External Oil Cooler By-passed on RAT Type 4

The VW engine, both type 1 and type 4, have a so-called "internal cooler" that sits on top of the engine inside of the fan shroud.  The flow of oil through that internal cooler is controlled by pressure valve in the bottom of the case.   The temperature is controlled by oil pressure:  When the oil is cold it is thicker so the valve by-passes the cooler, when it warms up and gets thinner and the oil pressure drops, the valve begins to route oil through the cooler and that's how it maintains a range of oil temp.

When the case is tapped for an external oil cooler, you tap right into the oil gallery as a return (you get the oil from the cover of the oil pump) so you've just by-passed the oil pressure valve.  That means that all of the oil goes through the external cooler all of the time.  Of course, this depends on exactly where the oil is gotten from and returned to, but you get the idea.

We get around the over-cooling problem by installing a thermo switch in the external oil line which by-passes the cooler under 180° and routes the oil through the cooler over 180°.   It doesn't look like you have that oil switch on your car.

So we get back to one of your questions - was it running too cool and they eliminated the cooler?  Possibly, but we don't know how much of the upright cooling system (fan shroud, engine tins, thermostat and air vanes inside of the shroud) you have in there.  If you search on here about "cooling" you'll get an evening's worth of reading and know what I'm talking about - the engines in these cars are picky about having the proper engine tins installed.  Also, that is a "bargain basement" cooler in there, because it doesn't have a powered fan to force air through the cooler.  Not having a fan makes me wonder how well it might cool in the first place - probably not much.  Most of us (a majority, for sure) are running either Setrab or DeRale coolers with 12v fans on them and they work well, especially if located in the left rear wheel well.

Bear in mind that the original type 4 engine had a "pancake" cooling system which was quite different from yours.  While we've successfully adapted the Type 1 cooling system to the Type 4, cooling anything over 2 liters is always tougher to cool as it taxes the fan system a lot. 

So......You could pull the cooler and get it tested to see if it is any good or just spring for a Setrab or DeRale 16-pass fan assisted cooler, and then install an external thermostatic Oil valve (someone will recommend one they like, I'm sure....Some of us run MoCal units) and you would be good to go.  The other thing to make sure of is that ALL of the proper engine tins, heat shields, thermostat and air vanes are installed and working properly.   All THAT would make it bullet-proof.

Gordon,

Wow, Great detailed explanation and a great solution.  I haven't pulled the DTM Cooling Shroud, but I pulled the fan belt off and the generator cooling fan appears to spin well, smooth and quiet.  Also, the oil cooler that exits through the top of the shroud looks good and there aren't any oil leaks coming from the lines.  All the tines were in place prior to engine removal. I removed them to get the engine out.

The car does have a temperature gauge inside, but I am not sure how accurate it is.  The previous owners said that the car ran cool and that overheating was not a problem. I also need to figure out if it is reading the oil temperature (my guess) or possibly head temperature. I did some searching on Jake Raby's site and it does appear the the possibility to run too cool does exist.  It makes complete sense at this point to pull the external cooler and have it checked, and to add an external thermostatic oil valve.

Thank you for providing great information on the cooling system, and a solution for my by passed external cooler.  Is there a good cost effective way to check the oil temperature so I can determine if my internal gauge is accurate?

Again, Thanks for the help!

Bill

Type 4 engines in Speedster (and beetles) don't generally need an extra cooler, as the engine was originally designed to push the rather boxy (and heavy bus) around and it just never has to to work that hard in the lighter (and more aerodynamic) cars. The possibility of the engine never reaching operating temps does exist (which accelerates internal engine wear), so if you are going to keep the cooler there needs to be a thermostat plumbed in front of it. You could use a candy thermometer to compare readings for your gauge's accuracy. Al

PS- follow the wiring from the gauge to the sensor to figure out what it's measuring; my guess is it's oil temperature. Some pics of the engine compartment would help.

He's got a Raby Type 4, Gordon, with a DTM shroud.

From the pictures, I can't tell if it's a V1 or V2 DTM. The V1 had a big hose snaking around back to a Type 4 oil cooler with hoses leading to and from. The V2 has no hose and no cooler. It'd be good to know what you've got.

If it's a V1, I'm betting Al is right-- the 96 plate cooler probably isn't needed. Perhaps it was left over from a previous T1 iteration. Perhaps the fin deformation in the center of the cooler is a leak. It's hard to know without more information. A good temperature gauge would be nice to have.

If you do want the aux cooler, you most definitely need an oil thermostat (as Gordon explained). Far and away the best choice is a MoCal "sandwich plate" thermostat (Google it). No matter what you get, you want it to bypass the cooler until the oil is up to about 175-180*, then send it through the cooler.

Thanks Al,

I took a look at the Temp Gauge it say's oil on it.  I believe the picture below is the sensor.  I am beginning to think the Oil cooler was disconnected because it wasn't needed and the oil temp may have been a little too cool with it in place. Perhaps the oil cooler was in use when the car had the original Type 1?  I will look into purchasing a Candy Thermometer.  Thanks for the advice!

Bill

Thanks Stan,

In reviewing post on different websites, and reading the RAT ID on my Engine Block.  It looks like my engine was built in 2002.  I believe it has the original DTM shroud with Type 4 cooler.  It looks like DTM version 2.0 came out in 2006.  I have included a better picture for your review.  Thanks Stan for the great Intel.

Bill

I just received an email reply from the previous owner:

Thanks for all your input!

See! You didn't need us at all, Bill!

You are correct-- that's a V1. BTW: Good score on the RAT Type 4. That's a big, big deal.

Nice problem to have!

Ah, now that I've got the ears of some very knowledgeable 'oil cooling' gurus maybe they can explain what I've only recently come to realize is an unusual system....I've got not one but two fan cooled Setrab units tucked up under both sides of my rear wheel wells!... Is anyone familiar with such a system?  The previous owner lived in Oregon so the 2110cc  wasn't operated in a hot desert environment. 

Well, I am be no means any kind of expert here, and can certainly follow what those who are experts (Gordon, et al.) say about this or that.  All I can offer is that I have a 2332 T1 with what I was told is a stock VW oil cooler in the dog house shroud.  So far as I can tell, the oil is cooled as it should be.  Hottest normal running temp on a hot day is needle straight up.  Most times i rarely get much past the little green region on the left.  To me, all this stuff about external oil coolers is just guys having fun with the hobby, listening to somebody who heard from somebody that cooler was better.  Maybe different for Type IV's  vs. Type 1s.  I dunno.  If you are going to race, well that changes the game for sure.

That said, I do believe I have run up against a little bit too high head temperature once or twice.  Not sure where oil temp comes into that picture -- sounds more like just not enough air in just the right place.  Oil temp and head temp on these engines seems to me to be mostly unrelated.

And a cast iron pipe fitting??  Really?  And this from the guy who has aluminum siding as engine tins.  ;-) 

Don't know, Carl, I've wondered about that since the first time you told me. Are there fans on the coolers? 

And Kelly, type 4's are quite a bit different than type 1 engines. The type 4 engines have shorter connecting rods and make more torque through the bottom end and lower midrange; they were designed some 30 years after the basic layout for the type 1 was drawn up and make use of newer technology (you have to remember that when the first beetle engine was designed and built, the automotive industry was still very much in it's infancy). The heads have some 23 or 25% more mass and the exhaust ports are out the bottom (and shorter) so they don't absorb as much heat and can deal with more heat before they are overloaded. The case, being aluminum, is sturdier, the oiling system is updated (it has all the Hoover mods already) and the main bearings are bigger so there's more area in the case to distribute the load. They're an improvement on the type 1.

I'm sure someone else will come up with more. Al

Carl:

Believe it or not, that was (is still?) a popular cooling method from Bernie Bergman - Yes, he could build you a BIG engine (over 1.9 liters he thought was big) and he had, IIRC, his own version of the Porsche 911 fan shroud that did not allow for the internal oil cooling tower.  Word back then was it didn't cool very well, so he talked customers into running a pair of external oil coolers that got their oil flow from an adapter bolted in place of the internal cooler.  He apparently has gone away from that adapter and now pulls the oil from the pump cover (a la Berg and others) but he's still pushing dual oil coolers on his site:  

http://www.bergmannvw.net/Webs...oil_cooler_kits.html

I get a kick out of him shipping a small oil pump "free of charge" (yeah, I believe THAT!) so you can connect everything on your bench and pump oil through the coolers to "remove any debris before installation".  What?  He couldn't have done that for you or had the cooler manufacturer do it before shipping debris-filled coolers out?   WTF?

All I can suggest is to trace back the oil lines and see where they go.  You should have an oil thermostat in there somewhere re-directing the oil flow depending on whether the engine needs the additional cooling or not.

You'll also have to give us a little more info on the coolers that you have - approximate size (L,W, thickness) and whether they have fans or not.

Speedstahguy standing by.......

Whats the RAT ID on this engine? I know by heart most combos of these engines going back that far, and original purchaser's names too. That one looks like one of two engines I built for Roger Dawson. If so, its a 2270 and more than likely it will need some auxiliary oil cooling.

Where's the oil temperature sensor located? The V1 DTM will suffice for some engines, while others will require an auxiliary oil cooler in higher ambient temperatures, or when seeing long sustained runs. Gearing plays into this heavily, as well.

Thanks Gordon...Curious mystery solved !!!

Both coolers have fans. I don't have access right now to the speeder (up on jack stands at my friends garage/workshop...duh)  but I believe the surface area of the radiators is about 10x10" or 12x12" They fit snugly into that small body cavity behind the rear wheels.  I'll have to check on their 'thickness' and if and where I have an inline oil temperature 'dohicky'

I more I learn about how this motorized toy of mine functions - or is supposed to function - the more I realize how much I don't know...or was even aware of. Thank heavens for the Q&A's on this forum !!!

Years ago I had a 914 with 1,7L T4.  I added OEM gauges to center console.  Oil temp sender was mounted in what 914 guys call the TACO plate in the bottom of the engine.  The oil pressure used a dual sender (for dash idiot light and gauge) on top of the engine. I added another oil cooler when I added AC and went with bigger pistons and Weber carbs.  I also added a thermostatically (heat) controlled bypass switch to bypass added cooler in cold weather (was in NJ and N. VA then).

And so it goes . . .

Jake,

Sorry for the delay.  You are correct.  The RAT IV was purchased by Roger.  He did mention to me he purchased 2 motors.  I took a couple of pictures of the RAT ID.  It is a little hard to read the last 2 RAT ID #'s.  It would be great to know from your perspective if you believe the external cooler is necessary.  Thanks for your support.

P.S. Any other information you could provide me on my motor would be greatly appreciated.  Roger did not have any documentation on the car when I purchased it.

Bill S. posted:

Jake,

Sorry for the delay.  You are correct.  The RAT IV was purchased by Roger.  He did mention to me he purchased 2 motors.  I took a couple of pictures of the RAT ID.  It is a little hard to read the last 2 RAT ID #'s.  It would be great to know from your perspective if you believe the external cooler is necessary.  Thanks for your support.

P.S. Any other information you could provide me on my motor would be greatly appreciated.  Roger did not have any documentation on the car when I purchased it.

Last two numbers looks like a 20 making it a 2002 20. Possibly the year 2002 and the 20th motor??

Relooked photos of oil cooler - and just realized it is mounted way in the nose of the car.  That's  a long way to pump oil in big hoses.  It has to reduce velocity. I suspect source of those hoses is a sandwich fitting under the factory oil filter. I'd remover it or move cooler. A better place for the cooler is a rear wheel well or even above trans-axle.

I agree with Greg- that's a long way away from the engine for the cooler, and you're better off mounting it in the rear fenderwell. If you're feeding the engine air from a hole in the firewall (in front of the engine) though, then locating the auxiliary cooler above the transaxle will only preheat that air (not what you want to be doing) so again, in the rear fenderwell is a better place. The air going into the fan and carbs needs to be as close to ambient temp as possible. Al

Thanks guys, I agree the last 2 numbers look to be 20 on the RAT ID.  The hoses for the external oil cooler are hooked to the Type 4 motor and an external oil filter behind the engine firewall. Oil hoses connect to the fitting on the lower left of the motor.  I have them covered in white plastic and red tape for cleaning. Bill