disable the fuel for compression test??


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Update with some good news . . . 

 

Took the head down to the local machine shop with the gasket and he identified where the gasket had been leaking but said the head looked ok.

 

He's gonna spin it in the chemical bath and hopefully just skim the face and do the valve stem seals, he recommended getting new head bolts, hopefully have it back by end of week.

 

Now I've just got to clean the block deck. I picked up a razor blade/scraper tool just figuring out how to stop any debris falling into the waterways/cylinders/timing cover, should I block them all up with tissue paper or something? 

 

Also any other advice on cleaning the block would be great.

 

Ta, Rich 

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By '91 it's very possible that the Z24 has switched to TTY (torque to yield) bolts. Once stretched they should be replaced. Older Z24 head bolts were reusable if undamaged.

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11 hours ago, datzenmike said:

By '91 it's very possible that the Z24 has switched to TTY (torque to yield) bolts. Once stretched they should be replaced. Older Z24 head bolts were reusable if undamaged.

 

he couldn't source replacement bolts so suggested they must be reusable

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So I've scraped off most of the old gasket with a razor blade and brake cleaner and wondering what the next best course of action is . . . 

 

I started cleaning the tops of the pistons with green scotch brite but stopped as I read the debris can get stuck in the piston rings (sink between piston and cylinder wall), so I stopped that immediately and hoovered any debris and wiped around with a rag.

 

I was thinking to sand the block deck with a flat block of hardwood and a fine sandpaper but piston 1 seems to be just above the top of the deck so would make it tricky getting around.

 

Also wondering if i can somehow clean the piston rings without turning the engine over as the chain is wedged. 

 

Any ideas? 

 

 

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It is a good idea to sand the top of the block. You could turn the crank about 2 degrees and get the pistons below deck for sanding. I use WD40 to lubricate the paper. It's best to use a wet-dry paper or emerycloth. Cheap hardware store sandpaper can leave actual sand behind which can get down the bores.

 

I wouldn't worry too much about scotch-brite damaging the piston rings or bores. When you're done cleaning the pistons, blow them off with compressed air, and go around the piston (like between the piston and cylinder wall) to help blow anything out of the rings. It's also common practice to flush the junk out with solvent, which will gather in the pan or drip out the bottom of the block.

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On 3/9/2022 at 3:58 AM, Stoffregen Motorsports said:

It is a good idea to sand the top of the block. You could turn the crank about 2 degrees and get the pistons below deck for sanding. I use WD40 to lubricate the paper. It's best to use a wet-dry paper or emerycloth. Cheap hardware store sandpaper can leave actual sand behind which can get down the bores.

 

I wouldn't worry too much about scotch-brite damaging the piston rings or bores. When you're done cleaning the pistons, blow them off with compressed air, and go around the piston (like between the piston and cylinder wall) to help blow anything out of the rings. It's also common practice to flush the junk out with solvent, which will gather in the pan or drip out the bottom of the block.

 

Really appreciate the advice bro.

 

I think it's ok actually having looked again I need to double check my straight edge I think, also I'm worried if I turn the crank at all the wedge will dislodge.

 

Got WD40 on hand will grab some wet and dry paper, which nr you reckon, 240 or higher? 

 

What kind of solvent should I flush it with, and you mean between the piston and cylinder wall? 

 

I'm picking the head up tomorrow it's been fully reconditioned.

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  • 2 weeks later...

Some bad news re the Urvan . . . 

 

So I've been procrastinating over prepping the block deck with soo many contradicting opinions on diff methods and yes or no to using abrasives.

 

In the end I decided to scrape off as much of the old gasket as i could with razor blades and brake cleaner then used an aluminium section with 180 & 400 wet/dry paper.

 

After sanding it back some a few hairline cracks became apparent between two of the water jackets and high/low spots around most of them.

 

After virtually a day of sanding I called it but after putting it back together I have the same problem wildly fluctuating coolant and bubbles/smoke/overheating. 

 

I'm thinking I didn't deck it enough (should of used courser paper) and left low spots between the water jackets and cylinders where combustion is leaking.

 

Final pics of the deck pre-gasket unfortunately not that great quality.  

 

So I'm deliberating taking it apart again and having another go or looking at different block options.

 

WhatsApp Image 2022-03-18 at 1.55.53 PM.jpeg

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I wouldn't worry too much about those. Lots of engines have them and the owners never know it, and they go on to lead happy lives. It's just a surface crack between two water jacket holes. The water's going nowhere. Look at it this way there was stress.... and now it's been relieved.

 

The stains around the water ports on the intake look like coolant may be getting into the openings.

 

The head. Checked for flatness with a straight edge? Aluminum heads can warp if over heated. The most common is a pucker between 2 and 3, a lifting up allowing combustion to blow between, sometimes into the water jacket. A 0.004" feeler gauge should not fit through any gap under the straight edge set along the length of the head.

 

 

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I would think the head bolt is sealed at the bottom (threaded blind hole) and the top has a washer and the top of the bolt clamped at 60 ft lbs.

 

 

 

 

photo_2022-03-19 22.29.15.jpeg

 

There should be a single stud, bottom center of the intake. 10 (ten) bolts with washers, 4 on the top and 6 along the bottom..... what did you take off?????

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4 hours ago, datzenmike said:

I would think the head bolt is sealed at the bottom (threaded blind hole) and the top has a washer and the top of the bolt clamped at 60 ft lbs.

 

 

 

 

photo_2022-03-19 22.29.15.jpeg

 

There should be a single stud, bottom center of the intake. 10 (ten) bolts with washers, 4 on the top and 6 along the bottom..... what did you take off?????

 

Hey Mike . . . re the intake, that sounds about right one stud and 10 bolts (4 at the bottom/middle with washers, the rest through holes in the mani without). 

 

I scraped the mani and gave it a light scrub with scoth-brite but didn't really check it for flatness. Could a leak there cause air pressure/locks/bubbles in the cooling system??

 

The cylinder head is reconditioned from the machine shop. 

 

I'm more sceptical whether I sanded down the high spots on the block deck around the water jackets and combustion gases are getting under the gasket and into the cylinders but I'm far from an expert. 

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I just don't know if it's worth taking the head off again and trying to sand it more by hand, if the deck is warped I'm wasting my time right?

 

I checked it with a straight edge and 0.004" feeler gauge as best i could and it appeared flat. 

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The machine shop would have checked it for flatness.

 

The cooling system is under slight pressure when warmed up. If a leak, it would leak out.

 

 

Didn't you have pictures of the rat's nest of cooling hoses under the intake? Wasn't one or two blocked off?

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3 hours ago, datzenmike said:

The machine shop would have checked it for flatness.

 

The cooling system is under slight pressure when warmed up. If a leak, it would leak out.

 

 

Didn't you have pictures of the rat's nest of cooling hoses under the intake? Wasn't one or two blocked off?

 

I think you've lost me Mike! ha

 

Cooling system is under slight pressure so rather than air leaking in coolant would leak out? That doesn't explain the bubbles coming out the rad neck though? Could combustion/exhaust be leaking into the cooling system from the inlet manifold (warped or not clean enough)? Is it worth me removing just the mani and going over that with block and wet/dry? 

 

Yeah got pics of the cooling hoses under the mani, and your right one was blocked off, but i checked a few other Urvans and they all had the same setup. 

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36 minutes ago, Stoffregen Motorsports said:

There aren't going to be any high spots in the block deck.  The reason for sanding the surface is to give a clean surface for the gasket to bite to.

 

Ah you reckon, but when i was sanding there were clearly spots that were shiny and others still dark, can see in the pics. Especially around the water passages. 

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Posted (edited)
5 hours ago, datzenmike said:

Yes when the cylinder fires the pressure is anywhere up to  1,000 PSI.

 

Hmmm ok so doesn't sound like air could be getting in via the inlet mani gasket then.

 

I'm starting to think maybe it's a minor leak in one of the hoses just I've never noticed a leak, perhaps it's in a hidden spot (like beneath the inlet mani) and not enough of a leak to cause an obvious drip. 

 

I'll run a combustion leak test in the morning to confirm if air or exhaust in the coolant system. 

 

Edited by richURVAN
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Remember the cooling system operates under pressure, a leak anywhere would flow out not suck air in. Bubbles in the coolant is almost certainly cylinder pressure getting past a bad head gasket. Doesn't take much of a leak.

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8 hours ago, datzenmike said:

Remember the cooling system operates under pressure, a leak anywhere would flow out not suck air in. Bubbles in the coolant is almost certainly cylinder pressure getting past a bad head gasket. Doesn't take much of a leak.

 

But isn't the leaked out coolant displaced by air and then you get steam rising up? I read a story exact same as mine on another forum and they went through the same process changing all the coolant ancillaries and gaskets and it was a worn out hose all along.

 

Also I already changed the head gasket. 

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Your pictures from yesterday show it apart. So it's still bubbles?

 

If so with rad cap on, does the pressure build and push coolant out the over flow? into the coolant recovery bottle?

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3 hours ago, datzenmike said:

Your pictures from yesterday show it apart. So it's still bubbles?

 

If so with rad cap on, does the pressure build and push coolant out the over flow? into the coolant recovery bottle?

 

Hey Mike,

 

Still bubbling yeah.

 

Just had another attempt at bleeding it;

 

1) Drained both the rad and block 

2) With bleed valve out (located beneath thermo housing) refilled the rad until water starts flowing out 

3) Re-fitted bleed screw and continued topping up rad (prob got about 6 litres in plus whatever the reservoir tank holds)

4) Started engine with a no-spill funnel in the rad neck 

5) Watched as water level fluctuates by up to 1 litre in the no-spill funnel and seemingly pressure wants to escape out the rad neck from somewhere then it starts bubbling and steam/smoke arise

6) Turned off the motor drained some of the water then stuck the combustion leak tester in the rad neck while pumping the ball on top of it 

7) Steam/smoke enters the tester and no change in colour so a negative result for exhaust gas!?

 

I'm about to try (with the rad cap on and thermo out) just fitting a garden hose to one of the heater hoses to pressure fill the system and unscrew the bleed valve to force any air out.

 

We'll see if pressure builds and pushes coolant out the over-flow. Does this all look right with the reservoir set-up?

 

 

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another clue maybe? Some kind of staining on the back of the thermo, I've read that people have a lot of problems with thermostats not opening/sticking and often drill that hole . . .

 

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Bleed valve? Got  picture? only thing under the thermostat housing is the temperature gauge sender.

 

Thermostat isn't going to cause bubbles.

 

Doesn't the combustion tester sample the coolant? If so you have fresh water in there. You may have to run the engine for some time to contaminate the liquid and produce a reading.

 

Yes, seal it up and let it warm up. See if anything is pushed out into the overflow container.

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1 hour ago, datzenmike said:

Bleed valve? Got  picture? only thing under the thermostat housing is the temperature gauge sender.

 

Thermostat isn't going to cause bubbles.

 

Doesn't the combustion tester sample the coolant? If so you have fresh water in there. You may have to run the engine for some time to contaminate the liquid and produce a reading.

 

Yes, seal it up and let it warm up. See if anything is pushed out into the overflow container.

 

You can see it in this pic, the screw with the cooper-eze around the thread, the temp sender is on top of the thermo housing.

 

But if the thermo was stuck (not functioning as it should) coolant might not circulate and cause overheating / boiling / bubbles. 

 

The combustion tester sucks in gases from the rad neck while you pump a ball on the top but your right maybe I didn't run it long enough but I fear for the new head and gasket running it while it's effectively overheating! 

 

Gonna pressure fill it now with the hose.

photo_2022-03-21 14.10.10.jpeg

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