Intake Manifold leak or ??

[doity]

I had a shop do some electrical work on my car a good year and a half ago.  They are mainly a auto electric shop but also do general car mechanics.  They initially did some work and also did a workup of all it would take my numerous electrical gremlins.  The car was getting oil into the coolant reservoir and they replaced the intake manifold gasket.

 

After doing all of the work, mechanical and electrical, I put the car into storage because it was still running like crap and it was not reliable.  I took it out of storage a few months back and have slowly been getting it running somewhat reliably, except for the idle which is weak at startup and will cause the car to stall until fully warmed up and on the road.  I took it to my mechanic for some fluid changes and a tune-up but he said that the plugs and wires were good but recommended a fuel system cleaning where he hooked it up to some machine which sends a chemical to clear out the Iines, injectors, etc.  

 

it ran noticeably better but he said that I had a leak in the intake manifold and he demonstrated this by spraying carb cleaner around the intake manifold gasket and the idle cleared up, at least until the liquid dissipated.  I called the other shop back and waited 2 weeks for an appointment.  I told the mechanic that since I had only put 1,000 miles on the car since the work I hoped that it would be covered under warranty.

 

They have it since last week and I finally called them and he said that he thinks that there are other vacuum leaks that he wants to investigate/fix first.  He mentioned something called a ‘Vacuum Tree’ which is close to the intake manifold.  I told him what my other mechanic said and he got a bit defensive.  I don’t mind paying for real problems that the car might have but money is tight now and I need the car due to an emergency.  Does the Vacuum Tree explanation sound plausible or should I just demand that they either fix their work or pay up? He did mention giving me a couple hundred back and I could have the work done elsewhere, or not at all I guess.

 

thanks for any help!

[2seater]

There are several vacuum lines connected to a plastic box on top of the intake manifold just behind the throttle body, perhaps what they are referring to. It does get brittle with age and heat and is easy to crack or break a hose nipple if not cautious. I didn't see a year in your post but 88-90 have the PCV system buried on the right rear of the intake plenum and can also be a leaker, but less common.

[doity]

Thanks for the reply 2seater.  How hard would it be for them though to isolate exactly where the leak(s) are coming from?  They have had it close to a week now and it took me calling to even get an update.  The mechanic there that I have been dealing with made it seem like he wanted to rule that out before delving in to the intake manifold but to me that seems like just they are avoiding any responsibility or at the least just trying to apply guesswork.

[Ronnie]

2 hours ago, 2seater said:

There are several vacuum lines connected to a plastic box on top of the intake manifold just behind the throttle body, perhaps what they are referring to.

 

I think the item circled in red, (sometimes referred to as the spider), in the photo below is what 2seater is referring to. If you want to isolate most of the vacuum lines as the source of the vacuum leak you can remove the 4 lines on the vacuum ports of the spider and cap them off. As 2seater said, the plastic can be brittle and prone to breaking so be careful with them.  If the engine runs good with those lines capped then you can start looking at the vacuum lines for the source of the vacuum leak.  I don't think capping those vacuum lines will eliminate the PCV valve as being the problem. You will have to dig around on the other end of the intake to find it.

 

 

 

The lines in this photo a prone to rotting and leaking.

 

 

[doity]

I should had said initially that it is a 1988.  Ronnie I see your photos and that helps but are the 4 vacuum lines that you mention related to emissions?  Because the main symptom is a lean idle and stalling.  It does run fine after a good 20 minutes or so and I chalked that up to maybe the intake manifold gasket expanded a bit with the heat from engine and seals properly.  If there were bad hoses I don’t see how it would run better once warm......unless I am missing something?

 

I don’t mind paying for work that ‘needs’ to get done, but I just hate to throw money at an issue unless the mechanic is 100% certain.

[Ronnie]

I don't know if those vacuum lines are considered part of the emission system or not. I think one of them goes to the purge canister that traps fumes from the gas tank so it might be considered part of the emissions system.  I know that one of them goes to the vacuum modulator on the transmission, and one of them supplies vacuum to operate the cruise control and the climate control.

 

26 minutes ago, doity said:

I don’t mind paying for work that ‘needs’ to get done, but I just hate to throw money at an issue unless the mechanic is 100% certain.

 

I can understand that.  I think your mechanic is correct in trying to rule out all other possibilities before changing the intake gasket for the second time. I am surprised that it has taken a mechanic a week to rule out a vacuum line as being the problem.  I don't think anyone here will be able to tell you with any certainty if your mechanic is doing the right thing.  If you have any doubts about your mechanic I suggest you find another one.

[2seater]

Ronnie's photos are always so helpful. That one closest to the camera is the vacuum purge line from the canister and since it is outside the throttle, there is no vacuum there. The next one back with the elbow is the fuel pressure regulator and the last one on the left (front) side is the vacuum modulator. Be careful with that one. If memory serves, the steel line actually inserts into the plastic nipple with a rubber sleeve over it. The small one on the right (rear) side is for all the vacuum to run the HVAC system and cruise control, while the large line should be capped off , and be sure it isn't falling apart. Common part on the LN3 engines in the salvage yard. Others may look similar but are slightly different and may not seal to the manifold. I make my own with a small solid aluminum or nylatron blocks and brass serrated nipples.

 

It is odd it is taking this long to track down a vacuum issue. The simplest way to eliminate the spider as an issue is to pull the bolt and lift it just enough to slide a piece of duct tape underneath, sticky side down. As for the time needed to get it to run properly, that is the opposite of what I have seen in the past. Cold engine start it runs in open loop, elevated rpm and richer than normal so it sometimes covers up vacuum leaks or other small items which are exposed when the sensors come online and take over.

[bikemikey]

When I bought my 89 Reatta it had some vacuum leaks. My car had 120,000 miles on it at that time. The main culprit ended up being the PVC valve grommet. They become hard and brittle with time and mileage and prone to leaking. I would have your mechanic spray some fluid just around the PVC grommet area to test for a leak before changing the intake gasket. Like 2seater said, they are buried and hard to replace, probably often ignored. When I went to replace mine it just crumbled into pieces.  

[doity]

Talked to the mechanic today and he said that he did replace the PCV hose but that was not the source of the vacuum leak. He is certain that the leak is coming from the ‘Tree’ as he calls it and GM no longer stocks the seal or gasket.  He said that they are working on fabricating a part so I should know in a day or two if that is the cause.  

 

Thanks for all all the great help guys.  This board is like a godsend sometimes and it is good to know that there are other people like me  who are gluttons for punishment by owning a Reatta. 🙂

Edited August 21, 2019 by doity (see edit history)

[Blue90]

4 hours ago, doity said:

 He said that they are working on fabricating a part so I should know in a day or two if that is the cause.  

 

You may want to check with one of the vendors here for a good used part; cheaper, I'm sure, than one being fabricated, which may not even be the problem.😉

 

4 hours ago, doity said:

Thanks for all the great help guys.  This board is like a godsend sometimes and it is good to know that there are other people like me  who are gluttons for punishment by owning a Reatta. 🙂

We try not to talk about our addiction in public!😎

[GALINDO]

https://www.wholesalegmpartsonline.com/products/HARNESS-Cruise-Control-Vacuum-Engine-Vacuum-Pump-Vacuum-Power-Brake/2996782/24500714.html

The part thats circled in Ronnie picture is this one 

[2seater]

58 minutes ago, GALINDO said:

https://www.wholesalegmpartsonline.com/products/HARNESS-Cruise-Control-Vacuum-Engine-Vacuum-Pump-Vacuum-Power-Brake/2996782/24500714.html

The part thats circled in Ronnie picture is this one 

Did you notice it said no longer available?

[padgett]

Typical. Not hard to just make one. Since brakes are electrical and not vacuum, nothing needs much. Are a number of ways to find leaks, a can of wd-40 is handy. Vacuum leak can really make cold starting chancy