1976 280Z Replacement ECU Issues

[Mark Maras]

 Snake oil for valve trains. I've tried a few in the past and been disappointed with the results but a mild cam seal leak and a severe rack and pinion leak on our 97 Outback (spare car) made me dig deeper. After watching many snake oil reviews I decided to try AT 205. This stuff is amazing. Project Farm confirmed this on YouTube. I added the recommended amount to the power steering and engine oil. Although the car gets driven less than a thousand miles a year, it's been almost 2 years and I have not had to top up either reservoir. I haven't tried it on old rubber grommets and bushings but it may revive those too. The only negative reviews I found were from some Toyota owners stating that it removed the paint in the oil pans causing a blockage in the oil pick-up screen

[Dave WM]

The valve seals are not hard to replace if you have the right tool to compress the valve spring with the head in place. I would just do that, and at least it will no longer be part of the discussion. You will know right away when you get to them. The whole job will take less that 1 hour. 

[Zed Head]

The topic has come up several times over the years.  Put the words below in to Google search and a bunch will come up.  

site:classiczcars.com valve seal replacement

[siteunseen]

I've had good luck with:

Valve seal replacement classiczcars.com 

6 of 1, half dozen of the other.

 

 

[DD76]

Thank you all for your suggestions and advice. Though the job looks to be nerve wracking, until at least the first cylinder is done there are enough suggested write ups and videos to give good direction, particularly as it doesn't need to be on the road the next morning.  The small investment in seals and a spring compressing tool looks to be a great way to either solve the problem or eliminate one of the two most likely sources. Thanks again for the help. Great site.

[Dave WM]

just remember to make sure you stuff rags around the timing chain to prevent anything getting dropped down the hole. That would ruin your day....

give the valves a light tap with a plastic mallet after getting the keepers back in, just to make sure all is seated. A small magnet on a collapsible stick helps a lot when getting the keepers out.

Lastly the biggest issue I had was keeping the valves from compressing when using the spring compressor. I did not have much luck with compressed air holding them closed, IIRC I used some nylon rope, or maybe it was some plastic tubing, I don't recall, maybe both were tried. again a slight rap with the plastic mallet before applying the spring compressor may help to "break" the hold the keepers have before applying the compressor. 

I think I may have had the piston a couple degrees before TDC, then after getting the nylon rope in good and tight, use a 27mm socket to turn the crank just enough to really jam the piston to TDC, compressing the rope enough to keep the valve from decending. 

It sounds complicated but its not really hard when you get into it. 

 

 

 

[DD76]

Thank you Dave WM. I was wondering if the compressed air or rope plan was best. The extra hand cam turn to compress the rope is a great tip. Thanks too for the reminder on rags. That seems to be at the top of everyone's list. I do appreciate the help.

 

[Dave WM]

You could try the air, a lot easier, I would set the compressor up as high as you can get it. IIRC mine peaked out at about 120psi, pop the valves with the plastic mallet, you will hear them pop air under pressure, help to seat them, then give it a go. If not the rope trick works for sure, just more time consuming. I don't "think" its possible to drop a valve completely as long as the piston is at TDC (if you got foolish and had one at BTC, yikes) The reason I am saying this is the crank is going to want to turn under the pressure if you get just a hair off TDC. The more I think about it, the rope is fool proof...

If you have ever done a leak down test you will know what I mean. I dont think the piston would travel far enough to be able to lose a valve since the pressure goes away quickly as the crank turns. IIRC it only moves about 10 degrees off TDC.

 

Edited July 12 by Dave WM

[Dave WM]

maybe some one else has had luck with the compressed air method and can chime in. 

[Captain Obvious]

I used the rope stuffed in through the spark plug hole method. I didn't trust that my tired old rings were up to the task of using compressed air. I wanted something of positive volume in there.

Besides... I work slow. And the rope doesn't care. 

[Captain Obvious]

On 7/9/2024 at 9:26 PM, DD76 said:

I lost half a quart of oil in today's 50 miles, 

Are you really sure you lost that much oil? That's an awful lot!! Especially under normal driving conditions. Typically intake valve seal leakage is worst when coasting and the intake manifold vacuum peaks. But under normal driving conditions, that doesn't happen all the time, just sporadically.

I'm going to throw out a scenario.... You checked your oil before you started your motor and went on your drive. The level looked good.

However, unbeknownst to you, the night before, your anti-drainback valve on your oil filter leaked and some of the oil typically held in your filter drained back into the crankcase.

Then you went on your 50 mile drive and checked your oil shortly upon returning. At that time, you found you were about a half quart down.

I would propose that it may not have burned away, but maybe just shifted locations?

I've seen this scenario occur and just trying to get to the root issue before you go stuffing rope everywhere.  

[DD76]

Thank you for the thoughts Captain Obvious. I do think it's burning the oil. I did not check the reading on the dipstick before I did my first 25 mile ride but the last time I had checked, at most 10 or 15 miles earlier, it was about full.  When I checked after that run it was noticeably down into the crosshatched area. The next morning before the 50 mile run, I added no oil and rechecked the dipstick. It was sitting about 65 per cent to the upper end of the crosshatch. I actually had a good reference point using the number stamped on the back of the dipstick. After I got done the 50 mile ride I checked the oil and it was below any of the crosshatching, checked it the next morning, and again just now, and it's a little below the crosshatching. Assuming the crosshatch area represents one quart, I've actually lost the better part of a quart. There's no oil on the engine or the floor. I'd think if it was leaking into the clutch, I'd have clutch issues and no smoke. Granted a rear view mirror is not the best measurement tool but I am surprised at the amount lost because I really only saw very visible smoke starting from stop lights and some of the times I tried heavy acceleration or deceleration. I did ride it pretty hard, shifting at higher RPMs, etc. As noted in an earlier post, the smoke does not seem to occur while the engine is warming. The two mechanics I showed the plugs to both used the term blow by and felt the valve area was the place to start. I figure, no matter what, oil has to be coming from around the piston or through the valves so $100 and my time to do the seals (maybe live to regret) is a good first step. If it doesn't solve the problem, time for plan B. Dealing with valve jobs or rings is likely out of my league. Thanks again for the help. Is there something I could be overlooking?