Aircooled overheating


New member
I've been to website many times and read most of info. - this is first question though. Any help would be much appreciated. I bought an 81 Westfalia 3 months ago and it has a VDO cylinder head temp gauge and an oil temp gauge. Mechanic tested gauges and they are accurate. Here's the problem- cylinder head temp goes to 450-500 on freeway at 55 mph and oil temp shoots up to 270. In city cylinder head temp stays at 350 but oil still goes to 250 plus. The tin is intact, oil cooler appears to be OK, and timing is on. I run 20w-50w. Thermostat is gone and the flaps are open. Two VW mechanics here in Phoenix have checked it out but haven't come up with a solution. Leak down results are #1- 25%, #2- 10%, #3- 15%, #4- 25%. One mechanic says O-rings are going bad but can't guarantee it will run any cooler if work is done. They say it is not running too lean. Can I take a close look at oil cooler/relief spring without pulling engine? I can't tell from Bentley manual. What else should I look at? All of these conditions exist during winter here, so imagine my problem when it's 108 degrees in August.

[ 02-16-2002: Message edited by: der_hund1 ]

[ 02-16-2002: Message edited by: Capt. Mike ]

Capt. Mike

First, put the thermostat back in; that's not the problem (if working and adjusted right) and the disadvantages (accelerated cold start wear) outweigh any perceived increase in engine cooling. VW was quite aware of the engine operating in hot climates; mechanics that think otherwise are just guessing at causes.

Your oil temperatures are not that extreme. See the posts on oils elswhere on the site. Admittedly, I prefer mine below 250°F, but up through 300°F is OK. See the posts under instruments about add-on gauges for my opinion of cylinder head temperature gauges. First, you are not measuring cylinder head temp, but spark plug temp -- VDO sensor is under the plug. 2nd, they are notoriously inaccurate and subject to damage every time the plugs go in & out. One or 2 spark plug changes is often all you can get out of a sensor before it is crushed or damaged to the point of unreliability.

Looking at the oil pressure relief valve is easy enough (with engine oil drainged) but understand its purpose is NOT to control flow to the oil cooler or filter, but the opposite -- to insure that if they are clogged, the oil bypasses them and goes direct to the engine to prevent oil starvation. So 'open' would not decrease engine flow.

When air-cooled temps are high, it's usually a function of loss of oil-cooling efficiency (dirty or film-covered oil cooler), dirty engine, especially fins covered with oil and road grime, or loss of seal in the cooling air flow. The engine to body seal is quite important in this regard.

The usual aftermarket correction for cooling problems is to increase the oil capacity and cooling since about much of the engine cooling is through the lubrication system. See the posts elsewhere on this topic as it also has trade-offs.


New member
Thanks for the quick reply. I'm going to investigate the oil cooler in more detail. Also, I failed to mention earlier that the heater duct work is missing from the heat exchangers to the heater blower. Post in oil cooler topic says these missing ducts could cause higher temps by recirculating hot air to engine. Ductwork looks to be easy enough to install- should I try it?

Capt. Mike

That can contribute but is not the more serious problem it would be in the Type II where the fan was in the engine comparment and connected to the heat exchanger before the manifolds. Thus an air channel. In a Vanagon air-cooled, the fan is in the front, so pulls air instead of pushes it like the Type II. The engine is expecting fresh, unheated air from the upper intakes, thus anything that breaks that seal and allows it to suck hot air from below increases operating temperatures. The fan doesn't know where the air is coming from thus the elaborate seals and ductwork to make sure it gets only the cool air from above the road surface and other engine heat.

However, the priniciple of the air-cooled heater is unchanged. The heat is always on, and that in itself is reducing temperatures by moving air through the heat exchangers and thus away from the exhaust. However, whether it goes into the ductwork for the heater or is dumped to ground depends on the air-flap control. Without the ductwork, the heat exhausts straight out the exchanger and has little venturi effect to carry it away, but with the ductwork and control flaps, it is dumped at an angle downward that carries it away from the engine while underway and also helps pull it out with that venturi effect.

Capt. Mike

Transferred to consolidate same topic.

Cutting vents for cooling.

ntkruse Junior Member posted April 30, 2004 05:21 PM

Hello, I have an 1980 westy, I was thinking of cutting a vent in the rear next to the liscense plate thinking it might help get some heat out, I live in the Northeast and traffic can be a problem sometimes. By doing this would I be altering the airflow from the vents or would it actually help bring in more air? Hope I posted this in the correct area if not forgive me.

tarmadilo Member posted May 01, 2004 11:09 PM

In general, mods like that are usually not effective. VW engineers did their damnedest to provide the most efficient airflow, and your '80 has the final (and therefore most evolved) aircooled VW engine. Keep it clean and full of oil, and you oughta be fine!

Cheers, Tim

Capt. Mike

Don't! The air-cooling part of the VW system is based on a pre-determined air flow, not just volume. The air intakes on an '80 are up high, on the side. Air from the rear would be sucking in the hot air from previous cooling and the exhaust system (Kamm effect), nevermind that it would be much closer to the road and maybe a dozen degrees hotter than factory intake.

Second, the flow is designed to force air from the cool intake air through the fan and out across the cylinders & heads in what is basically a sealed system. Thus the seal and all that ducting sheet-metal around the engine. Disturbing the flow is more likely to cause harm than assist.

A large portion of the VW's cooling is done by the oil and oil-cooler. Check for the proper oil & viscosity for your operating temperatures (See "Oil" topics elsewhere on the site) and reasonable driving technique and speeds, also posted elsewhere on the site (See Break-in comments in ENGINE forum.)


New member
air cooled with A/C

Greetings from Portland,
My 82 camper came with A/C, my question is this. How much drag does running the compressor put on the motor. We drive the camper from Oregon to Nevada in the spring and late summer and I try to only run the A/C while we are fairly level grades. Am I being over protective of the system? I use 20w-50 and the motor was completely overhauled 2000 miles ago. I run 55-60 on the freeway and never push it up a grade. The camper came to me with a “cylinder head temp gauge” that was dead, so I used the holes in the dash and installed a tachometer instead. My 84 has a factory tachometer that starts the redline at 5200 rpm’s so I set the tach in my camper for the same rpm’s, close enough? Thanks, Dan

Capt. Mike

The A/C load on an air-cooled can raise oil temps about 20°F on long pulls in hot weather. Not significant short-term. An oil temp guage is far more valuable than the cylinder head anyway -- read the topics on auxiliary gauges. I had a cylinder head & oil temp gauges on my '79. It basically reads spark plug temp since the sender is seated on the plug base. It responds slightly quicker but does not get reflect higher ops & oil temps since it normally runs hotter than oil would anyway. Excessive oil temps are more likely to damage the engine than cylinder head temps. In the worst conditions, I would shut my A/C off when the temp reached 260°F uphill and back on level or downhill. Very minor inconvenience a couple of hours on just a half-dozen days the entire time I owned the vehicle.
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Doc Brown

New member
Enumerating the engine tin

How many pieces of lower engine tin are there (and where are they?) on an 81? I was inspecting the cooling system for the first time and noticed that I could see the thermostat rigging (actually, I couldn't see the thermostat since it's not there, but the pulley is - replacing that is a project for another day....). Since other instructions indicate that lower tin has to be removed to check the thermostat, something must be missing. Discovering exactly what is missing is hampered by the fact that it is, by definition, not there....

Oh, and Bentley and even the parts fiche aren't terribly helpful in this regard, in their exploded diagrams it's difficult to see what really goes where.

Upper tin seems fine. At least, I can only see the road through the rust holes (which I'm patching up). I'm also blocking off things like the oil pressure sender hole which must have caused a heckuva leak in cooling air since it's right atop the oil cooler. Go-go aluminum duct tape!

The upper tin would seem to be more important than the lower in cooling the engine (empirically - my engine hasn't melted), once the air gets below the cylinders it's hot and on it's way to get vented (or used to heat the cabin - which ain't going to happen in my van since it also is missing the heater boxes - yet another project....) so presumably the lower tin is mainly to guide the air to an appropriate location not to be used again for cooling. It's remotely possible that cooling is better without it (less constriction of exhaust air, maybe a venturi effect under the van) but as the Captain says, 'stock is best' so that's where I'm headed. And that requires that I track down replacement tin. And that requires knowing what I'm looking for. So if some kindly soul could list the pieces, what they cover, where they attach, that would be exceedingly helpful.


New member
My 1982 Alternator / Fan Belt has broken. I am going to purchase a new belt and attempt to replace it tomorrow. If i am not able to replace it i am considering doing the drive (about 6 hours) without the belt in place (hooking up an extra battery to compensate for the alternator not working) - I need to catch a flight at 6am Monday morning.

Will this Damage my engine? the average air temperature at the moment is about 20'C where i am.

does any one have a link to a step by step guide on replacing a alternator belt on a 1982 Vanagon?