Diagnosing Overheating

[whisker]

81 Dasher 1.6.

I've gotten my car to the point I can drive it, and figured out how to get the aftermarket temp gauge to move. I have it connected to the lead off the back of the head where there are two wires, one on each side of a coolant hose flange.

If this gauge is correct, I'm running at about 235 degrees, hotter when up a hill.

How do I know if this gauge is right? I don't want to blow this motor.

If I remove the cap- the coolant isn't boiling over.

[82vdub]

From your comments, I believe you've installed the temp sensor in the flange on the head on the drivers side of the engine. This is the outlet that sends hot water to the heater core. The 235 temp you measured may be correct for that location as it's taking the hotest water and using that for the heater core.

Did you remove one of those two sensors, or did you try rigging up your temp gauge to these sensors? If you didn't use a sensor that matches your gauge, you will get weird readings.

I believe the more appropriate location for the temp gauge (not idiot light) is in the upper hose going to the radiator. This hose flows water (low rate) to the overflow jug, and then moves more water when the tstat opens.

Well, now that I think about it, I thought I knew a good answer when I started this message, but it really brings up a good question on where's the correct position to meausure coolant temp with a gauge? These VW's use a bypass hose system so water isn't really flowing to the radiator until the tstat opens, but if your cars overheating cuz the tstat isn't open, will the temp gauge in the upper hose really reflect an overtemp temperature reading that's accurate? Or would the better position for a temp gauge be in the bypass hose that goes from the head to the water pump or even yet somewhere else?

[sgnimj96]

In a 1.6 diesel car that was not driven for a while I had a sticking thermostat overheat it (going up a big hill), check that if you haven't already. The easiest way is to just get a new thermostat.

[Fatmobile]

A candy thermometer in the resevoir can help you see if the gauge is close.

[Quantum-man]

Are you running a strong solution of antifreeze? That may account for your not boiling over
When going up these hills are you pushing the car to the limit, or is there more in reserve? Smoking much?

Here's an interesting link:

https://uk.answers.yahoo.com/question/i ... 826AAm9T9O

[whisker]

Replaced the thermostat and fan switch and it seems to be holding good temp. also realized the temp gauge wire was a different color than the manual specified- so now i have two temp gauges.
Thanks.

[82vdub]

also realized the temp gauge wire was a different color than the manual specified- so now i have two temp gauges.

Not sure what you're saying here.

[vwtyp133]

Re. the diesel Dasher, one of the two senders back there is for the gauge, the other is for the thermo control of the glow plugs' circuit. If the engine is already hot enough the glow plugs (supposedly) won't turn on at start-up.

The Dashers, having the engines mounted in the chassis longitudinally, don't have the 'front & center' location available for a wider radiator as seen in the early Rabbit/Jetta/Scirocco/Caddy, so Dasher radiators are taller but narrow & stuffed off by the driver's side corner (not the best for airflow ). That along with weighing a few hundred pounds more, earns the Dashers a reputation for tending to run somewhat hotter than R/J/S/C models powered by the same engines.

In West Coast summers the cooling systems of my Dashers often seemed marginal at best, even when using a dash-mounted switch to manually activate the radiator fan a few minutes prior to starting up a long grade. The problems went away for my '80 wagon when I chemically cleaned out/neutralized/flushed the entire system, installed a new water pump (with all casting flash removed from the pump mounting flange), used the minimum amount of anti-freeze to realistically prevent freezing in my areas of travel (never needed the 34 degrees below zero Fahrenheit protection a 50/50 solution claims!), added a bottle of Redline's Water Wetter, then topped off with distilled water. Oh, it also got a new and tested German thermostat & thermo fan switch, both rated IIRC around 195 degrees F.

After that service, except in slow in-town traffic snarls, the fan never came on, even when slowly pulling a 2,400 Lb trailer up & over mountain passes on a 3,700 mile trip in the summer. Now maybe it would have been a better test if I'd hooked up the factory A/C before the trip, but I just ran out of prep time. That's for future challenges!

Honestly it took doing it all. Ethylene glycol has only about half the heat-transfer ability of pure water (propylene glycol has even less than e.g.), so using a higher percent of anti-freeze than needed in the coolant mix is not only wasteful, it defeats the cooling efforts, both in the total heat dissipated to the air, and also the time it takes to cool down the heat of the engine. Water Wetter adds great corrosion control, although its primary function (I'm told) is to reduce surface tension to allow even greater heat dissipation... from the hot engine to the cooling solution, and from the coolant to the metal of the radiator.

A very happy day when it all finally came together & worked flawlessly. My oil temperature gauge confirmed what the somewhat nebulous oem water temp gauge was saying... life was good!

Sorry for the long-winded tome; hope that helps resolve some issues.

[sgnimj96]

I had a 80' Dasher wagon. Sometimes I would use the cabin heater with the fan on high as an "auxiliary radiator" in an emergency. Ended up getting the old brass radiator cut open and cleaned out.

[damac]

I don't recall ever getting such a hot reading on any of my engines at any point with a point and shoot tool?

I guess proper hookup and type of gage might play tricks on you.

I use auber gages on the cars I daily drive. I have the sender on the front port of the head that takes big hose to radiator top.

Right now I am driving my 79 rabbit 1.6td,no ac. Stock thermostat/fan sensor.

I don't hit 200. My fan turns on before that happens during all my normal driving. I see temps slightly rise on hills and with more boost and also sitting still in traffic but again the fan doesn't let it happen.

[vwtyp133]

Oh yeah, one more thing... especially on the Dashers, you're generally in a no-win battle against eventual overheating situations IF you don't have the factory - or replacement - air shields/directors/deflectors/flaps/seals/whatever-you-call-them in place around the radiator. That tall skinny-ass radiator, by itself, allows too much air to flow around it, bypassing the radiator core & the VAG plan to keep the thing in a liveable temperature range.

Re. the factory's goofy cardboard oem stuff, I don't know if it was ever available @ the VW stealership's parts dept (didn't even get my 1st Dasher until 1988; definitely NLA by then!). Solved the '79 sedan's missing air shields (/whatever) problem by cutting out/taping up cardboard patterns, then duplicating those by bending up UN-tempered aluminum sheet (about 0.040" thick IIRC). Between oem bolt locations (through rubber insulators) & aluminum pop-rivets, it wasn't that bad of a job... at least functionally. Protecting the upper radiator edge is a thick-wall 1/4" vacuum hose, split down one side & glued into place on the shield. I actually like the little diesel's rattle, but I hate the way it tries to get everything else on the car to join in that noisy vibrational chorus while drivin' down the road or even idling in the driveway! Insulation is your friend in mounting anything on the early VAG diesel vehicles!

Crap... another issue. CAN/U.S. Dashers/Audi Foxes have a pair of rubber flap shields around the Left side idler arm, to 1) keep mud/spray/splash out of the engine compartment, and 2) to direct the engine compartment air to flow past the hot exhaust down pipe on its way out past the Right side idler arm. Have heard that some Dashers had rubber anti-splash shields on both sides in hopes of keeping things extra clean; that's not the way to go & the already-thermally-tortured starter solenoid will tell you so fairly shortly, accompanied by general overheating of both the engine and passenger compartments. The dimples are there on the Right inner fender panel, ready to be drilled for mounting a 'spare' set of sealing flaps there also... resist the temptation. Don't ask!

Dashers are somewhat unique here in N.Amer, but (having had several of each) IMO are a step up in comfort, space & utility over the slightly lighter Rabbits/Jettas, of the same time period, as economical longer-distance cruisers, and the diesels are usually within a couple of MPG of the diesel Rabbits' highway fuel economy. Around town, the Rabbits will always win on MPG and also acceleration (no bragging about either as stockers!).

[whisker]

Oh yeah, one more thing... especially on the Dashers, you're generally in a no-win battle against eventual overheating situations IF you don't have the factory - or replacement - air shields/directors/deflectors/flaps/seals/whatever-you-call-them in place around the radiator. That tall skinny-ass radiator, by itself, allows too much air to flow around it, bypassing the radiator core & the VAG plan to keep the thing in a liveable temperature range.

Re. the factory's goofy cardboard oem stuff, I don't know if it was ever available @ the VW stealership's parts dept (didn't even get my 1st Dasher until 1988; definitely NLA by then!). Solved the '79 sedan's missing air shields (/whatever) problem by cutting out/taping up cardboard patterns, then duplicating those by bending up UN-tempered aluminum sheet (about 0.040" thick IIRC). Between oem bolt locations (through rubber insulators) & aluminum pop-rivets, it wasn't that bad of a job... at least functionally. Protecting the upper radiator edge is a thick-wall 1/4" vacuum hose, split down one side & glued into place on the shield. I actually like the little diesel's rattle, but I hate the way it tries to get everything else on the car to join in that noisy vibrational chorus while drivin' down the road or even idling in the driveway! Insulation is your friend in mounting anything on the early VAG diesel vehicles!

Crap... another issue. CAN/U.S. Dashers/Audi Foxes have a pair of rubber flap shields around the Left side idler arm, to 1) keep mud/spray/splash out of the engine compartment, and 2) to direct the engine compartment air to flow past the hot exhaust down pipe on its way out past the Right side idler arm. Have heard that some Dashers had rubber anti-splash shields on both sides in hopes of keeping things extra clean; that's not the way to go & the already-thermally-tortured starter solenoid will tell you so fairly shortly, accompanied by general overheating of both the engine and passenger compartments. The dimples are there on the Right inner fender panel, ready to be drilled for mounting a 'spare' set of sealing flaps there also... resist the temptation. Don't ask!

Dashers are somewhat unique here in N.Amer, but (having had several of each) IMO are a step up in comfort, space & utility over the slightly lighter Rabbits/Jettas, of the same time period, as economical longer-distance cruisers, and the diesels are usually within a couple of MPG of the diesel Rabbits' highway fuel economy. Around town, the Rabbits will always win on MPG and also acceleration (no bragging about either as stockers!).

Thanks for the very insightful info- not alot of folks have this knowledge on the dashers.

The guy I bought it from had to rebore the motor I think twice due to a vertical score on cylinder#1 (on the dashers, the one closest to the grill/headlights). The score was both times on the air intake side of the cylinder... (which is strange as that should be the most oiled part of the cylinder as they're mounted at an angle, favoring oil on that side, maybe...)

His best theory was all the air directing shields/baffles that mount on the underside of the engine compartment. He gave me all that stuff to mount up- any opinion on this theory?

Also- I may be missing some of those radiator baffles. Any pictures/diagrams on how to recreate those?

[vwtyp133]

Cylinder scoring @ same place? Sounds more like he had a problem with the rings to me, maybe inadequate tension or a burr on the end of a ring (assuming the ring gaps were spaced out @ 120 degrees, not 'lined up all purty'!).

IIRC the Bentley manual for the Dasher has some good illustrations showing the oem air deflectors; they were at the top & bottom, and on both sides of the radiator. On the non-A/C cars (never had one myself), they may have had a deflector panel behind the grille's right side also. Bottom line is that you want to force as much air as possible to flow through the radiator, rather than around it. A real lower air dam should also help quite a bit in that effort, as well as in reducing underbody air turbulence. Having less aerodynamic drag in highway cruising mode means less work for the engine to maintain a given road speed. I'd keep those under-engine panels; they help in that regard as well.

Been told that the surface area of the forward radiator core layer is more important than the total volume of a radiator's core. IDK; sounds somewhat plausible, but at some point I'm still going to have a thicker core(3- or 4-layers) built into a radiator shell for one of my Dasher diesels to test the difference. Another help could probably come from running a later model VW's 2-speed electric fan motor, as both my current Dashers ('80 & '81) have factory A/C. Maybe overkill, but it can't hurt, especially when pulling a trailer in the summer.

[whisker]

Cylinder scoring @ same place? Sounds more like he had a problem with the rings to me, maybe inadequate tension or a burr on the end of a ring (assuming the ring gaps were spaced out @ 120 degrees, not 'lined up all purty'!).

IIRC the Bentley manual for the Dasher has some good illustrations showing the oem air deflectors; they were at the top & bottom, and on both sides of the radiator. On the non-A/C cars (never had one myself), they may have had a deflector panel behind the grille's right side also. Bottom line is that you want to force as much air as possible to flow through the radiator, rather than around it. A real lower air dam should also help quite a bit in that effort, as well as in reducing underbody air turbulence. Having less aerodynamic drag in highway cruising mode means less work for the engine to maintain a given road speed. I'd keep those under-engine panels; they help in that regard as well.

Been told that the surface area of the forward radiator core layer is more important than the total volume of a radiator's core. IDK; sounds somewhat plausible, but at some point I'm still going to have a thicker core(3- or 4-layers) built into a radiator shell for one of my Dasher diesels to test the difference. Another help could probably come from running a later model VW's 2-speed electric fan motor, as both my current Dashers ('80 & '81) have factory A/C. Maybe overkill, but it can't hurt, especially when pulling a trailer in the summer.

Thanks- I have a copy of that manual i'll see if I can recreate those deflectors.

Have you ever changed an oil pan gasket on a dasher? Seems like the rear bolts are inaccessible due to the transmission. Any way I can do it without disconnecting the trans?

[82vdub]

Any way I can do it without disconnecting the trans?

1/4" swivel socket and an extension will work.