Adding an Oil Pressure Gauge....

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Feb 9, 2006
Well, As soon as I can drop my sump and check the oil pickup mesh, I'll be much less worried about the longevity of my Saab. However, one thing that will always bug me is oil pressure. These cars also have weak oil pumps and are prone to premature wear. They also have only an iodiot light for oil pressure. So, how do I pick an aftermarket gauge. I just want something basic. I noticed there are choices of mechanical or electrical. Which is better? Where do you even hook up an oil pressure gauge to?
I like the mechanical gauge, partly because I found it easier to hook up. The electrical may be better as you don't have a tube of oil going into the passenger compartment. In either case, a sender or fitting screws into the block in the location of the existing sender for the dummy gauge/light. You may have to use a T to hook up the old and new sender if the old sender also feeds data to the computer (more likely on newer cars). My '95 F150 did not have that, at least that I am aware of. You can get a Sun brand gauge, either electric or mechanical, from Advance Auto or other popular parts stores for under 20 bucks and that will be good enough. Autometer costs at least 2X as much but is supposed to be a much higher quality gauge. I don't think it matters and I run a Sun in my motorhome. It has 5 psi increments. For mechanical, hook up the tube and wire the light. For electric, you have to hook up an electric wire from the sender to the gauge and power and then also hook up the light. I mounted in my pickup on the steering column with a carved block of wood painted black to match column and drilled holes in the cheap plastic column cover and used zip ties to hold the gauge on. In the motorhome I mounted it on top of the dash glued down in the supplied mounting bracket with Household Goop. Ran the tube down the defroster opening as the duct was out of alignment and let me sneak past it.
There are two options when using a mechanical gauge. You can use plastic tubing to carry the pressure to the gauge, or you can use copper tubing. My thought is that the copper would be more durable, and I have used this stuff when installing mechanical oil gauges in the past. I've had failures with the plastic tubing, but not with the copper. The cost difference isn't large. Most auto parts places will carry the copper stuff, but you have to ask for it.
The only thing that I don't like about most electrical gauges is that they're typically only 90° sweep from zero input to FSD (full scale deflection). That means all of your divisions within the index are less defined. You'll have 0-30-60 ..or 0-40-80 (anything like that) for reference points. There are some more expensive electrical gauges that offer the 270° sweep. I would get one of those. If you do go mechanical ..get the copper line kits ...WAIT! ...nix that ..get twp 1/8npt to 1/4" hose barbs and get stainless steel braided #4 hose. You can clamp it at either end ..or go to the trouble of getting the NPT:AN fittings and get real fancy. The stuff will take more insult then either copper or nylon.
Most gages come with plastic tubing. The one I put on my truck did. I found a place low on the dash where I could cut a hole and mount it and the amp gage. May have been 10 years ago or more. No problems with leaks. copper can vibrate, work harden, and crack. Be sure to leave a loop in it between the engine and body if you do use copper. My truck ain't got no puter. I still teed in the idiot light. it is easy to be distracted and not look at a gage that ''always'' read right. Did try to discipline my self last week to watch the gages when I was further from home than in years.
I think once we're dealing w/ lines, I'm okay, but getting the thing on the block is what bugs me....
I said nothing about that, thinking Tall Paul covered it. More detail? Oil pressure senders use what is called 1/8'' pipe thread. You will need a tee and a short nipple. NAPA may even have a brass tee with one male thread eliminating the nipple. Otherwise, go with black iron or cadmium plated, not galvanized, from the hardware store. Use Teflon tape on the threads or I prefer something like Loc-tite's Pipe-X. Watch your clearances. Unscrew the old pressure sender. Screw the nipple or tee into the block. Clearances may work better if the cross of the tee goes into the block. Screw the pressure sender into one port of the tee, and the fitting for the line into the other. Run the line to the gage. With copper leave a loop to flex between the engine and body. Keep plastic away from the exhaust manifold, etc. Keep either up away from road debris and out of the way of things you may be servicing. If you have to drill a hole in the firewall, like some issues, look at both sides carefully.
Argh, that's what I feared. The pressure sender is impossible to reach w/o removing the starter. I just paid someone to replace it FOR me b/c I didn't have the time. Maybe I can pay the same guy to install the gauge...
BTW what car and engine is it? Also I wonder if there is an alternate location for the gauge, a pre tapped port? The ideal setup is a mechanical gauge and an idiot light. If you suddenly lose pressure an idiot light is more valuable than the gauge because you will know instantly. Who looks at their gauge all the time?
If clearances next to the block are difficult or non existant, you could run a line out to where there is more room. As TallPaul said, maybe you can find another port. I think gages plus the computer check gages light is the best set up. As reliable as modern cars are, and even my 77 truck, your have to look at a gage a good many times before ever seeing a problem.
Hmm, I'm one of the lucky saab 9-5 owners on here! I know a few who have installed them, but figured I'd ask here first. The car has an idiot light, but evidently it doesn't come on until the pressure is REALLY low.
True BrianWC. I think most idiot lights don't come on until the pressure is around 7 or so psi. Summit Racing or JEGGs should have switches for idiot lights with higher psi. You want to check the hot summer idle pressure with the gauge though so you don't get one coming on at every stoplight. My F150 will drop to around 16 or 18 psi at hot idle. Really fancy would be to have two lights, yellow at a higher pressure and red and a lower pressure. If yellow comes on at the stoplight, no matter, but if yellow comes on during a full throttle run, look out!
I think first thing I am going to do is drop the sump. I've been putting it off but I'm gonna take off work if need be. I've GOT to see if I've got a clogged screen. Yes, your right Paul, the light on the 9-5 comes on between 6-7psi! Now I'm pamicking wondering if I'm gonna have to replace the oil pump!
Well, if you are dropping the pan and feel confortable with replacing the oil pump, it probably would be a good idea, if you have a lot of miles. The oil pump likely gets more wear since it runs unfiltered oil. I wish I had had the pump replaced in my F150 when they had the pan off because I think my relief valve spring is weak.
Hmmm, I don't know if you can replace the pump that way...I may have to call a saab mech but I thought it was practically an engine out deal. I DID speak with my trusty shadetree (the guy has seen saabs before and put my pressure switch on so that qualifies him...) and he said no problem on the gauge. He said he puts them on every vehicle he's ever owned. LOL, he said he wouldn't check tolerances for me b/c he makes more money off multiple small jobs than off larger ones that take longer.
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