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Overheating & EGR Delete


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I intentionally made a story out of this, because I personally like to read the stories of others. Furthermore, I find a little background story helpful when trying to help other find a solution to any issue!

If you dont want to read the background, skip on down past it 😃

 

Background:

I bought my '78 S30 on July 13th, 2021. It had roughly 66,000 miles on it and now has 67,651 miles on it. Prior to my ownership, the car sat for ~10 years. Before that, the story was not clear. 

On August 31st, 2021 I was driving from (Bellevue & I25, Colorado) to (Kipling & I70, Colorado) which is about a 40 minute drive, when it was roughly 93 degrees Fahrenheit out in heavy traffic. For the first time, my Z was overheating and just about to hit 250 degrees Fahrenheit on the thermometer roughly 35 minutes into the trip. I pulled over, expecting to see no coolant or some issue... except I saw nothing alarming. While it might be shocking to see the coolant boiling in the coolant reservoir, there were no visible issues.

I let the car cool down for about 45 minutes, and drove to my destination.  Started it back up again maybe 90 minutes later to drive home, which is about a 20min drive. The car started to build temperature about 15 minutes in, but not like it did when I first noticed the issue. This time it got closer to 200-225 degrees Fahrenheit, which was still a bit alarming.

I parked it and had wait until September 5th, 2021 (the weekend) to work on it and diagnose the issue.

My first thought was that the fluids needed flushed and changed. The previous owner told me that he drained the gas tank, changed the brake fluid and front brake pads before he started it. But I doubted that he had changed the coolant, and it looked a bit dark.

So being a greenhorn DIY mechanic, I bought some tools (which I am stoked to have now) and started to work on the car. I drain the radiator fluid, put the radiator flush in, start the car to cycle it (this time with the hood open...which we typically dont do when we are going for a ride), and the car sounds a bit louder.

I get out, with the car on, and try to find the source of this noise and I find a pipe that should be connected to the exhaust manifold that is rusted off. And I have no idea what this part is. A couple Google searches, and I discovered it is the EGR. I touch the device and it is clearly hanging by almost nothing. A couple solid speed bumps and it would have just fallen off. I wiggle the pipe, and it simply disconnects. The EGR is still mounted, but it is not truly functioning without the exhaust pipe. So now I am thinking, the issue was not the radiator. The issue was that exhaust was just pumping into the engine bay. And exhaust is kind of hot...

But now I cant start the car to flush the radiator cleaner out, because without the EGR there is no vacuum. My simple fix is to just use heat tape, and cover the EGR ports to start the car and cycle the Radiator Flush. This is not a solve I would use daily, and I understand is risky.

 

The Issue(s):

  1. The Engine is overheating
  2. Discovering that the EGR pipe is broken...broken parts are not good. But this could be the reason the engine is overheating.

 

Solution:

After a little research, an EGR delete seems to be the quickest solution.

I want to convert the L28 to carburetors soon which made it seem fiscally unsound to fix the EGR now. I cannot find Mikuni PHH 44 side drafts for under $4k. So I am waiting to buy some after I fix the floor pan rust.

The EGR delete seems pretty straight forward: Buy the EGR delete plate for the EGR port on the intake manifold, and plug the exhaust.

I cannot find solid research as to what to do with the opening on the bottom side of the intake manifold where the pipe from the exhaust manifold connects to the intake manifold. I am hopping that the same 22mm plug for the exhaust manifold fits the intake manifold as well. Here are the parts I bought to do this delete:

 

Then finish with the radiator flush.

 

Questions:

  1. Is there a viable solution to plugging the bottom of the intake manifold where the pipe connects the exhaust manifold to the intake manifold?
  2. Would the open exhaust be the most likely culprit behind the over heating the engine?
  3. Do you have any general tips on this EGR delete process?
  4. What Coolant do you prefer for your L28? Are there any products to specifically stay away from?

 

 

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I think that Captain Obvious has written some good stuff about the EGR system.  Can't remember the details, but I think that if you just seal the hole at the top of the intake manifold with a plate and a good gasket you will not have any vacuum leaks.  Sounds like you did that with tape already.  You don't need to seal the bottom because it is just a passage to the hole at the top.

I used a 16mm bolt inside the remaining piece of tube on the exhaust manifold, with some ceramic muffler sealant paste to seal the hole in the exhaust manifold.  Cut a groove in the bolt threads and it becomes a self-tapping screw thread.  Or, if there is a piece of pipe left in the exhaust manifold you could find a compression fitting and use that.  Or, simply, you could crimp it and fold it over with some vise-grips and it would probably seak just fine.  Ugly but effective.

Do you have your heater core intact or is it "bypassed"?  If you're not using the heater core you should block the ports, not bypass them.  Bypassing can cause overheating.

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I will throw my 2 cents in here too.

If you are looking a spending $4k or so on Mikunis, I would go ahead and get individual throttle body EFI for that or less.

It will make the same or better power, be easier to get tuned, idle properly when cold, etc

Edited by Patcon
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48 minutes ago, Zed Head said:

I think that Captain Obvious has written some good stuff about the EGR system.  Can't remember the details, but I think that if you just seal the hole at the top of the intake manifold with a plate and a good gasket you will not have any vacuum leaks.  Sounds like you did that with tape already.  You don't need to seal the bottom because it is just a passage to the hole at the top.

I used a 16mm bolt inside the remaining piece of tube on the exhaust manifold, with some ceramic muffler sealant paste to seal the hole in the exhaust manifold.  Cut a groove in the bolt threads and it becomes a self-tapping screw thread.  Or, if there is a piece of pipe left in the exhaust manifold you could find a compression fitting and use that.  Or, simply, you could crimp it and fold it over with some vise-grips and it would probably seak just fine.  Ugly but effective.

Do you have your heater core intact or is it "bypassed"?  If you're not using the heater core you should block the ports, not bypass them.  Bypassing can cause overheating.

 

I did do a search, and a Google Search of "EGR classiczcars.com" but couldn't find anything for it. I am not saying it does not exist, but am saying that I could not find one. I am sure it is helpful.

I have not checked the heater core at all, but have not been running heat at all. I know that the heater core serves as other purposes too though. But, now that you mention it there could be an issue with it that I have not considered. The cabin of the S30 is incredibly hot, and being new to owning a Z...I was not sure if that is normal or not. 

 

On the under-side of the Intake Manifold where the EGR is though, you are essentially saying that I do not need to worry about it. That the opening only functions if gases are being pumped into it, and that leaving it open will propose no major risk?  

 

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37 minutes ago, Patcon said:

I will throw my 2 cents in here too.

If you are looking a spending $4k or so on Mikunis, I would go ahead and get individual throttle body EFI for that or less.

It will make the same or better power, be easier to get tuned, idle properly when cold, etc

 

Would that mean abandoning the Mikuni path, and just going full fuel injection?

I feel like the Bosch FI system was already acting as an EFI.

 

Or are you suggesting to apply EFI to Carb's? I am just open to the fact that I am new to this sort of modification and have some learning to do!😃

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7 minutes ago, SupremeCling said:

 

Would that mean abandoning the Mikuni path, and just going full fuel injection?

I feel like the Bosch FI system was already acting as an EFI.

 

Or are you suggesting to apply EFI to Carb's? I am just open to the fact that I am new to this sort of modification and have some learning to do!😃

The factory system is very primitive. A modern efi system with closed loop fueling is miles ahead of the original system. Yes, a complete new system. Very similar to triple mikunis but triple throttle bodies instead. Look up Jenvey's

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Yes, you do not need to plug the bottom hole where the tube was. Or the other side either actually, unless you were leaving a unbroken tube attached to the exhaust. It’s just a hole through to the other side which goes to one side of the valve. The rectangle hole in the picture below is what needs to be plugged. The plates designed to cover both holes on top would work best because of how the holes and the mounting points are set up.

Here’s a pic from the top with the valve, riser, and studs removed. They were really frozen together and a pita to get off. The pipe is still connected to the bottom side.

e63b48ab9db49bffefc53615b02fa83f.jpg

Just the valve removed and plugged with carbon

1bb5950524aabe54f8bec08a5c7e63e9.jpg


Sent from my iPhone using Tapatalk

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Was going to add this graphic to my other post.  Shows the path of the exhaust gases, up through the round hole and right over and down in to the rectangular hole.

image.png

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2 hours ago, siteunseen said:

Where's my .02$ in a good thread of @Reptoid Overlords.

Captains EGR theory is in post #3.

 

Yes this was most helpful. Save yourself the trouble and don't read past post #8.  I used copper sealer on a Victor Reinz intake/exhaust manifold gasket and wrote a 1200 word dissertation about it haha.  My friend and I were making our own jalapeno vodka in those days.

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On 9/10/2021 at 4:58 PM, mailnome said:

Yes, you do not need to plug the bottom hole where the tube was. Or the other side either actually, unless you were leaving a unbroken tube attached to the exhaust. It’s just a hole through to the other side which goes to one side of the valve. The rectangle hole in the picture below is what needs to be plugged. The plates designed to cover both holes on top would work best because of how the holes and the mounting points are set up.

Here’s a pic from the top with the valve, riser, and studs removed. They were really frozen together and a pita to get off. The pipe is still connected to the bottom side.

e63b48ab9db49bffefc53615b02fa83f.jpg

Just the valve removed and plugged with carbon

1bb5950524aabe54f8bec08a5c7e63e9.jpg


Sent from my iPhone using Tapatalk

Awesome detail!

I guess it just feels odd to have a port of any type open! 

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On 9/10/2021 at 3:17 PM, Reptoid Overlords said:

Dayum

 

Those Jenvey's look really nice. And way cheaper than Mikuni

 

Any experience with them? 

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On 9/10/2021 at 2:46 PM, Patcon said:

The factory system is very primitive. A modern efi system with closed loop fueling is miles ahead of the original system. Yes, a complete new system. Very similar to triple mikunis but triple throttle bodies instead. Look up Jenvey's

I really might go that direction.

 

It would be hard to abandon my vision for the car. Maybe ill just come back to it in the future

 

That is one of the greatest things about these S30s. You can continue to work on them and change them

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