Author Topic: Overheating problem..... (Read 6307 times)

n_tensetuning · « **on:** May 30, 2004, 09:01:52 am »

it seems i have an overheating problem with the 1.6td in my 81 pickup.

i have replaced the radiator, tested the t-stat(in boiling water), flushed the entire cooling system 2 times..... i have even put the side coolant flange that was on the original 1.6 diesel(with the 2 sensors) and put it on the 1.6td and nothing
The radiator fan switch, and t-stat are low temp (from Techtonics)

now, the radiator fan does kick on, but i noticed that from a cold start the motor just warms up too much/too quickly.

yesterday, I set up a catch can/oil breather and now the valve cover is breathing through it.... i noticed a slight drop in temp....

i'm beginning to think something is up with the turbo.... maybe the wastegate is stuck? or the turbo is overspinning? I have done no boost mods and am seeing 10psi.

I really don't believe the motor should get this hot this quickly. I mean just after a couple mins of running... you can't touch the valve cover, or upper radiator hose.... never mind the turbo compressor housing

anyone know what else to check? maybe the oil feed line or oil return line? the oil return line does look a little kinked

anyone know how to check the turbo wastegate?

david

VWRacer · « **Reply #1 on:** May 30, 2004, 09:28:51 am »

If you are seeing 10 psi boost then it seems to me that the wastegate must be working.

There is an old racing technique used to control water temp that you may wish to try. Replace the thermostat with a piece of aluminum about 1/8" thick that has a hole in the center of about 1/2" diameter. The disk acts as a restrictor yet water can flow continuously (remember the hole...). If the engine warms up normally or doesn't get quite up to normal temp, then the thermostat is at fault. Or you can even delete the thermostat entirely, in which case the engine should be very slow to get anywhere close to normal operating temp. In fact, it may stay cold all the time, but in any case, this points to a bad thermostat. Replace it, irrespective of how well it performed in boiling water.

If the engine gets right up to hot temp even without a thermostat, I would suspect a cracked head. I have seen this many times with otherwise good running engines...the hot cylinder gases get into the water and heat it up really quickly. If this is the case it is bad news, and your best bet is to replace the head.

Pressurizing the water can be tested with an appropriate "radiator cap tool", essentially a solid radiator cap (no pressure relief valve) with a hose which is run to a boost gauge. You simply hook it and rev the engine to mid-RPMs. If cylinder gas is getting into the water jacket it will show up immediately as an increase in the pressure of the air over the water in the radiator.

Good luck! Stan

Edit: I have also seen cracked blocks cause this same problem, but only on V8's.

n_tensetuning · « **Reply #2 on:** May 30, 2004, 06:07:12 pm »

i just finished taking out the t-stat and watched the motor closely... it took a longer time to get hot.... but after a run around the block and on the highway.... the temp gauge climbed once again to nearly 1-2bars before the red.
When I pulled in.... same old thing..... upper radiator hose seems fully pressurized, and extremely hot..... valve cover same thing.... really hot

i also noticed while cruising at 65mph, etc... i'm running 5psi.... it almost seems that i have boost as soon as i touch the gas pedal :?:

i also noticed that the oil pressure on a cold start is near 75psi.... but as the motor gets really hot or after a run, and it's at idle it drops to around 15psi..... is this normal? because it is a diesel? no vaccum?

looks like everything is pointing to a cracked head :evil: i did do a headgasket and new bolts, when i replaced the timing belt.... i just don't get it.... the motor had run great in a 85 turbo diesel jetta

maybe i should try a tdi all metal headgasket? anyone know if this fits on the 1.6td? do they have 2 or 3 notch all metal tdi headgaskets?

david

n_tensetuning · « **Reply #3 on:** May 30, 2004, 11:22:35 pm »

now here's so weird shizzle.... just took the truck out again.... this time at night.... and the temp outside in the 50's....
drove a good 15miles.... the temp gauge stayed nice and cold while driving at 55mph (seeing around 2-5psi for boost)
anyways, decided to give it more gas.... around 8-10 psi as i got off the highway... and saw the temp go right to the middle.
I let the car sit for a minute or 2 when i parked, and saw the temp gauge pass the middle and back to 2 bars before the read :? then i heard the fan kick on....

i'm suspecting the fan is not turning on when it should be (at the halfway temp mark)

i mean, i'm driving around now with the T-stat removed, and I can definately see that the motor takes longer to heat up..... This should rule out the head being cracked, right? :?:

what baffles me aside from this is how much boost the turbo gives at 55mph in 5th gear (2-5psi).... at 65mph in 5th (8-10psi) and it stays at 10psi throughout 65mph+++

could the turbo be overspinning? i have to intercool the motor and see what a difference it will make

david

DieselsRcool · « **Reply #4 on:** May 30, 2004, 11:36:36 pm »

Check your engine to body ground.

I had a similar problem with my Samurai. I figured it out after noticing that the engine ran cooler with the headlights on :shock:

Dr. Diesel · « **Reply #5 on:** May 30, 2004, 11:50:39 pm »

bad grounds do cause all sorts of unexpected electrical gremlins.

Some of what you're describing doesn't really seem all that abnormal to me. An engine at running temperature will be too hot to touch, even on the valve cover. 4-8 psi is fairly normal for steady highway speeds. In fifth gear, at around 3000 rpm, boost will build from this range to 10 very quickly.
The oil pressure is a strange one. 15 psi is too low. Are you using 5 or 10w30? If yes, it's too thin. Min 10w40, or preferably 15w40. I'm not sure that a diesel's low vacuum has anything to do with oil pressure.
The TDI head gasket is overkill, even if it does fit. I don't think it would anyway. The IDI 1.9L does, though the bore size is different.
Sometimes it can be tricky to get all the air out of the cooling system. An air pocket can cause temp problems.

Do indeed check out the electrical system, but perhaps you're worrying about most of this stuff for nothing?

cheng · « **Reply #6 on:** May 31, 2004, 11:59:08 am »

ok heres what happened to me:

I replaced the radiator on my rabbit.
what I didnt notice at the time was that there was no water coming out of the return hose from the top of the radiator.

somehow (by accident) I got all of the air bled out of the system. ( still not knowing that the steady stream of water accross the topof the top of the filler neck is important).

I drove this way for months untill enough air worked its way into the system that it started to overheat! I removed the cap and it looks full.

anyway after a new head :evil: I checked the rad and realized that Modine never drilled out the return hole on the plastic tank.

they say education is expensive but so is ignorance :oops:

ken

dieseltech · « **Reply #7 on:** May 31, 2004, 02:23:48 pm »

dont trust the temp guage in the dash!!
i have had ones read in the red and the engine only be 195-200

the whole cooling system only holds 2 gallons of water. so it wont take a long time to get hot.
usualy after 2 min mine is up to running temp. i have heat on a -10 day in the winter before i leave my driveway.

the boost seems normal.

15w-40 oil in a td always.

n_tensetuning · « **Reply #8 on:** May 31, 2004, 05:54:22 pm »

i drove the truck again today.... and i always use the tripometer to see how many miles i get with a full tank..... i was looking at the fuel gauge and around 300miles, etc... i should already be at half a tank....

i wonder if my gauges on the cluster are out of whack.....

looks like i'll be adding a coolant temp gauge soon as well.....

dieseltech · « **Reply #9 on:** May 31, 2004, 07:15:20 pm »

there is a replacable voltage regulater in the back of the guage cluster.
it often times goes bad.
this will cause the gauges to read all kinds of nonsence.
i think radioshack can get this voltage regulator, its about $6 if not i know the dealer got them for me once.
this has almost always fixed the problems with oil lights coming on and low reading guages.
good luck

Otis2 · « **Reply #10 on:** May 31, 2004, 08:55:30 pm »

Before you swap the voltage stabilizer, you can test to see if the gauges respond properly with a decade resistance box (or, if you're cheap and don't have a decade box handy, then solder several resistors together to come up with the right numbers - you need four different resistance values: 35, 210, 340 and 30 ohms). This saves you from buying the "VW 1301" tool.

On my '85 vanagon, the wire from the tank sender to the gauge is purple and black. Disconnect it at a connecter under the dash, ground the decade box to the frame, put the "hot" wire from the decade box to the gauge side of the purple/black wire connector. Turn the ignition on. If you input 35 ohms to the gauge from the decade box, you should see a full tank, and if you input 210 ohms you'll get an empty tank.

For the coolant gauge, do the same with the coolant gauge wire (I can't remember now... yellow & red?) at a connector. Input 340 ohms to get the needle at the white "transition zone" of a cold engine, and 30 ohms to pin the needle hot and make the LED flash.

If the gauges don't respond to the resistance inputs, then either you have a bad gauge, or bad voltage stabilizer. If the gauges do what you expect, then you have a bad sender.

If the gauges don't respond, then next step is to test the voltage stabilizer on the back of the flexible circuit board with a multimeter. It should pass between 9.5 and 10.5 volts to the instruments when the ignition is on. If it doesn't, then there's your problem. If it does, then it has to be the gauge (or, in my case, broken copper connections in my rotten blue plastic circuit board, which I'm grateful to have found before wasting money on new gauges).

Note that the resistance values I suggest here are only approximate to the VW 1301 tool's values, and are not perfect. I got them from a vanagon guru, and they worked for my gauges, including the 1988 Jetta tach/fuel/coolant gauges that are in there now. So they should work with other factory VW / VDO fuel and coolant gauges from the 1980s (1990s?).

(There, now I've written something useful, instead of just asking for help here all the time!)