Head Gasket thickness

[jeepinblackdog]

I have a 2003 jetta ALH motor that has been completely rebuilt(new rods, pistons, valves) by a local engine builder and I only have 405 psi on each cylinder. It smokes a lot during cold start up (its around 0 degrees here right now) but then smooths out and runs fine but does not have the power it had before and I'm getting low 40 mpg. I have the timing set just below the green line and I have set the IQ to max power. I also have new 1019 injectors and a new vnt17 turbo. also have a karma tdi tune.
My question is this. I originally had a 2 hole head gasket in it and I noticed it now has a 3 hole gasket Could a thicker gasket cause the lower psi (I'm thinking it should be around 550) I have put around 2k miles on it since the build.
Any input would be greatly appreciated.

 

[IndigoBlueWagon]

How did your builder choose a three hole gasket? If it was from measuring piston protrusion, and if he was accurate, then the gasket may be correct.

How many miles on the rebuild? It takes quite a while for rebuilt TDIs to get to full compression and power. I have about 4,500 miles on mine now and it's waking up, but it has more to go. And the new engine in my wagon is running strong now, but it took 50K miles to get there.

 

[jeepinblackdog]

Im not sure how he selected a 3 hole. When I ask him, he didn't know and was being very vague. I didnt tell him how because I thought he knew how. That's why I questioning his work. He works on mostly gas motors. Should have done it myself.....So back to my original question will a thicker gasket make a big difference in Compression pressure. I only have approx 2500 miles on the rebuild.

 

[KERMA]

Been a while since I calculated this, but going between 1 hole to 3 hole is something like +/- 30% volume difference at TDC. That's a lot! Going from 2 to 3 is less so but yes it is still significant. And it WILL cause issues like you are experiencing. If anything I like to tend toward the smaller head gasket. For example in my beetle it was on the lower side of the 2 hole spec so it has a 1 hole gasket.

I am a firm believer that THIS is one of the main reasons, if not THE reason some cars are such strong performers and smoke free and 50+ mpg while others are dogs that get 34 mpg and smoke like crazy, with no obvious differences between cars. If the piston protrusion is not dead even across cylinders then the discrepancy causes low compression in some of them relative to the others which is a less than optimum situation.

Also have encountered a fair amount of anecdotal evidence that most TDI rebuilds don't turn out quite as well as could be hoped. They are never quite like the engines were when they were new. I believe this may be because many of the machine shops do not use the correct cylinder honing technique when they prepare the block. This is a point of contention among forum folks but I have seen too many instances of those kinds of problems for it to be something else.

 

[IndigoBlueWagon]

I'd probably do a compression test on a known good ALH with your tool and see what you get. Compression testers show some range in readings, so 405 may be OK with your tester, may not be. Hard to tell without a basis for comparison.

If a known good engine shows, say, 450, then I'd drive yours another 5K miles and test it again. If it's coming up keep going. If it doesn't change you can pull the head, measure piston protrusion, and choose the correct gasket.

EDIT: Kerma posted just as I was, and the honing comment is a good one. My local guru has changed his honing equipment to help shorten break in time. And the rebuilt engine on my Golf, with aftermarket rods and rod and piston assemblies balanced, runs smooth as can be, equal to if not better than the 50K mile factory long block in my wagon. It can be done very well, with the right parts and skills. But often, as Charlie points out, that's not the case.

 

[pdq import repair]

I have known so called mechanics the say they always put in the thickest gasket "to be safe" I have called their bluff everytime and asked them what projection they have and they can never tell you.

As far as honing goes, unless you do a rebore there is absolutely no reason to rehone the cylinder on a simple re-ring. Often you can still see the original hone marks.

 

[turbovan+tdi]

I like IBW's advice, wait a bit more and recheck. 400 is low. If the head and deck weren't touched, no need for a 3 hole gasket BUT was said, the piston protrustion does need to be checked.

As far as honing goes, unless you do a rebore there is absolutely no reason to rehone the cylinder on a simple re-ring. Often you can still see the original hone marks.

False economy not to hone. I've read time and time again some say not to hone with new rings, so I tried it one day and just as I thought, had blowby and crappy ring sealing. Don't play games, hone the cylinders with new rings.

 

[IndigoBlueWagon]

New rods could change piston protrusion, depending on what they are. Pistons may not be exactly the same as originals, either. That's what I was thinking. When I put Integrated rods in my wagon head gasket went from 2 to 3 hole. Compression was fine.

 

[jeepinblackdog]

Thanks for all the response! It kind of confirms what I was thinking. It had a 2 hole on it before and I had about 590 psi except for number 3 which was low. Hence the reason for the rebuild, (Bent rod that eventually broke) I had 405 when I 1st rebuit it and it is still 405 after 3k miles so I think when I have time I will pull the head and check protrusion and order the correct gasket. I did put new rods and pistons in but I dont think they measured it before ordering the gasket. Who knows It might need a 1 hole now. It is a real dog with last tank only getting around 35mpg with winter blend and being minus temps here now It does not want to start very well and smokes a lot for the 1st 30 seconds then smooths out and quits smoking.

 

[Fix_Until_Broke]

A rough rule of thumb for an ALH with stock geometry is each 0.001" of piston protrusion is worth 0.1 points of compression so each range of head gasket is worth ~0.5 points of compression

If you had 590 psi on the same compression gauge before and are at 405 now under the same conditions (warm engine, charged battery, all GP's removed, etc), then you've got a bigger problem than a 2 vs 3 hole head gasket.

I'd check to see that the cam/crank is in time. If you're retarded by a tooth on the timing belt (or a couple on the flywheel), it will cause low cranking compression because the intake valve is closing 15+ degrees late so that air is gong back out the intake valve. This will also cause hard starts in the winter.

Do you have sooty intake ports in the head if you pull the intake manifold off?

Check out this thread - a little over the top for your specific application, however has the info you're looking for.

 

[jeepinblackdog]

A rough rule of thumb for an ALH with stock geometry is each 0.001" of piston protrusion is worth 0.1 points of compression so each range of head gasket is worth ~0.5 points of compression
If you had 590 psi on the same compression gauge before and are at 405 now under the same conditions (warm engine, charged battery, all GP's removed, etc), then you've got a bigger problem than a 2 vs 3 hole head gasket.
I'd check to see that the cam/crank is in time. If you're retarded by a tooth on the timing belt (or a couple on the flywheel), it will cause low cranking compression because the intake valve is closing 15+ degrees late so that air is gong back out the intake valve. This will also cause hard starts in the winter.
Do you have sooty intake ports in the head if you pull the intake manifold off?

Check out this thread - a little over the top for your specific application, however has the info you're looking for.

When I put it together I triple checked the timing and it was all good. What do you mean by .5 points of compression for every hole size? you lost me on that.

 

[Fix_Until_Broke]

Every 0.001" of piston protrusion is worth ~0.1 points of compression (roughly). If you had the correct piston protrusion for a 2 hole gasket and put a 3 hole gasket in, you will have added ~0.005" of head gasket thickness (or reduced piston protrusion relative to the head surface by 0.005") which will reduce your static compression ratio by ~0.5 points, from 19.5:1 nominal to 19.0:1 with the thicker head gasket. This will reduce your cranking compression a little but, but not ~200 psi as you're seeing.

If you're confident that your cam/crank timing is spot on (ie, Are you sure your flywheel mark is correct?, Did you double check it with the front of the crank marks?, Did you check it recently after it's been run?), the next thing I'd look at is the cylinder head.

Pull the valve cover - are the cam/lifters in good shape?
What was done to the cylinder head during the rebuild?

I've pulled a "new" cylinder head out of the box, filled the ports with brake clean solvent and had 6 of 8 streaming out of the valves. The cylinder head supplier assured me that this was fine and they would seal up within a few minutes of running the engine. This was related to my question about sooty intake ports. If the intake/exhaust valves are not seating correctly you'll have sooty intake ports (assuming you have EGR delete), poor cold start, low power/economy, etc. This is what happened to the engine I put this cylinder head on. 1 intake port was clean, 2 were really sooty and the third was a light dusting. This corresponded to which valves streamed solvent from them. All the rest of the symptoms were there as well, hard, smokey start when cold, poor economy, etc.

Do you have any more details about the engine rebuild - what was done, what was not, etc?

 

[turbovan+tdi]

I've pulled a "new" cylinder head out of the box, filled the ports with brake clean solvent and had 6 of 8 streaming out of the valves. The cylinder head supplier assured me that this was fine and they would seal up within a few minutes of running the engine. This was related to my question about sooty intake ports. If the intake/exhaust valves are not seating correctly you'll have sooty intake ports (assuming you have EGR delete), poor cold start, low power/economy, etc.

What a moron, arg, I hate people that say stupid things like that or are that dumb they actually believe that crap.

 

[jeepinblackdog]

I must clarify that this is a new block as well, due to the #3 rod breaking and creating a window on each side of my old block. The only thing that is from the old engine is the head and crank. The head/valves was checked (by the builder) and deemed good. The head only has about 30k miles on it as I replaced it with a new head from Odissa out of florida. when the old head had a valve seat let go and destroyed the head. The crank was turned and check for straightness. So the 590 psi was not from this block.

 

[pdq import repair]

Do a leakdown test to determine engine sealing values. A good engine will be less than 10%. I trust leakdown testers, not compression testers. They all seem to vary.
If you have leakage you can hear where it goes. If you have good leakdown and low compression on a proven gauge, off with it's head.
I would check compression on a good running rig with that gauge just for calibration before I went any further.

 

[Macradiators.com]

Anybody has the selection table for the 2.0 CR engine? Euro version 16.5 CR
Thanks!

 

[turbovan+tdi]

Do a leakdown test to determine engine sealing values. A good engine will be less than 10%. I trust leakdown testers, not compression testers. They all seem to vary.
If you have leakage you can hear where it goes. If you have good leakdown and low compression on a proven gauge, off with it's head.
I would check compression on a good running rig with that gauge just for calibration before I went any further.

A compression test is good for a baseline, then take it a step further with a leakdown.

Leakdown varies, I've seen it range from 10-20% and still run good.

 

[Fix_Until_Broke]

Can you elaborate on who did what in the engine rebuild process?

It sounds like you did the camshaft/injection pump install and timing, but your mechanic did the rotating assembly and cylinder head install maybe? I don't know that any of the below questions will directly relate to the problem you're having, but their answers will help us to better guide you as to what to do next.

Did he replace the main, rod and head bolts upon reassembly, and use the proper assembly sequence (torque + angle)?
Was the new block machined at all?
You mentioned that the crank was turned - mains? rods? - were they just checked or were they turned down?

 

[Vince Waldon]

I must clarify that this is a new block as well, due to the #3 rod breaking and creating a window on each side of my old block. The only thing that is from the old engine is the head and crank

Just clarifying, in case it saves you a wild goose chase, that you understand that this new info means all bets are off, in terms of comparing your old head gasket to your new headgasket

The right headgasket to use is determined by piston protrusion alone. Piston protrusion is a function of the block deck height, the rods, and the pistons...to the one thousandth of an inch. It sounds like at least two of the three factors have been changed.

One other random thought: there's a thread somewhere with the math.. but IIRC if you work out the numbers on a 1.9 litre engine with 20ish to 1 compression you'll likely see that switching from a 3 hole to a 2 hole can't cost you 75-100 psi out of a possible 500ish. IMHO if you're still thinking the wrong head gasket is the cause of 400 psi out of an expected 500 psi you *are* potentially chasing a wild goose. 'Course they *are* tasty, and it is the Holidays...

 

[jeepinblackdog]

I dont have a leakdown tester but when I do the compression test it stays above 400 for at least 30 seconds and very gradually goes down. Yes you are correct I did the timing, but the engine builder did ground the crank to within .001 of straightness and put all new main and rod bearings in. yes new head bolt and I have to assume he did the correct tightening sequence.

 

[jeepinblackdog]

He also said he milled the head flat took off less than .003. I ordered new head bolts and a 1 and 2 hole head gasket in prep of changing them but still not sure that is the problem.

 

[jeepinblackdog]

When talking about leak down what do you mean by the percentage is it a percentage of leakdown over a given time?

 

[turbovan+tdi]

When talking about leak down what do you mean by the percentage is it a percentage of leakdown over a given time?

No, you have 2 gauges on the tester. Generally you put one gauge at 100 psi, that's how much air is going into the cylinder, the other gauge shows what's left. So if you have 90 psi showing, you have 10% leakdown. You can listen to where the air is going, ie tail pipe, air intake or remove the oil cap and listen for air escaping.

 

[jeepinblackdog]

Pulled the head, Had a small oil/coolant leak on backside of no 4 piston and when I loosened the head bolts the 2 bolts between no 1 and 2 and 3 and 4 seamed to break loose easier. Maybe not torqued correctly. Measured protrusion and I have .96mm or .038in protrusion. Definitely needed a 1 hole. Also had a lot of carbon buildup on top of pistons. Any thoughts?

 

[Vince Waldon]

Lots of carbon on the tops of pistons suggests lots of carbon on the sides of the ring grooves... which do a lot of the sealing.

Always tough to talk about an engine without being right in front of it, but 'twere it mine I might pop the oil pan and then pull the pistons... much easier to clean when out and then you can do a full inspection, measure bore wear, ring wear, etc etc etc.

You may be able to refresh the engine with a light hone, carefully cleaned piston ring grooves, and new rings... all do-able with the engine in the car.

 

[pdq import repair]

Dry or wet carbon on the pistons?. Is there any washing of the carbon from the piston edges? If so it is oil washing up from the rings. If it is just dry carbon with no washing it is probably fine, just fuel burn residue.

What was the leakdown prior to teardown? And if it leaked too much where was it going? If piston washing and excessive leakdown into the bottom end then it needs rings.

Stick in the right headgasket for your protrusion upon reassembly. torque correctly and be sure to blow your holes first and lube the threads lightly.

 

[jeepinblackdog]

The engine has less than 3000 miles on it, has new rings, pistons, rods, bearings. It just had low compression (405) across all cylinders and was a dog and was only getting 35 to 40 mpg. It would pump up to 405 within 10 strokes and took well over 2 min to get below 200. I dont have a leakdown tester. I think the builder didn't check protrusion and put the wrong gasket on it. Had a 3 hole now has a 1 hole. protrusion was .96mm. It was dry carbon buildup.. Just finished torquing all the headbolts correctly.Time to time.....

 

[Vince Waldon]

Fingers crossed for you... unfortunately I can't see the head gasket making 50-100 psi difference given that the vast majority of the combustion chamber is internal to the piston... but hope to be proven wrong.

 

[turbovan+tdi]

Pics of the piston tops please.

Check your valve sealing using brake cleaner.

I bet you had timing belt mistimed and bad rings.

 

[Johnny_tdisport]

I've done de compression test on my 2.0 ASV and it have 25bar(363psi) with a 3 hole gasket. I think it's a bit low so i want to try reach de 29 or 30bar. I'll take the head of and confirm, But i remenber that have like 0.00 mm of postrusion of the piston over the Block because they were machined.

At the time of the engine assembly i as concerned about the valve clearence because of the 272* Dbilas camshaft, só i've put the 3hole gasket.
Now i want to check the valve clearence to install the right head gasket.
My question is what the valve clearence gap that should exist between the piston and valve?