Mk1 golf gti dx Oil pressure warning light flashing at low rpm?!

When I'm slowing down or idling my oil pressure warning light flashes red ?! Only when engine is warm… had the head completely rebuilt and everything too I'm worried please help

Well, the vis of the oil as in 5-30 synth, or 10w30 is too thin, under heat it thins more and the blinky light from hades usually occurs with those types of oils, when hot and at idle , add that to include a Generic, Fram, Bosch, or Store Branded Filters. (They have cost reduced them to ineffectiveness, and are missing the Drain Back Valve that tends to stabilize oil pressure at idle.

in my Cabriolet 92, 93 Digifant II I run 20W50 Castrol, and have used the following filters
Wix
NapaGold
PureolatorGold
Mann
Mahl
Genuine VW
Mobile1
STP

I have also had the blinky light from hades after I replaced the Pressure Can… I bought 2 and they both did the same.  So I spent the big bucks and bought one from a GOOD vendor ie: VW, and the issue went away.
I have also seen folks take the Can from the side of hte head and moved it to the Oil Filter On my Digi's there is a spare plugged oil port, that I have seen folks use to eliminate this.  

If you read all up on Dynamic Oil Pressure you will find that VW placed that thing on the Highest spot on the engine, and where the pressure is the least.

My two Pence.

Fit a new oil pressure sensor to see if it's just a faulty sensor.
There may be 2 sensors depending on what year car you have.

Low pressure sensor - blue or black at the side of the head.
High pressure sensor - white lives above the oil filter.


I use 10w40 semi synthetic in my car and never had a problem with it going to thin and oil light coming on in the many years I've had my car, perhaps the colder weather here in the U.K. compared to the USA where Briano1234 is based has something to do with it?

Mines a mk1 dx 1.8 cabriolet 1987, I did some trouble shooting today..
looked it over and the spade connector for it was off and loose to fit back on so I crimped a new one on, 
The problem persisted i.e. The light was still blinking at idle when hot, so I took the sensor out and put the old one bank into the head (low pressure sensor) 
The oil sensor that was giving me trouble was a new one..  I swapped the oil sensor back to the old one and the problem went away, but when I looked the car over again IT WAS DRIBBLING OIL lol there was a washer on the newer sensor that cut into my block and with the old one in oil poured out.. im stuck now on what to do 

Well, I personally would do the following
Get a Washer on the new old sender.
I just bought a new oil temp sender and the new one didn't have a washer and the old one's washer was a press fit.

Clean the Port area well with Brake Kleen and Plug the hole with arag to prevent dribble till your ready.
Use Black Ultra Permatex RTV at the Base of the new sender if you use a washer then both sides of the washer alone.
Remove the rag clean with cleaner again and then screw the thing in.  Let it set over night and you shoudl be fine.

You could also build up the chewed with JB-Weld, and sand it smooth, then screw in and use the RTV as well.

 

Go to a VW dealer and buy a new genuine sensor, they are not much more than a ebay one (I think the last one I bought was about £6)  they will last longer, the sensors are used on lots of cars so you should have no problem getting a new one from VW.

If there is a mark/scratch on the surface of the head where the sensor fits try to file it flat carefully.

How do they work? Will a broken sender not send a signal at all to the dash? Do you guys think that it's definitely a sender problem instead of an actual oil problem? For instance if I fit a sensor and it wasn't working correctly what would happen, is that when I'm getting my light? 

I was at the main dealers (stealers) £17.40 for a sensor but I didn't know which one to get one was blue with 0.25  bar one was black with 1.4 bar and white with 1.8 bar Which one am I supposed to get it's the top low pressure sensor that I'm after on the side of my DX block 1.8 gti cabriolet 1987 

They have gone up in price since I last bought one  The Vw one may last longer than a repo one but as always it up to you which one you buy.

I would still try another switch, I have read about problems with repo switches as some seem to work and some no so well.

I've got a topran one fitted to my Scirocco and it seems to work fine.

Blue switch is what you need, that is what is fitted to my 1988 DX Gti and my 1978 Mk1 Scirocco.

It should come with a new washer if not always fit a new 1 as they are pence for a copper washer.

http://www.ebay.co.uk/itm/VW-T4-Engine-Oil-Pressure-Switch-Blue-028919081D-Also-AUDI-LT-MK1-Golf-German-/141890413736?hash=item210953e4a8:g:xnEAAOSwJb9Wq50W

Right I shall, I've got your link and I've ordered it.. in the meantime I'm using the old switch… it had 50880 written on it and the light was out when I fitted that,  I've driven it and no warning light at all lol, it flashed twice on start up then went off, my question is how do they work Haha the low pressure switch I mean ? Could the warning light be off because it's broken? And the light flashed at low rpm with the other switch because it worked? Confused.com 

The light flashes be cause the switch is detecting less than .3 bar oil pressure.

Now the Switch is preset that is why there are different versions.  

The Switch powers or actually Grounds the control unit that is inside the speed unit.

The controller has 2 inputs and a Speed Sense.
It will detect and flash for low pressure at idle.

It will flash and Buzz at High RPM Low pressure detect.

If the unit is wonky, then the sender senses wrong and flashes at low idle….  

I personally have seen this on my car when the Sender (CAN) on the head went flakey.  The Replacement I ordered off of ebay did the same, and Getting the High Priced Sensor at a Dealer solved the issue.

I have also seen the blinky light from Hades when I was breaking in a new Crank and used a Thinner oil as in 10W30, or with 20W50 and a Generic Filter.  

I have never seen it BLH (Blinky Light From Hades) with a good filter running Castrol 20W50.  

I have also seen it on my Car when the 36m oil pumps pressure relief valve got stuck.

Now for reference I live in Atlanta Ga, where in the Summer I have road temps @ 130F when the car is rolling down the road and stopped with a thinner weight oil I would see issues.  

I have been using 20W50 or 10w40 in my cars since the 70's when I lived in Illinois at -20F with no issues…

The DOPS (dynamic oil pressure system) is a little wonky at best.  They placed the Oil Pressure gauge on the Cabriolets at the Low end of the system, and it can cause sense issues.

Since everything on the Cabbies /Golfs are electrical they may not be a true measure of your system.  

IE: British Leyland used a True Mechanical Gauge for oil pressure that screw in to the block and measured the pressure at the pump.

Vw uses a electrical sensor, at the high end of the oil chain where the weakest pressure is obtained.

So if you are in Doubt, then I suggest that you install a Mechanical Gauge and Verify that you have an issue with "True gauge".  There are quite a few connections between the electrical senders, and the Cluster.

If you replaced all the bits, and didn't change the oil pump, well…… Oil pumps have an internal pressure relief that can get stuck open and then your pump will loose pressure at idle.

If you are truly worried, you can upgrade your oil pump from the 30mm geared pump to the 36mm geared pump, to increase flow, and volume.  You will have to have longer bolts to mount it, and take the pickup tube off your old pump and mount it to the new as the taller pumps pickup tube will prevent the Oil Pan from attaching.  

I have also installed a External Oil Cooler as on the 90's Cabriolets (digi) they stopped using the Water/Oil cooler.  Which was funny as they still used it on the Passats, and Golfs in the 90's.  As I noticed my oil temp was skyrocketing on a 85 degree day running at 80mph with the air on (Automatic)…  

Worried about engine/sensors, use a Mechanical Gauge to Validate what your oil is doing, once you find out, then you can make changes that are necessary.  

We can make Assumptions and change bits and pieces and miss the overall cause.  Test, Validate, and Verify before Jumping…..off the cliff.

Thank you for that, 

Okay so I changed my oil pump when I did my piston rings as I have to remove it to get the con rods out on the 3rd and 4th piston so I thought while I'm down their I'll change it. As I changed it I primed to pump with 10w40 part synthetic oil by pouring it into the top and just slightly rotating the shaft. I also oileded the shaft and pushed it up until the home, lined up the two bolt holes and tightened them up. Does that sound like I've done that correctly I'm thinking of upgrading my oil cooler to s front mount. Can you give me any advice on how to do this. Pictures on how to do it would be great. At the moment I have a Mann filter installed underneath a square oil cooler which coolant goes through on the top of it with the two tubes. 

P.s what oil pressure should I be seeing at the top end that's decent for when I fit a mechanical gauge, I'm wondering whether I can put an oil pressure gauge where those three gauges are in the centre console (the circular Ines) and then running it like that so I always know what gauge it is. 

P.s thanks again for the help. My car is in a garage at the moment and the mechanic didn't seem to be listening much on the phone. It's having a new back box fitted because it was rotted and blowing. It sounded like a hurricane coming down the road.  

From the Sound of it you did install it correctly.  But then was it the 30mm or 36mm gears?

I have a How I installed an external oil cooler in the link at my signature line, I used Scavenged Parts from a Wrecking yard  I show pictures of how I did it and what the parts for it came from.

To install it you will remove your Water Cooled one, which is more of a Oil Stabilizer, than a true cooler.

You will rid yourself of the "T" hose on the Cooler and go with the 90 cabriolets water pump to Heater hard line.

You will need to remove and Plug your water outlet flange on the head or replace it with one from a Diesel or non-water cooled oil cooler that doesn't have the extra port for the cooler.  

Here is a water oil cooler flange vs non-oil cooler flange.
I talk about it because of the Plastic flanges I had on my 92, and 93 Digifants that I had to replace at least once a year, so I finally figured out how to replace most of my plastic parts with Metal ones.

From this:


To this:


The Link on my signature is where all my how to's are by category, ie: electrical, engine, interior……

For oil pressures there is a good write up in the Bentley as to what "Normal" pressures are and they are measured with a Mechanical Gauge.

this is the kind of oil cooler I have on mine, I've looked at Your technical how too's and wow they are so cool! 
I looked at the one with the cooler too that you did from the scrap yard and was wondering if I too could do that on mine? I was a bit lost on how I'd feed it 

So I've done some digging around and this is what I want to do to my oil cooler set up, can you give me pointers please ?! 
I'll post pictures below of what I'm after doing 
My confusion is how oil is fed to the cooler I'm wanting to fit? Is it fed thru the pipe that goes to the oil filter or something? A diagram of the way oil flows would be cool ! I know I'm annoying but I just love tinkering haha

Why do you want to change to an air feed oil cooler?

The water type cooler is a better system as it heats the oil up when the engine is cold and cools it when it's hot.
The air feed oil cooler will not work when the car is not moving or moving slowly.

VW are still using the water feed coolers in there newer cars.
It seems a lot of work/effort and expense for no real gain.

As long as you use the correct antifreeze mix and regular changes to the coolant you should not have much trouble with the water cooler.

As the saying goes…….. if it ain't broke don't fix it

This is just my thoughts.. 

Fair point!! 

I wanted to run both, I'll post a pic.. green highlighted water cooler and red highlighting the sandwich leading to the air cooler.. I don't really trust the dinky lil water oil cooler on its own, and think it can run both from looking at the pic.. I was gonna mount it with the rad so the if I'm stopped the oil will cool from the fan, I want it for drives to seaside in summer with my friends etc I just wonder how that guy did it and what he used 

I do get if it ain't broke don't fix it though ! And respect fully what you mean.

Thank you for reply 

140 degrees C is getting towards to danger point of oil.

115 degrees C is the top my oil got in the Golf on a couple of track days, quick driving on a motorway.

120 degrees C in my Mk1 Scirocco with NO oil cooler fitted and driving at 4500rpm on a motorway for about 2 hours on a hot sunny day.

I think 2 coolers is a bit over kill for a road car, fine for a track day car.

Fair point!! 

I wanted to run both, I'll post a pic.. green highlighted water cooler and red highlighting the sandwich leading to the air cooler.. I don't really trust the dinky lil water oil cooler on its own, and think it can run both from looking at the pic.. I was gonna mount it with the rad so the if I'm stopped the oil will cool from the fan, I want it for drives to seaside in summer with my friends etc I just wonder how that guy did it and what he used 

I do get if it ain't broke don't fix it though ! And respect fully what you mean.

Thank you for reply 

sorry I posted that twice, yeah you are right man! Ok help me find an oil cooler for my car if you would ? My reg is D636mub mk1 gti 8 v cabriolet 1.8 I'm struggling to find one on Euro car parts, they've got them for mk2 that look similar but different dimensions so I just need the dimensions I guess