We just picked up a 79 vw camper van. It has an oil temp gauge and a cylinder head gauge. When we are on the freeway the cylinder head gauge runs between 260 and 340. This is near the top of the gauge. Is this a normal temp or is it running to hot. The oil temp seems fine(not high) The previous owner said he rebuilt the engine and that the cylinder head was warped in the previous engine. I don't want to repeat that history. Any input would be great. We are new to vws. Thank you
450* F is the lower edge of the plastic range for cast aluminum. Unlike iron which remains malleable throughout its plastic range, aluminum suffers from what's called 'white shortness,' meaning it becomes frangible prior to melting. Raise the temperature of your cast aluminum heads into the frangible range (ie, >450*F) subject them to stress (such as detonation) and you've just trashed the engine.
This is not especially worrisome in the Volkswagen because the stock cooling system has sufficient excess capacity so that the heads should never be subjected to temperatures in the frangible range without plenty of precursor warnings... such as the smell of burning oil, lotsa white smoke, etc. But if the vehicle is not properly maintained or if it has been subjected to any of the numerous 'improvements' hawked to the unwary, the situtation can arise.
The other side of the coin is that having installed a CHT gauge you are left with the question of its veracity. Instrumentation is normally calibrated prior to installation and verified after. With a system of unknown provenance about all a non-mechanic can do is cross their fingers.
Watch the "patterns" on your gauges. If the pattern suddenly changes, there's likely a problem. Hopefully you have a chance to get accustomed to the habits and patterns of your bus before you set out on a long journey with it. Long journies introduce new challenges and you should know what to expect from previous experience. My '79 bus varied up to 200 degree headtemp on freeway hills. It was hopped up with higher compression ratio (hotter) and I drove it like a wildman. Be ultra conservative. Use only the highest octane gas you can get and try to stick to the big name brands. When in really hot weather, either park it and go do something else during the peak heat hours or be very un-demanding of it. A helpful hint is when it seems to be getting too hot, lower road speed (lessen demand) and downshift whenever appropriate to increase engine speed and cooling air flow (fan speed is dependent upon engine speed, but don't be ridiculous!)
I used a 4 cylinder headtemp gauge so that I could watch for a problem occurring on any one cylinder (one cylinder misbehaving as relative to the others.) The actual numbers are not as important as the patterns and how the cylinder temps relate to each other. The reading relates to the difference in temp between the two ends of the sensor wire. If the connector end of the wire (not the sensor end) is 100 degrees hotter today than yesterday, the reading at the gauge will be 100 degrees lower for exactly the same head temperature at the sensor. If the temp is 25 degrees cooler (at the connector end) than it was yesterday, the exact same head temp will show as
25 degrees hotter on the gauge.
Any other questions? Just ask. E-mail me at snipped-for-privacy@yahoo.com
I have a CHT but the only place i could work out where to fit the sensor was on the bolt of the intakes. is this a suitable place would it be better on the exhaust port or not?
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