chuckster

I have a '74 2.0 with a cooler placed in the front bonnet. There is oil going to the front cooler but it seems not all the oil is flowing through the cooler. There is no thermostat any where in the line. I have a check valve in line for the accusump. No doubt the valve is installed properly. My questions are: Is it possible the valve at the oil filter that routes oil in case the filter clugs is opening allowing oil to bypass the filter and sandwich plate? If this is happening what is the solution? Is the restriction from 12' of aeroquip lines and a cooler is causing enough pressure to open the oil filter valve? Thanks!!!

JPIII

I don't know much about the "sandwich adaptor" used for the type 4 set-up, but I do know a bit about cold oil,25 feet of lines, and front coolers. The restrictions caused by the lines and cooler, combined with cold oil, can be VERY high. I blew a high quality cooler learning this. Mine is a 6 and that oil pump is very powerful. I would guess that it was generating somewhere around 150 psi when the cooler surrendered. Yours well may be capable of opening the filter bypass depending on the internal plumbing of the adaptor....I've never had my grubbies on one, so I dunno exactly how they work.

As for a solution, a thermostat incrementally opens as it warms, thus slowly pushes the cold oil thru the aux cooler system while still mostly) bypassing it. As I figure it, it's a matter of volume. Lower volume creates less backpressure.As everything warms up, the backpressure is reduced, the thermo opens fully and all is well in 914 land. This assumes a high quaility thermostat like Troutmans, which uses the thermo from a 911 engine. It also has a pressure bypass, thank God, or my motor would be toast.

chuckster

I don't have a thermostat in the line. I figure the little spring & ball bearing in the filter bypass is opening. And very little oil is getting to the cooler. By the way is your 914 an original six.

Thanks for the reply JPIII.

chuckster

I just noticed your sig. Obviously, you have a conversion. I am considering a converse for my 914. First I want to solve my current problems before taking on even bigger challenges.

JPIII

I was suggesting to use a thermostat to fix the problem......been wrong before, tho.

JPIII

chuckster

AAAh Ok so putting a thermostat in line might solve the problem. I was thinking that would add even more restriction. Infact, it seems as the oil gets warmer there is actually less oil flowing to the cooler. The more I think about this, the less I seem to understand what the problem is. The oil filter bypass valve is a pretty small hole and I would think this would have more restriction than the larger lines. Then again I'm passing the oil through a cooler also. I'm wondering is there any way to block that bypass valve, at least for track use and testing.
Anyway thanks for the input. If you have other thoughts please let me know. Thanks again.

JPIII

The thermostat plumbs to the output side of your adaptor, input side, and in and out of the cooler.
When cold, the oil goes to the thermo and right back to the input side of your adaptor.....a quick U turn, thus, low pack pressure. As the oil heats, the thermo slowy opens,pushing a small volume of oil thru the cooler while continuing to push the majority back to the input side. As the oil heats, it looses viscosity and less back pressure is created. It may take 10 minutes or more of driving to get the thermo fully open and moving all the oil thru the cooler. My 6 takes 15 to 20 minutes to accomplish this......assuming the oil gets over 185 deg. Often, depending on the ambient temperature (or how bad I'm beating on it), the engine oil cooler is up to the task of cooling the oil so the Aux cooler is bypassed. When fully open, the thremo diverts all the oil thru the aux cooler.....subject to its internal pressure relief and that of the filter(in your case. My filter is downstream of the thermo). By them the oil is hot and the back pressure is low or at least, managable.

All this assumes you have properly sized lines & fittings. 12AN would be the minimun size I would use. Small hose=high back pressure.

As you have described it, your aux cooler is not being used "as required" by temperature. Without a thermo,a 911 motor, with that killer oil pump,that can get ya a blown aux cooler.

Cupcar

Best thermostat is a Troutman which uses a factory 911 engine style Behr thermostat. With this unit there is essentially no restriction and the resistance across the thermostat is constant between full open and full closed. A very nice piece. Also I flare (Funnel) the outbound AN fittings before I screw them into the troutman housing to improve flow.

chuckster

Thanks for all the input. I orginally had a troutman thermostat in line. When it was determined that there was insufficient oil getting to the cooler. It was removed. Of course removing the thermostat didnt fix the problem.

I pulled the cooler lines started the car. The oil was flowing but not in the volume expected. My bother-in-law, Pete put his finger over the oil line to stop the flow. At this point, he figured there was a problem.

One problem was we had oil pressure with the line removed, about 20lbs. There should have been no oil pressure. Now with his finger over the line, the oil pressure built up to 40lbs no higher.

The question is where did the oil pressure come from if there was no oil flowing to the engine. The line is removed going back to the engine. We looked at the oil schematic for the engine. He noticed the oil pressure relief valve at the filter.

Pete has lots of experience working on Porsches. And has built many engines but not that many 914 motors. We didn't know where that release valve was for the oil filter.

I got up there to remove the sandwich plate thinking there was something wrong there. But there is nothing to go wrong with a sandwich plate, other than a restriction from a clug. When I pulled the sandwich plate... I found the release valve.

The valve seems to do be doing what it is designed to do. Opening if there is a restriction going through to the filter. And there is 10-12' of line and a big oil cooler in the way. So the oil finds the easiest route or in this case travels through two routes. This explains why we had some oil to the cooler and oil pressure when the line was disconnected.

My question is how do you bypass that valve so oil can flow only one way... through the cooler then to the filter? Pete knew many guys ran remote filters on their 914's... and of course 911's do this.

We knew there was a block off plate for the oil filter adapter. But I also wanted to know if there was some other alternative or how others had solved this problem.

Today while playing with a 2.0L on a bench. I pulled the cooler off and the adapter plate. And decide the quickest solution to the problem was to plug the valve.

This was pretty easy to do. A 5/8th or 16mm freeze plug fits in there perfectly. Nice press fit. Now the oil has only one way to flow... to the cooler and then back to the filter. I plugged where the oil enters the valve not the exit.

The real test will be next weekend at our DE. I am very confident this will be the solution until I get a proper block off plate and add a remote filter.

I apoligize for the lengthy response but this problem has been a plauge of this car for quite a long time. The previous owner had the same problem but didnt have the time or interest to solve the problem (he has many more interesting toys) And I'm very excited to maybe have finally found a solution. Thanks again for the input.


<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />