# 1989 Cabby oil pressure gauge and light trouble....



## helicfii (Apr 15, 2009)

Hello forum- I am new here (just bought a used Cabby with 72k miles). No doubt, I will be around here for quite some time to come... 
I have spent 2 days reading through posts regarding oil pressure / gauge/ light problems, and have yet to see anyone really address these problems. Here is what is going on with my engine (I bought it like this- so I have no history of it behaving any differently than it does right now):
I AM RUNNING 20/50 WT OIL. No strange engine noises.
When the engine is cold, the oil press gauge displays excellent oil press (4-5.5 bar at cruise- 2300 rpm). As the oil temp slowly climbs to about 100 deg C, the press gradually drops until it settles in around 2 bar while cruising at about 2300- 2400 rpm. 
With the engine hot, when I let it idle (engine idle speed is not low), I get around 0.5 bar indicated on the oil press gauge, and the low press warning light will occasionally illuminate (at idle only). A slight increase in revs makes the light go out. 
It is my understanding that the light and the gauge are on separate circuits with separate sensors. I see no reason to go out and buy a mechanical oil press gauge to verify oil press, since both systems are giving me the same indication (low press while hot at idle). 
I plan to buy a super high volume oil pump and install it. While I have the pan off I am going to inspect the crank bearings as well.
I have read in this forum (and other forums) that when you have oil pressure indicated this low, that the motor is probably shot. Has this really been people's experience? This car has not been raced or abused as far as I can tell (an old man owned it). 72k miles seems a little bit low to be looking at crank bearing wear.
If I find no severe crank bearing wear, is it likely that the new pump will increase my idling oil pressure when hot? Is it possible that my gauge reads low and the warning light comes on when the engine is hot because BOTH of those circuits aren't working properly when the engine is hot (but they work fine when it is cold?- hard to believe that is true...!).
I guess what I am asking is: Has anyone installed a high volume pump that has had this problem, and found it to cure the problem? 
Any and all replies are appreciated. Thank you. 

http://****************.com/smile/emthup.gif


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## kamzcab86 (Feb 14, 2002)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (helicfii)*

The gauges in Cabriolets are not 100% accurate. They merely give you an indication of what's going on under the hood. When the oil pressure warning system starts acting up, the first thing you should do is test the gauge senders. If they check out, the next thing you should do is test the oil pressure with a mechanical pressure gauge.

_Quote, originally posted by *helicfii* »_
It is my understanding that the light and the gauge are on separate circuits with separate sensors. I see no reason to go out and buy a mechanical oil press gauge to verify oil press, since both systems are giving me the same indication (low press while hot at idle). 

Incorrect, to a degree. The low pressure at idle and warning light are wired to the same oil pressure switch: the one on the side of the cylinder head. Test the low pressure switch on the cylinder head by removing the yellow wire; if the warning light stops flashing, the switch is faulty and should be replaced. The 0.3 bar switch is normally closed until it senses low oil pressure, at which time the switch opens, breaking the path to ground.
There is also a high pressure switch (on the filter flange) that will warn when oil pressure drops to 1.8 bar or below at higher rpm's, but your car is not having that issue.
As for the oil pump, you can certainly install the higher volume pump, but I'd go the cheaper and less annoying route first by verifying that the pressure is good and that the gauge sender/pressure switch isn't faulty.










_Modified by kamzcab86 at 9:40 PM 4-16-2009_


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## helicfii (Apr 15, 2009)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (kamzcab86)*

Thank you for your response. 
Are you saying that there is a possibility that the oil press sending unit on the cylinder head is sending incorrect voltage to the gauge & warning light only when the engine is hot? I would think that a pressure sending unit would not be affected by normal changes in temperature- that it would either work or malfunction regardless of temp (but what do I know of the inner workings of these units? Nothing.). Is it possible for the unit to fail or give erroneous info only when it heats up? 
Thanks again


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## twinair (May 12, 2008)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (helicfii)*

While 72,000 miles is low it doesn't mean severe engine wear hasn't occured. I recently bought a 90 Cabby with 63,000 miles. The engine is sitting in my basement on a stand because of severe engine wear. By sever I mean number one rod bearing in a million pieces destroying the oil pump, crank shaft, and connecting rod. I'm not saying something this bad is happening to you (you would know it right away if it were) but bearing wear beyond limits is possible.


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## WaterWheels (Aug 14, 2005)

You are correct in that the two, pressure and warning light, use two different wiring curcuits. I think the confussion is in the pressure switches used to run the warning lights. What you are talking about is a seperate oil pressure gauge which does have it's own wiring. So yes, it would be rather strange for both to indicate low pressure it it really were not true.
What was stated above about the milage not really being an indicator of the engines condition is true. Buy the cheap pressure gauge and install and test the oil pressure so you know for a fact the pressure. Remember, you are thinking that a new oil pump might fix things, if the engine has low milage then the oil pump should be fine also. Can't say if the bearings are bad, sounds that way, or if the pump is bad, does not happen as often as they are replaced. But I can say something is wrong and the only real way to find out is to get a base-line pressure which is correct before going deeper.


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## helicfii (Apr 15, 2009)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (WaterWheels)*

It's funny you know- a lot of people come onto tech forums hoping to hear what they want to hear (I think I am guilty of this). 
What I hate is buying tools that I will only use once, but buying a mechanical gauge is the only way to verify what is going on. Thanks for all your replies. 
I will conduct the switch test outlined above, and do a mechanical gauge test of the oil pressure and post my results later this week.


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## twinair (May 12, 2008)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (helicfii)*

I too hate hearing the hard truth!! But I love buying tools


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## Fat Rabbit (Nov 18, 2001)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (helicfii)*

Maybe you could rent an oil pressure gauge or sometimes car parts places will rent tools or simply let you use tools for free. 
The oil pressure sender unit on Cabbies is $50-70 new so I'd check the pressure before spending that much money on a part. I presume that your car has the sender/switch attached at the end of the cylinder head. It's dual function for the light and gauge. Other models just had a couple of $6.00 switches. The PN is 035 919 561A if you have to order one. 
The oil pump is easy to change out -- just remove the oil pan and it's right there. Get one for a 2.0 -- they pump more volume. Use a 10mm socket on a 1/4 inch drive extension to reach the bolts between the oil pan and the transmission flange -- they are way up in the crack between there. 
It's been around 20 years since I used to hang around Kailua-Kona. People in general were very helpful there. The Ace Hardware store was great to me -- they let me use their shop and tools to fix my bike after an Ironman race official cranked my aero handlebars at bike check-in. Couldn't have done it without them. FR


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## helicfii (Apr 15, 2009)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (Fat Rabbit)*

It's beautiful here, but these days there is a serious lack of parts sources- every part or tool I need has to come in the mail! I do have the dual sending unit. Thanks for the part #


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## GoLfUnV (Oct 30, 2003)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (helicfii)*

I am having exact same problem, let me knwo what you conclude.


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## EtienneAignerCab (Apr 22, 2009)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (GoLfUnV)*

bump i am having the exact same problems too


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## dubluv3 16v (Aug 1, 2004)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (EtienneAignerCab)*

i have the same prob. i just installed a center console with the three gauges. i wired everything up and it does the same thing. so i have another press sensor/oil light sensor and it puts out the same reading the light comes one when hot. i pulled the pan and checked the pump no sludge no play everything is clean. reinstalled it same thing so i put the original little sensor in an now the dash light stays off but the press gauge still reads .5 at idle


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## helicfii (Apr 15, 2009)

*Re: 1989 Cabby oil pressure gauge and light trouble.... (dubluv3 16v)*

Hell, I changed my double sending unit and now my gauge reads 1/2 bar when the ignition is switched on and the engine is not running!!!! It also reads a higher oil pressure when the engine is cold at 2000- at least 1 bar higher. I wonder who calibrates these things- monkeys?
I will be removing my pan and pulling the bearing caps in about a week to check things out, and will install a high volume pump while I am in there. I'll get some pics.


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