RyanH.

Since I'm unsure of recent service history on a few items, I've been tackling all the maintenance items on my 150K 1990 C4. Next week I'm planning on doing the below and wanted to see what else I should do while I'm down there:

• Valve adjustment
• Spark plug replacement
• Replace valve gaskets
• Timing chain cover gaskets
• Replace fuel filter (should I replace one or more of the fuel lines too?)
• Remove intake manifold and clean oil/gunk (any parts that should be expected to break/need replacement)?
• Remove cruise control if accessible
• Remove fuse box if time permits
• Cat bypass tube with new O2 sensor

Anything else? Timing chain covers is going to require lowering the engine. Will it be lowered enough to also remove the A/C bracket so I can cut it down? Anything in the above that I should anticipate breaking and should have spares on hand?

There's a part of me that just wants to drop the engine and tranny so I can also take care of a few other things including checking to see if the planetary gear has been welded BUT...I'm pretty sure the wife would kill me if she has to park outside for more than the holiday week in case things go on a little longer than anticipated...decisions...decisions.

titleistaddict87

Sounds like so much fun! I'm in a similar boat (129k mile 1990 C2 Targa) and can't wait to get to this stuff. Don't have answers to your questions but subscribed for the expert info.

The one thing I have done on your list is replace the fuel filter and wow what a difference. Old one was 7 years old and now the car idles smoother, doesn't stall in reverse, and just pulls stronger / smoother in all gears.

Spokes

I would probably add new spark plug and distributer cables, new distributer caps & rotors (if worn). I recently dropped my engine & tranny (c4) and welded the planetary gear while I was there. Unless the chain covers are leaking badly I would leave them until you drop the engine. It is not easy to access the covers even with the engine out (I know others have done it with the engine in). Also removing the AC bracket requires the bottom pulley removal.

cobalt

If this is the first of this type of work in 150k miles i would consider a full drop. Then you can access Power steering belt and gaskets. These gaskets turn to plastic and leak. Also if you are removing the intake replace the seals around the oil sending temp housing and everything up top they have a tendency to leak as well. It is an easy cheap fix and assurance. I would consider the timing chain cover gaskets now with new rubber grommets they shrink after all these years. You will need to remove everything at the back end to access the right hand side.

I would be careful with the fuel lines. Honestly if you move them odds are they are old and brittle and will eventually leak and need replacing. Now is a good time. Also replace the injector seals the three seals to the oil bridges to either cam tower. IMO don't use the red seals to the timing chain cover try to order the black later and 993 version the red ones flatten out too easily. Whatever else you find while you are at it. You might consider making spacers instead of cutting the a/c bracket. This way you can always return it to stock and save the expense of having to buy the bracket again. IMO always best to do it all at once and be done. Also check for slop of the upper rocker arm bushings they have a tendency to wear if they haven't been adjusted in a long time also blow out the oil squirters to the upper rockers while you are replacing the oil bridge seals. If these clog there is no oil sent towards the rockers to splash and feed the rocker arms.

RyanH.

Thanks for the thorough answers. Regarding the spark plug wires, is there a way to visually check whether they should be replaced? Also, it's 2x distributor caps and rotors, right?

@cobalt
Should I replace all the fuel lines Rob circled? https://rennlist.com/forums/964-foru...l#post10579187
When you say spacers for the A/C bracket, I hadn't come across that yet as an option. Is there a thread about that? I tried searching but couldn't find anything.

cobalt

You can check for any arcing while the engine is running in a dark location. Also look at the ends and wires to see if there is any cracking. It adds up I know but if they are original to the car I would consider it if they need it now or not. If the wires are good and you have a bad end you might get away with changing just the end out but odds are the others will go eventually if that is the case. Check the caps and rotors. You can try cleaning them with some light Emory cloth or a small file but if the carbon buildup has eaten into the copper contacts to deeply I would change them. This can waken up a tired engine if they are bad. Also while you are at it check your distributor belt. You might also consider taking the time to check the contacts on your injectors. I have seen these corrode and not fire properly. A small file can usually clean these as well.

If you can do a leak down on the engine before you start it might not be a bad idea. You might be able to rent a tester at a local auto parts store. As far as the fuel lines. I would inspect them closely. If they are still pliable you might be OK it all depends how the car was stored over the years. Just don't bend them too aggressively. If there are any cracks or are stiff I wouldn't take the chance. The biggest issues are usually around the crimped ends. They could also break down internally which will just clog the system. You might be able to have a hose shop rebuild them for you if you have one locally. The lines can add up.

If you can do the work the labor is a significant part of the cost and a simple drop and sealing of the engine with all the bits plus new wires, caps, belts etc can set you back well above $12k from an independent shop. If you do everything at one time it might break the bank but you will appreciate the peace of mind knowing everything is good and you won't ever get stranded or need to drop the engine again for many years to come. So unless you have records stating what was done and when having a fresh starting point is always nice vs fixing a little at a time.


You would need to have a local shop make you some spacers or if you can buy some aluminum bar stock about 1" to 1.5" in dia cut 4 spacers equaling the width of the bracket and drill a hole in the center. It will save you some weight as well.
GL

elbeee964

+1. I've replaced two in 120k miles. It's amazing the mess that oozes past this big ol' green rubber ring seal (once they age and harden) and deposits Everywhere on top of the block. It's an easy DIY job once intake thingees are moved out of the way. There are a few threads on the task; one of them by "Garret", as I recall.

+1 First post-purchase going over I had by a shop revealed this (cam end seals) were leaking out (misting?) oil. Technician showed me the betraying symptom: little pinpoint spots of oil depositing on the outside of engine cover. And this was in 2006 for a '93 with 70k-ish miles. They replaced it and now, at 120k miles, the seals are still sealing well. This is an elbows-deep task that I saw at the time that and (given my 964 experience level at the time) I'm glad I left to others to accomplish.

1) Electrical rubberized bits are notorious for difficult to identify failings. There've been proponents in deeply past threads who've argued using misting water over engine bay lines to detect arcing of failed spark plug wires. Me? I did prophylactic replacement of my wire set in 2008 and haven't looked back.

2) Yes, the distributors/rotors/plugs are 2x the number seen on pre-964 911's. You'll need 2 distributors, 2 rotors, 12 plugs. A pre-tear-down photo of plug wiring going into the top of the distributors can be helpful. It's a PACKED arrangement, with little room for artistic license for alternative patterns. So, too, with the routing of spark plug lines. FWIW, taking a few overview photos as you're about to dig into an assembly could be helpful when later rebuilding.

cobalt

I just refreshed this late 91 engine for a friend. Amazing what you find once you are in there. At 110k miles his seals were shot. I tried to get him to replace his wires, fuel lines and valve covers but he didn't want to spend up for it so I have no doubt we will be doing it in a few years. The mess up top from the leaking seals was significant. I ended up refinishing the valve covers but they are in rough shape.



These were the power steering pump and what most of his seals came out like. Dry, flat and just broke apart.



These were the grommets that keep the timing chain covers held in place. The old on the right shrunk over time by nearly .100" they keep pressure on the actual seal which was leaking badly.


Was also a good time to refinish his engine tins

964tit

I'm going through something similar at the moment. If the engine does come out, it's seals and gaskets ahoy! Including things like the crank-case breather gasket, oil pressure sender gasket, IMS end-cap gasket and so on.

Also, consider putting the RSR rocker shaft seals on the rocker shafts. It's a bit of a dick around, but might prevent some oil leaks around the valve covers.

https://rennlist.com/forums/964-foru...ker-shaft.html

"peek-a-boo..."

RyanH.

Man, it's a slippery slope. What starts off as a simple valve adjustment can quickly turn into a full rebuild.

My preference would be to pull the engine and work on it over the next month but that means the engine would have to take up my wife's parking spot and she won't go for that (for more than a long weekend). So, current game plan is to address what I can with the engine in over Thanksgiving, including a leak down test (I bought a tester awhile ago) and then decide what I want to do over Christmas holiday. I can probably get away with having her park outside for that week without too much groaning but I'll need everything prepped ahead of time to make sure it doesn't bleed over into weeks (or longer). My goal was to do the rebuild in the summer since my presumption is that builders are less busy around that time since most want to drive their cars during the summer.

Speaking of rebuilds, has anyone gone ahead and purchased low mileage parts, sent them off to get checked (and machined if necessary) and then gone straight into the rebuild without having to wait many weeks to complete? I guess the one issue is that the case would still need to be machined, correct? Or is that not always necessary?

RyanH.

Also, here's the parts list if anyone is curious (most of this is purchased through 5150Motorsports which is a lot cheaper than everywhere else and they ship quickly):

• 34x Engine Valve Cover Washer 999-025-193-30
• Timing Chain Cover Gasket Set (964-105-181-01-98)
• Bosch Oxygen Sensor for Cat Bypass (965-606-126-01)
• 12x Spark Plug - Bosch FR-5-DTC ( 999-170-183-90)
• Mahle Fuel Filter (928-110-253-06)
• 2x Bosch Distributor Caps (930-602-919-01)
• 2x Bosch Ignition Rotors ( 930-602-902-02)
• Green O-Ring (999-707-314-40)
• Power Steering Belt (964-147-187-03)
• Valve Cover Gasket Set (964-105-902-00)
• Power Steering Hose (964-347-445-03)
• Power Steering Seal Kit
• Intake Manifold Rubber Hose & Seal Kit
  • Two - 96411068503 - Genuine Porsche Rubber Intake Sleeve - Air Distributor to Throttle Valve Housing Upper Inlet
  • Two - 96411068603 - Genuine Porsche Rubber Intake Sleeve - Air Distributor to Intake Valve Housing Lower Inlet
  • Six - 99311071301 - Victor Reinz Intake Manifold Gasket (Rubber Seal Ring)
  • Six - 96411068703 - O.E.M. Rubber Intake Sleeve - Air Distributor to Intake Manifold

964tit

I’ve never tried valve adjust on the upper valve train while the engine is in. You might need to be a contortionist?

cobalt

If you have never done this before and plan to do it under time constraints in the car I would consider taking a step back. IMO you might find you will miss your Turkey dinner assuming you take the full week. I would consider changing the plugs, caps and rotor and also the fuel filter. You can try adjusting the valves with it in the car and only after you remove all the engine tins but you might find it more challenging to get right than you can imagine. It is a PITA to get right with the engine out of the car and that is assuming you have no issues along the way. IMO loose is better than tight and you will never be precise doing it in the car. Exhaust bolts might be a bit of a challenge if they haven't been removed in a long time. I would plan to replace those as well. IMO do your assessment and plan a drop over the Holidays. Trying to take short cuts on this or limiting yourself to a set time can prove frustrating. AFAIK you will need 40 washers and I would replace the nuts for the covers as well. The green seals are Viton. If you attempt the timing chain gaskets the rubber grommets are a must. Left side is easy. Make sure you have a secure way to support the engine to do this work. I personally have never needed the rocker shaft seals if you do it right they don't leak also you don't need to remove anything unless you have worn rocker bushings. If that is the case you will be stuck and have to remove them and have them repaired or replaced.

Trying to attack the power steering with the engine in the car isn't going to be fun. I would consider holding off until you drop the engine. Much easier to access with the engine dropped. Also consider the valve chain tensioner gaskets. These are easier and usually leak.

Doing a full rebuild is far more involved and unless you have a machinist to inspect and verify what condition the case is in I wouldn't consider it until you do. most of these engines I find with 100k miles don't need anything more than a reseal and you can live with the slight weeping of the chain housings to case seals until you need to.

Result of leaking power steering to cam shaft seal leak.

RyanH.

I took Cobalt's advice and decided to wait until the end of the year to tackle the valve adjustment and instead take care of a few of the other things I've been meaning to get to. As I was stripping down the Intake Manifold I found a bubble in the fuel line. Is this the correct replacement part for the part where the screw driver is pointing to:

https://www.pelicanparts.com/More_In...AaAnylEALw_wcB




Guess it was a good thing I decided to tackle the intake manifold cleaning today...yeesh.

wallra

yes that's the right line