Cooling engine

Hi Bernie

I had a similar problem with my IM.  My engine compartment (and engine) was getting very hot, even when the outside temperature wasn't that high.

I installed a very simple bracket, with two bolts, so I could drive with the hood open.  I could connect or disconnect the bracket in a couple of minutes.

The difference in engine bay temperatures was significant.

After driving with the engine lid closed, I couldn't rest my hand on anything in the engine bay, including the shroud and air filters.  After driving with the hood open 4 inches, I could rest my hand on the shroud, air filters, and alternator.

Big difference.

Presently, I'm installing a vent on either side of my throttle bodies, to increase the airflow.  This may lower the overall engine bay temperature, but if it doesn't I'll continue to pop the hood 4 inches when going for long, high speed drives.

First, where is this oil cooler mounted?

Put the front firewall hole in front of the fan inlet instead of above the fan shroud. More air will reach a lower hole than a higher hole and the air won't then have to then make two 90 degree turns to get into the fan.

Do not cut holes into the engine compartment bottom panels. It's specifically sealed off to prevent hot air from coming back into the top of the engine compartment. You'll make the overheating problem worse if you do.

Do you have all the engine cooling tin in place?

Yeah, and to that point, do you have all of the heat shields in place to prevent cross-over of exhaust heat from below to above the heads?  Looking into the engine bay, you should not be able to see the ground at all, just horizontal sheet metal all around the engine.

Same thing for the firewall - there should be something closing the area between the firewall and the horizontal heat shields.

As Justin asked, both where is your current external oil cooler mounted and how is it connected to the engine?  "Full Flow" connections or something coming out of/in to the oil pump cover?  

Does the engine also have the original, VW internal cooling tower?

Lastly, some of the cars with larger engines have cut vent holes into the area right behind the license plate.  That way they can act as a vent and are unobtrusive.

Hi all,

 importantly thanks for for the feedback.

All of the tin ware is in place and I'm currently looking at adding the corrugated metal - similiar to the turbo wrap - around the exhaust near the heads.

The oil cooler is just in front of the transaxle with a shroud and fan.

I have purchased a laser temp gun and will run temps on the exhaust, heads etc to see just how hot it is actually getting.

At the moment I'm measuring off an internal temp gauge and it may not be accurate.

Bill, how long would it take you to take those wedges out and close the hood?

Bernie  " Wedges " is not the answer but a Band Aid fix to a very serious cooling issue, start by confirming the fan shroud thermostat operation if you have one, something as simple as belt slippage, fan intake blockage or even a shop rag sucked in under motor head tin, motor to engine bay seal in place, timing...and so forth. 

The engine is a new build.

The entire car has now been restored with new interior, paint and engine and we have been over every bit of the 356

I'll go back and go over the engine and fan etc. yes there maybe something wrong there. The tune up I'm told is spot on.  But I think we will re check it again.

I have a laser temp gun and will do some roadside stops and check the actual temps against the gauge. The dash gauge may be wrong - sender.

Thanks for the advice - 

cheers

bernie 

Unknowingly, I had shop rag get sucked into the fan and a large piece came to rest on top the 1-2 head side...that took a while do discover my heat issue.

Bernie, I've used a temperature gun on my engine and found the readings to be very close to my dip-stick thermometer.  Both showed that my oil temperature gauge was way off.  When my dash gauge showed 210 the engine oil temperature was actually 240

I found out I had the wrong VDO sending unit.

While you're on the ground taking readings with your temperature gun also take a few cylinder head readings.  Note this has to be done as soon as you stop, because as soon as you turn off the engine it will start to cool down and your readings won't be accurate.

Ron

Thank you, yes I ll get the temperature checks done straight off.

I'll check heads, plug area and exhaust outlet points. The gauge on dash will prove either accurate or high reading.

Just a thought on this-do you remember the old diagnostic routine-''is there petrol in the tank'' then the diagnostics go deeper? It is probably a stupid question but are all the correct holes cut out of the underside of the engine lid to allow air into the back of the fan? It just makes me wonder when you say it runs cooler with the lid open.

Red,

It's an aerodynamic thing. The vents in the deck-lid just don't do much of anything to feed air to the engine.

Perhaps Justin will pipe up on the "why", but the anecdotal evidence from people who drive air-cooled speedsters in very hot climates (like Australia, Las Vegas, etc.) suggest that popping the deck-lid makes more difference than any other cooling change a guy can make.

I've gone to pretty great lengths to upgrade my cooling system in any way possible (short of running oil coolers up front, which I may do some day- since I'm dry-sumped), and I'm good 99% of the time- but driving 80+ mph through the desert puts a load on that overwhelms what I've got. On my "big trip" to CA last year, popping the deck-lid in the desert lowered my oil temps from "don't drive" to "wow, that's pretty hot".

Some sort of NASA duct set-up would certainly help, if they weren't so pitiably ugly. Henry Reisner cuts out the glass behind the license plate on the 6-cyl cars to feed them more air- I may do that someday as well.

More air solves a lot of overheating issues. Figuring out a way to feed the engine more air, without messing up the lines of the car- that's the trick.

Remember, with our air cooled cars were dealing with two important temperatures: oil and cylinder head.

On my IM even though I had high oil temperatures my cylinder head temperatures were normal (using a Westach gauge).

Thanks for the feedback and discussion.

The area around the motor should be sealed from the exhaust. Most kit manufacturers use a thin sheet of fiberglass with foam on the edge contacting the enine tin. If yours has gaps or not sealing well the exhaust heat is being sucked in thru both your fan and the carbs which will cause your issues.

the other area is the oil cooler. You mention it is in front of the trans. I noticed several cars with them mounted above the trans on the panel behind the seats. If this is the case that may be part of the problem.  The engine fan is sucking the hot air from the oil cooler.  Mount the cooler elsewhere. 

One other cause  maybe the lack of air getting into the engine compartment. I presently have a car in the shop that has mirror finished stainless on all the panels inside the engine compartment. Which seals the hole behind the fan for any fresh air and they to have issues of the engine running hot.   

Keep in mind that not only does the fan suck air to cool the engine it is also competing with your dual carbs for fresh cool air.

most kit manufactures know this and use the smaller diameter fan Pulley from a 356 to speed up the fan speed In order to assist in the cooling.

Thanks Anthony for the feedback.

i have me cooler well forward of the trans and it has a fan.

i think looking back over the discussion and feedback here, I will re check the entire engine bay to ensure its air tight from the exhaust.

i have asked my shop to wrap the exhaust for me now and I have a new set of crinkle finish heat plates going in. This is the plate used in high temperature situation such as turbo etc.

i will be using the laser temperature gun to check actual temperatures at the exhaust, heads and plug areas of the four barrels to make sure my temperature gauge is working correctly.

We are also looking at bringing air up through the back area into the fan from under the car via a brake duct and brake cooling tube..

thanks again.

Do you have an 8" diameter hole in the firewall right in front of the fan's air intake?

You could locate a cooler(s) with fan behind the front lights angled and create a metal scoop to suck air into the coolers. That should solve the oil temp Ray

Well there won't be much action tonight on the list... the Carlisle event is on. 

I already noticed that.  Apparently our East Coast brethren post more than us West Coasters.

Thanks

I will check if there is a hole ahead of the fan shroud.

i will try and bring fresh air up in into here

Lots of great info (and experience) here. I don't think you have to actually "duct" air to the hole in the front firewall of the engine compartment, Bernie, as the pressure differential between above and below the car fills the area around the transaxle with positively pressurized air (I've read that with a beetle body the airstream under the car can be as much as 2psi higher than over the top/back window and engine lid area) and automatically flows into the engine compartment with the engine running and the car at speed. Looking at the side profile of a speedster, it's somewhat wing shaped (flat bottom, curved top), so I think our cars are similar in that regard. As (I think) Justin said, position the hole in the firewall low in front of the fan so it's not having to turn corners to get there. A 6" round hole adds 27 1/4 sq. in. of air intake and 7" adds 38 1/2 sq. in. 

Looking at my engine compartment (an older Intermeccanica), if I ever get it up and running, I will probably also add 4" holes in the firewall directly in front of the air cleaners; a pair of dual carburetors will ingest somewhere between 300 to over 1,000cfm at full throttle, and these cars need all the air intake help we can give them! Ron's idea to cut holes in the inner wheelwells to feed the carbs also has merit, as this has been done in high- perf beetles with success. Gene Berg (back in the '80's) claimed that not only did it add air intake, it made it easier to change plugs (and also adjust carbs and clean jets with IDF's).

Stan (and a couple others, I think) have noted that adding a big hole in the firewall didn't have the effect they had hoped for, and I think the reason for that is that now that we've figured out how to get a lot of air into the engine compartment, we've now got to get it out. Ron, Stan, and others have found that lifting the engine lid cools the engine down somewhat, and what I think is happening is it's removing radiated heat from the hot engine parts by letting pressurized air coming in from the firewall and flow through the engine compartment (and out the engine lid opening). As Ron said- "After driving with the engine lid closed, I couldn't rest my hand on anything in the engine bay, including the shroud and air filters.  After driving with the hood open 4 inches, I could rest my hand on the shroud, air filters, and alternator. Big difference."

Now, how to get all this air out? We have air coming in from the front, the exhaust area has to be sealed off from the engine compartment (or the fan and carbs will be recirculating heat from the exhaust and spent cooling air), and the engine lid will not allow nearly the volume to exit that the engine compartment requires without us performing major surgery to the inner rain shield (I think mine has about 12 sq.in. for venting), so what do we do? I think my lid can be modified for another (maybe) 10 or so sq.in., but that's not nearly enough if you want to be able to cruise down the highway with the engine lid closed. Stan mentioned vent holes underneath the licence plate, and this has been done in beetles with great success- VW Mexico even used (I think; someone please correct me if I'm wrong) a thermostatically controlled door under the licence plate during the last few years of beetle production for the same reason.

"...opening a few air outlets down on the panels near the lower pulleys..." I think you were on the right track in your first post, Bernie; it just needs to be expanded on. Those holes (4"? 5"?- to get enough volume for solid air movement through the engine compartment) would need some duct work (simple bendable tubing, I think) to release the air into the airflow under the car (lower than the exhaust and towards the wheelwells, maybe?). I think you might be on the something here...

We have to remember that we're on uncharted ground here; a lot of us are at power levels (and the waste heat these larger, more powerful engines create) the engineers at VW (or Porsche, for that matter) never envisioned (or had to deal with). Thinking outside the box (and all the way through) is what's required, 'cause nothing either factory did with this era of car applies.

One last thing- a pic (actually 2) of a road racing Speedster. I know I've posted this pic before, but LOOK AGAIN AT THE SIZE OF THE INTAKE TUBE TO THE FIREWALL! I'm sure they're looking for as much life out of the engine as possible, as that thing is probably at a power level (150? 160hp?) that's not nearly measured in thousands of miles, and those babies ain't cheap to rebuild! And I'll bet that engine lid is carved up to let as much air through the engine compartment as possible...

Or, you could roll with a 356 "B"-style engine cover, like this:

BTW:  In the realm of "Unobtanium, this particular roadster is owned by a gentleman in our local club, and is one of only 200 made to this spec (including the somewhat higher-performance engine).  The wider view of the rear shows the larger-than-usual exhaust tips protruding through his slightly larger bumperettes.  All of this is wicked cool, along with a LOT of other, very subtle differences......And trust me, this car is way beyond "stunning"!

Thanks again for the feedback.

I have two brake ducts and four feet of brake tube cooling line.

That's the flexi red tube.

I think I'll work on getting air up into the engine compartment near the carbies, but directed into the carbies along with the main air flow into the back of the shroud.

I'm definitely wrapping the exhaust and installing crinkle heat shield between the exhaust and barrels. 

Thanks guys again.