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Tue Jan 18, 2011 8:05 am

Anyone know of a thread that discusses the pro's cons of both of these? I searched but came up with 152 hits, none of which seemed to be what I was looking for. I recently bought a 69 Westy. Has 70k on a rebuild, although the 70k was put on over 30 years and only in the summer. It has an external oil cooler but it is mounted in the engine compartment. It will be at least a year before I can rebuild the motor, but I still want to drive her. The camping trips I want to go on go through mountain passes, many of those in Washington state. I figure the least I can do to protect the engine until I can rebuild is install either a head temp or oil temp gauge, but I get many differing opinions. It would be nice to have ease of installation in the discussion as well. Thanks.
Daddy

Tue Jan 18, 2011 8:12 am

I prefer all three oil temp, oil pressure and CHT.
The CHT lets you know about the engine temp right now vs oil temp which slowly builds...

Tue Jan 18, 2011 8:47 am

Yeah, all three would be best.

If you can only afford one, I would probably say oil temp.

You have an idiot light for oil pressure.

The CHT seems to stay in the allowable range as long as nothing is wrong with the motor or cooling equipment.

Oil Temp can creep up on a hill run, even if everything is working fine...that's probably more likely for you than a failure which will affect CHT.

IIRC if your T-2 engine loses the fan belt the generator light will come on. This mean pull over and shut down immediately since that belt drives the cooling fan as well as the generator. CHT might warn you of this, but the gen light is more likely to get your attention anyway.

Tue Jan 18, 2011 9:04 am

I'm sure your 152 hits has a lot of information. Main thing when reading anyones comments is determine what engine they have, a T-1 or a T-4. Different problems and different needs. T-4's need the CHT for monitoring but very few people want or have a need for CHT gauge on a T-1. We do not have head failures and issues like T-4's have. Additionallly putting on a CHT ring sender under the plug frequently causes problems with plug sealing and related issues. It's not worth it.
However oil temperature and oil pressure are very good to have. Both are highly recommended and few would recommend CHT for your engine. Monitoring oil pressure is probably the best and most meaningful way to monitor your engine temperature. Oil temp gauge will get you in trouble if you try to compare your readings with other folks readings since different methods of installing the sender gives totally different results. So the OT gauge is best for your own personal info. You will learn by experience how to "trend" the readings.
If you are concerned with engine heat it would be best to relocate your oil cooler. Installed in the engine compartment defeats it's purpose. First, it isn't getting ambient air but rather engine compartment temperature air. But maybe more of a problem is that any heat that gets pulled out of the cooler is heating the air going into the fan shroud. That fan air is what cools your engine and giving it hot air will cause your engine to run hotter.

BTW, I'm in the Arizona desert and don't use add-on coolers. Although have deep sumps. Do you have a thermostat controlled bypass system around your cooler? If not you may be doing more harm to your engine than if you got rid of your cooler. You don't want the cooling in cold weather.

Hope you notice that the two prior recommendations for CHT are people with T-4 engines. :wink:

Tue Jan 18, 2011 10:16 am

Hi, an option to consider is the Gene Berg oil temp dipstick. Cost is about $30. It can be a good diagnostic tool and/or compliment gauges to be installed later. This device really works and have used them for over 20 years in my bus and bugs.
On the subject of oil coolers, Gene Berg's '68 bus had a tube fin cooler mounted inside the engine compartment on the left side mounted vertically right above the are of the oil filter. He had the elephant ear plastic scoops on the left side. Don't remember if he had one on the right side. Don't think Gene had high oil/cht issues.
The owner of Bill and Steves VW Parts , in Lakewood, Ca, has a '71 panel with a mesa style cooler mounted a couple of feet forward of the left rear wheel and all plumbed with hundreds of $ of braided hose and AN fittings.
In lieu of a thermostat in the oil line, a simple wrap or blanket similar to the big rigs who can cover/uncover the front of their radiator opening.
Hope this helps or opens up more discussion, Bill

Tue Jan 18, 2011 10:20 am

oil temp is the gauge the VW forgot. they should have all had one. fancy porsches got them from the beginning.

the OT gauge in a bracket under the dash is the easier install between the two.
mount the sender in the oil drain plug in the middle of the sump plate and nowhere else.
run the wires and be done.

Tue Jan 18, 2011 11:19 am

And while I can not pinpoint one reason why, I strongly believe that engine condition will play a part in the overall oil temp/CHT debate.
True story, I have a '71 bus and a '74 bug. Both are relatively stock 1600 DP engines. I travel from Los Angeles over the Grapevine up to the Modesto area once each month. The bus slow down over the Grapevine and the Berg temp dipstick would lite my oil lite but as soon as the hill was behind me the lite would go out and never come on unless I picked the speed up to 65mph. On the other hand, the Bug, would lite the berg dipstick also over the hill but unless I stayed under 65 the lite would stay on! The oil lite would be on at idle. When I propped the deck lid open half way, I could run at 70mph with no lite comming on, but knew from a repair receipt in the glove box from the previous owner this engine had been overheated and had a quick temp repair. This might be considered comparing apples and pears but I still strongly believe that one diagnostic tool to have in ones toolbox is to be able to determine if an engine internal condition. In closing I don't mean static compression ratio or a couple of the other obvious items. Up for debate ?? Later amigos, Bill.

Tue Jan 18, 2011 1:58 pm

I have all three. Although it must be said I wouldn't have the CHT except that I was given it gratis by a work colleague who's a pilot and removed it from a plane he bought. Anyway, I'm not sure of it's merit in all honesty, I'm sure your searches revealed plenty of opinions regarding the accuracy of the VDO CHT gauge relative to the ambient temperature and I can certainly say that my experience chimes with others on this forum and beyond. I like the oil temp gauge best out of the three, pressure is useful too but whilst it is a function of temperature, it won't reveal temperature trends very easily on the move.

On a more positive note, 70K on a rebuild indicates the engine can't be in too bad shape!

Ant

Tue Jan 18, 2011 2:42 pm

cool karmann collected wrote: On a more positive note, 70K on a rebuild indicates the engine can't be in too bad shape!

Yes, it must have been a very good engine. But it is awful close to the end of it's life.

Tue Jan 18, 2011 2:56 pm

I cannot vouch for the effectiveness of a CHT gauge. I purchsaed the DD set up because of very good reviews. I installed the spark plug sender while the motor was out of the bus. After the install the gauge acted erratic so I called DD, the problem was the DD wires ran along side the tach. wires and were picking up the static signature from the tach. wire. So I ran them on opposite sides of the bus. That solved that problem but then the temps were no where near ball park. Turned out the spark plug sender had twisted on installation and was destroyed. I'll just drive without the CHT and use the oil temp gauge until the next time I pull the motor and mount the sender elsewhere. There is a very good thread on various methods to mount the sender on T-4s other than the spark plug. I've got a T-1.

Tue Jan 18, 2011 4:42 pm

Thanks for all the good info. I'd like to get the external oil cooler out but that would mean pulling the engine and reinstalling the stock cooler. Doesn't make much sense to me to do that until I rebuild the engine which will be a year from now. I like the idea of the dipstick gauge, which I had looked at before, but if I remember correctly you wire it to one of the other lights in the dash, seems like the oil pressure lite, which doesn't seem like a good idea either. Can anyone comment on what light you wire the dipstick light too? Thanks so much.
Daddy

Tue Jan 18, 2011 5:00 pm

Samba search for Berg dipstick. And find all the info. Or better yet go to Berg's website. No need to repeat it all again, and again. :wink:

Removing a stock cooler to add an external cooler is a bad deal. And if your engine had a doghouse cooler it is a real terrible deal. If you don't have the doghouse shroud make that a top priority when you do anything to your engine.

Tue Jan 18, 2011 5:11 pm

Go it figured out. Looks like even with the dipstick installed the light will read both oil pressure and temp. The external cooler was installed when I bought the bus. Seems like the dipstick might be the best way to go for my needs right now.

Tue Jan 18, 2011 5:48 pm

Here's a real cheap wireless oil temp setup for temporary use or permanent if your not fussy.

http://www.thesamba.com/vw/forum/viewtopic.php?t=309874&highlight=temp+gauge

jim

Wed Jan 19, 2011 10:43 am

I would say both, but if you can only get one I would get the OT as when your heads get hot they heat the oil fast and you should be able to see the trend as said by “Desertbusman”

Until I installed my (5) CHT sensors I had no idea how hard I was pushing my camper, I’m sure if I had a OT connected I would have suspected it…

Just an FYI, the CHT I installed showed how fast a cylinder head temp can change, just by lifting off the gas a little and changing the speed by 2-5 MPH the heads would go from close to 500F to the 420’s (still way too hot)

RPM Not connected CHT Cyl #1 off by 32 degrees

Installing my CHT was an eye opening experience ;0)

Doing 60-65MPH with a fully loaded Camper, in the 480’s head temps, the Berg oil temp sensor would start to flicker… I was running synthetic oil, Until I installed the (5) CHT I had no idea that my engine was running this hot before the Burg temp sensor was bilking

516F sensor JB welded in head a bit closer to exhaust Port next to spark plug on #3

:0(

Wed Jan 19, 2011 11:16 am

Lionheart thats nuts!
type 4 one cht. head temps around 350° f so I never bothered with the oil temp.hand on dipstick works for now. if I see it trending towards hotter than I can hold, Id invest in an OT gauge

Wed Jan 19, 2011 3:19 pm

Actually my pressure gauge has been a lot more useful to me in monitoring overal engine temps. The oil temp gauge is beneficial at slow speed around town but on the highway ambient highway air flushing the exposed portion of the sender really throws off the reading. All of the various ways and locations for an OT sensor all have their problems and mainly they are reading the temps of the enviornment and what they are mounted to and less of any actual oil temp. The pressure gauge accurately reads the lower viscosity from higher oil temp. And also engine clearances from thermal expansion. And it's pretty quick giving a real time indicator. The oil is flushing heat out of the high temp area of the heads in the rocker boxes. So oil viscosity is a good fairly quick indication of head temps along with general health. To learn how to trend is a pretty easy thing to do by getting familiar with pressure readings at various road speeds and how it varies with changing oil temp. During high ambient temp and hard driving where it starts getting to be a concern the press gauge is kind of like a back seat driver. "Slow down and take it easy".

Wed Jan 19, 2011 3:56 pm

Wow, so many differing opinions on this issue. Bottom line is all that I want to do is treat my 70k rebuild engine with care and tenderness so that I can drive it until I rebuild next year. Of particular concern is going up the mountain passes I go up going camping. Still seems like my best bet is to utilize the oil pressure, and for another $30 bucks, the Berg dipstick, and keep my eyes on the red flickering light. Thanks.

Wed Jan 19, 2011 4:01 pm

Lionhart94010 wrote: I would say both, but if you can only get one I would get the OT as when your heads get hot they heat the oil fast and you should be able to see the trend as said by “Desertbusman”

Until I installed my (5) CHT sensors I had no idea how hard I was pushing my camper, I’m sure if I had a OT connected I would have suspected it…

Just an FYI, the CHT I installed showed how fast a cylinder head temp can change, just by lifting off the gas a little and changing the speed by 2-5 MPH the heads would go from close to 500F to the 420’s (still way too hot)

RPM Not connected CHT Cyl #1 off by 32 degrees

Installing my CHT was an eye opening experience ;0)

Doing 60-65MPH with a fully loaded Camper, in the 480’s head temps, the Berg oil temp sensor would start to flicker… I was running synthetic oil, Until I installed the (5) CHT I had no idea that my engine was running this hot before the Burg temp sensor was bilking

516F sensor JB welded in head a bit closer to exhaust Port next to spark plug on #3
:0(

If those temps are real you either have a air flow issue, timing issue or need to sniff the mixture as it may be too close to 14.6 all the time. That high a temperature will cause failure unless those temps were taken on a day when it was 110F outside in which case 50 - 55 might be more appropriate.

Wed Jan 19, 2011 4:24 pm

Daddy68 wrote: Still seems like my best bet is to utilize the oil pressure, and for another $30 bucks, the Berg dipstick, and keep my eyes on the red flickering light. Thanks.
That sounds like an excellent choice. The bus guy in Bisbee had temp concerns and the Berg goodie let him know where his temps really were. Seems like some of his driving was right at the Berg number so it would go on and off depending on his driving and the terrain.