98 TDI Build

[vwishndaetr]

So after some thinking, I think this might be better suited here rather than on Vortex, plus I think the TDI knowledge goes way deeper here, and I already have questions.

Picked up a 98 TDI, 250k, for $1,200 back in September.

What I knew going into it, the exhaust was janky, and the suspension needed some serious work - control arms were bent, amongst other things.

Anyways, brought it home with the good 'ole 3/4 ton rig.

I actually drove 4hrs for this thing. eek.

Engine was surprisingly clean for 250k.

Got it up on jackstands and started taking apart the suspension.

 

[vwishndaetr]

Some of the carnage from the suspension tear down. Bent tie rods, CV joints torn, bent control arms, wheels and tires are toast. Even the driver side fender is toast from the wheel being jammed into the wheel well.

Even the heat shields behind the rotors were bent, which I presume means that at some point the car either fell off some jackstands or it was laid on the ground without wheels. Ehh, what a pile.

[/IMG]

Pretty much everything from the wheel wells is out. Once the engine is vetted, I'll start ordering parts and the suspension bits will go back in.

 

[vwishndaetr]

After some diagnosing I knew the waterpump needed to get replaced, it made some noise and the pulley was walking all over the place. Then I discovered more items and figured if I'm going to get this deep into it then I might as well do the timing belt. Then I thought about it some more and figured I just pull the engine and trans out and do what I need to do.

Nice refresh no?

Removed the front rad support/rebar assembly to give me more space. I like space.

Almost there.

That's it.

Check out the sick exhaust. Gainz with a "zee".

I'm starting to think the diesel was driven off a cliff.

Noticed the transmission mount bracket wasn't parallel to the trans. Sure enough the case is cracked in two spots. This is getting better and better.

Pretty much where I'm at. I got the trans separated from the engine and the engine on a stand for some work.

 

[Mongler98]

that K&N oil filter... OMFG

thnis triggers me 10x more than that epic exhaust... IMO that exhaust is actually awesome and not even one HP was lost...

 

[vwishndaetr]

Which, all of this bring me to my first two questions.

1) What is the best way for me to check compression in each cylinder? If compression is good I won't bother taking the block apart.

2) I broke this when I was removing one of the clamps to remove the hose from it... Barely put any pressure on it and it gave out. Looks like it just collects vapors from the PCV? If my memory serves me right brake booster and other vac lines came to a junction before the spot where it broke.

 

[vwishndaetr]

that K&N oil filter... OMFG

thnis triggers me 10x more than that epic exhaust... IMO that exhaust is actually awesome and not even one HP was lost...

It's late so didn't want to put all the boring details in here, but I was genuinely surprised to see G12 coolant in the car. At least the little bit that there was... This car is literally the definition of doom. When I come around to the interior I'll show the screw driver that is jammed into the clock spring to keep the wipers from running continuously.

 

[Mongler98]

take glow plugs out and jump the starter while on the engine stand, one at a time check compression.. does not rock nearly as much as you think when only 1 is compressing at a time...

grantged you would probably need to set her down into a few tires to connect the trans. IMO if you have a spare trashed trans laying around you can basically make your own bell housing, i did so i could do exactly that..

 

[vwishndaetr]

take glow plugs out and jump the starter while on the engine stand, one at a time check compression.. does not rock nearly as much as you think when only 1 is compressing at a time...

grantged you would probably need to set her down into a few tires to connect the trans. IMO if you have a spare trashed trans laying around you can basically make your own bell housing, i did so i could do exactly that..

Is there a reason I can't just turn over the crank by hand? I was doing it earlier this evening... There was some resistance of course but I was still able to do it no prob.

 

[Mongler98]

Is there a reason I can't just turn over the crank by hand? I was doing it earlier this evening... There was some resistance of course but I was still able to do it no prob.

You wont be able to do a full compression test with just the turn of a wrench. At the very least a high powered drill!

 

[turbodieseldyke]

Any drill or impact wrench capable of turning the engine hard & fast enough to do a compression test, will zip the crank pulley bolt out.

[edit - only if you turn it backwards]

 

[vwishndaetr]

You wont be able to do a full compression test with just the turn of a wrench. At the very least a high powered drill!

Is it because it'll leak too quickly at max compression? Or something else?

Any drill or impact wrench capable of turning the engine hard & fast enough to do a compression test, will zip the crank pulley bolt out.

Ya I feel that way as well. I have a bunch of drivers I can use, but don't feel good about it. Also with the injection pump running dry, any risk of damage if I start cranking it like that for the compression test?

 

[Mongler98]

Have you ever turned over an engine by hand... yes the compression leaks out way to fast

A drill should not take off that bolt if you have all the plugs out and start it slow.... this is my fear hence why I copped up a trans for the bell housing I would not risk it though.

 

[vwishndaetr]

Have you ever turned over an engine by hand... yes the compression leaks out way to fast

A drill should not take off that bolt if you have all the plugs out and start it slow.... this is my fear hence why I copped up a trans for the bell housing I would not risk it though.

So let me ask it this way, aside from how to turn the crank, what is considered acceptable compression for a 1.9 AHU? If I start turning it over there will be some max value I hit when I'm cranking it, so what pressure is acceptable for adequate compression?

Also, another way I can do this is by doing a leak test no? If I get to the top of my compression stroke and fill the cylinder with air then the rate of pressure drop can also be attributed to having a good seal right?

I don't know what the criteria is for either in terms of max pressure or pressure loss per unit of time.

 

[Mongler98]

So let me ask it this way, aside from how to turn the crank, what is considered acceptable compression for a 1.9 AHU? If I start turning it over there will be some max value I hit when I'm cranking it, so what pressure is acceptable for adequate compression?

Also, another way I can do this is by doing a leak test no? If I get to the top of my compression stroke and fill the cylinder with air then the rate of pressure drop can also be attributed to having a good seal right?

I don't know what the criteria is for either in terms of max pressure or pressure loss per unit of time.

Its divination between them all that matters. Anytjing under 400 is probably bad news. 450ish is about right. Most high milage engines in good shape make about 420 to 440 a pop with 2 and 3 being the weakest numbers. You can have a running engine at 400 but anything less than 410 is a rebuild if the engine is out. Cold engine will produce less. Also make sure that its cranking on a full battery and a healthy starter. A few drops of oil down the hold or if able to rotate the crank with the starter for 3x 10 second intervals with plugs in or 30 to 40 seconds with them out in one go to get oil pressure up into the rings will produce the most accurate numbers.

 

[vwishndaetr]

Its divination between them all that matters. Anytjing under 400 is probably bad news. 450ish is about right. Most high milage engines in good shape make about 420 to 440 a pop with 2 and 3 being the weakest numbers. You can have a running engine at 400 but anything less than 410 is a rebuild if the engine is out. Cold engine will produce less. Also make sure that its cranking on a full battery and a healthy starter. A few drops of oil down the hold or if able to rotate the crank with the starter for 3x 10 second intervals with plugs in or 30 to 40 seconds with them out in one go to get oil pressure up into the rings will produce the most accurate numbers.

Thanks, that's helpful.

Would you happen to know what the threading is on the plugs? I'll try and pick up the compression tester on my way home from work. Might save me a trip if I can grab what I need on my way home.

 

[garciapiano]

Dear god, and I thought my car was a basket case. Looks like it was driven into a curb, hard.

My rule of thumb on compression is if it feels good, it is good. You should feel four specific compression pulses when turning the engine over, and it should be quite difficult. My 1Z was making good compression right up until the bearings wore out enough to have insufficient oil pressure...

Seems like it was owned by someone who was involved with the car, so that bodes well.

 

[Mongler98]

My rule of thumb on compression is if it feels good, it is good.

So you have the gift no one else on this earth has of knowing the difference of 350psi and 450 psi?
A tdi with under 300 would never start on it's own.
Your full of thumb is just as worthless as the origin of the rule of thumb..... need I quote "the boondock saints" movie for you?

 

[garciapiano]

So you have the gift no one else on this earth has of knowing the difference of 350psi and 450 psi?
A tdi with under 300 would never start on it's own.
Your full of thumb is just as worthless as the origin of the rule of thumb..... need I quote "the boondock saints" movie for you?

You're not wrong, but I also doubt most TDI engines would suffer from low compression. It's just not a super common issue. If anything, maybe do a leak-down test now that the engine is out of the car.

 

[Mongler98]

You're not wrong, but I also doubt most TDI engines would suffer from low compression. It's just not a super common issue. If anything, maybe do a leak-down test now that the engine is out of the car.

its the risk reward, do you spend the time and few bucks now to make sure you are not pulling an engine that you dont know its exact condition? other than that.. yea you are correct, not very common, but only in engines not pulled from a car... usually you see them in a car running. So if an engine is pulled, IMO, its worth checking. its not difficult....

 

[vwishndaetr]

You're not wrong, but I also doubt most TDI engines would suffer from low compression. It's just not a super common issue. If anything, maybe do a leak-down test now that the engine is out of the car.

Tell me more about the leak down test. In terms of numbers, what pressure am I applying and how long do I need to hold it/what is the acceptable drop in pressure?

its the risk reward, do you spend the time and few bucks now to make sure you are not pulling an engine that you dont know its exact condition? other than that.. yea you are correct, not very common, but only in engines not pulled from a car... usually you see them in a car running. So if an engine is pulled, IMO, its worth checking. its not difficult....

I will say though, the car ran fine before the engine got pulled, and when cranking the engine when it was out of the car everything felt good too. Even the turbo has minimal shaft play so I can only presume it was replaced at some point. The injector pump also has markings on the hardware to indicate they were torqued - certainly doesn't look like the hardware was marked 24 years ago. So once again, while there is some janky **** going on with the car, I do think there was a decent amount of maintenance that happened recently (more than likely with the owner before the one I bought the car from).

I'm only seeking out the compression test so if there is something going on, I can address it now. Otherwise the engine is going back into the car.

I think I'm just going to get a compression tester and call it a day. You said it yourself, it's mainly the difference between the cylinders that's important as long as the compression isn't dramatically low. Also, since the car was running and you guys mention low compression is highly unlikely, it's probably even less likely that it'll be low across all cylinders. So regardless of how I do my check, as long as the way I check it is the same for each cylinder and the compression is consistent then I should be good to go.

Unless someone else has a better plan, I feel pretty good about it.

 

[Rig]

Wow. I don't have anything useful to say. But that exhaust.... why ?!

Good luck. I mean, I'm sure it needs a ton of work but the thing I love about this car is how relatively simple it is once you understand all the parts. Keep us posted! About to do a compression test on mine.

Btw, anyone know a cheap and good tester for this car? I'd rather not spend $120 at harbor freight for the full set and all the adapters. Will only need one size and I'll probably only use it once.

 

[ToddA1]

Keep going with the pics.

I’d love to see the size of the drill that can spin the engine fast enough for a compression test. Most people rely on the battery and starter.

-Todd

 

[Lug_Nut]

... IMO that exhaust is actually awesome and not even one HP was lost...

Really? Look at the reduction in the effective cross sectional area.

Any drill or impact wrench capable of turning the engine hard & fast enough to do a compression test, will zip the crank pulley bolt out.

The crank bolt damper bolt is right hand threaded. It might tighten if it is used to spin the crank in the same direction it turns if running.
That said, the crank damper bolt is a TTY fastener. Mark it and the damper before trying to turn the engine to determine if the bolt moves at all, whether looser or tighter. Replace it if there is any movement. Since you will be doing the timing belt anyway, add this bolt to the parts to be replaced and crank away with the old one.

Btw, anyone know a cheap and good tester for this car? I'd rather not spend $120 at harbor freight for the full set and all the adapters. Will only need one size and I'll probably only use it once.

Can a "loan-a-tool" auto parts store provide one?
I tend to borrow from those as a once-and-done tool source, then to "Horror Fright" to buy one when I invariably I need that tool again, and finally a quality replacement when the cheap one fails.

 

[Mongler98]

Really? Look at the reduction in the effective cross sectional area.

This was a joke.... bit since you got serious... it actually would not decrease power.
Motor trend did this test and no matter how much you pinch a pipe or how many times you do it , it wont rob any HP..... even if it's close to being pinched shut

 

[ToddA1]

This was a joke.... bit since you got serious... it actually would not decrease power.

I can’t believe that. You’re inferring mandrel bent tubing is a hoax?

-Todd

 

[Mongler98]

I can’t believe that. You’re inferring mandrel bent tubing is a hoax?

-Todd

No. There are things called EGTs and this nasty velocity thing and manifold pressure.
Go watch the motor trend video on the myth of if you have to sing a manifold to go around something it robs HP. Well they ended up pinching 80 to 90% of all 8 header popes nearly shut... dyno still has withing 5% the same HP. And this was on a 500hp v8. A TDI pre turbo would never work the same but post turbo.... it makes nearly no difference in HP as long as you dont melt things l!

 

[Rig]

Ok, so I am looking at this gauge here: https://www.partsplaceinc.com/vw-di...974.html?utm_source=google&utm_medium=FreePLA

I'd rather not buy a whole kit with 20 adapters I'll never use. So is the correct adapter to fit the glow plug threads?

VW TDI Compression Tester Adapter - Free Tech Help

The VW TDI Compression Tester Adapter you need plus free tech help from true VW experts. Same day shipping. Order on-line or call today!

www.partsplaceinc.com

Only reason I ask is that they say stuff about injectors but the adapter looks like a glow plug... sooo

 

[turbodieseldyke]

The crank bolt damper bolt is right hand threaded. It might tighten if it is used to spin the crank in the same direction it turns if running.

The engine runs counter-clockwise. That would loosen the bolt. I never imagined the engine could/should turn backwards to check compression.

[edit - not counter-clockwise]

 

[garciapiano]

The engine runs counter-clockwise. That would loosen the bolt. I never imagined the engine could/should turn backwards to check compression.

Not sure if we are talking about the same engine… this engine definitely turns clockwise.

 

[turbodieseldyke]

Not sure if we are talking about the same engine… this engine definitely turns clockwise.

I must have a brain tumor.