Author Topic: Coolent System Mystery (Read 6261 times)

55mpg06 · « **on:** March 27, 2007, 11:59:40 pm »

Hi guys. I don’t think this is a duplicate post so I hope I’ve put this in the right place. Sorry in advance for the long post (suggestions welcome).

My 1986 1.6L N/A Jetta is having a really strange problem for the past couple of years.

Problem: No matter how hard I’ve tried I always have a problem with no heat (sporadically) in the winter time and it seems to spray antifreeze out of the rad cap whenever it feels like it most of the time it all works fine for a week or two after I change the thermostat and antifreeze.

History: 2 years ago I had problems with my head gaskets blowing repeatedly. One it started to blow on a road trip so I reluctantly put two bottles of stop leak stuff found at a gas station and drove for 3 days to get home. Sent head to Bow-Wow to be checked out. It was highly worn but rebuildable. They completely rebuilt it (just kept head).
Installed rebuilt head with new injectors, water pump, thermostat, rad hoses, oil pressure sensors, and all new gaskets on top end. Also did all bottom end and tranny seals and new clutch while at it.

I was no longer blowing out antifreeze, instead my coolant reservoir cracked twice (replaced it three times). Got new rad cap and problem solved. During the winter found that heat output was sporadic and at times non existent with the temp gauge showing it not heating up.

Replaced thermostat again (oem specs). Problems solved for about a month, until again sporadic heat and reservoir venting antifreeze. Flushed system with rad flush. Helped for month then same problems. Note: no water in oil, no coolant or moisture (jar test) out of exhaust, and no bubbles in reservoir.

Repeated above less chemical flush twice during summer.

In fall rebuilt bottom end (it went). Block checked by a reputable machine shop in town and honed. Re-rung, new oil pump, all new bearings, all new seals and gaskets on bottom end and transmission (why not again since it was out). New thermostat (10oC cooler). Same problems.

Replaced thermostat with new OEM again. Worked for a week then same problems.

Read thread about blocked return line as possible problem. Checked and return line output sporadic and very weak unless hi rpm’s. Cleaned it out and again worked for a week.

Recently bought a rad flush adaptor that uses compressed air and a garden hose to blast the coolant system to the moon! :evil: Worked well and finally got out all (I think) the little black specs from the coolant system that were there ever-since I used the coolant sealant.
Now with warmer weather I don’t use the heater as much but if I have the heater on for a while the temperature gauge drops to the bottom again. The coolant still sprays out of the reservoir (especially with the heater turned off) and the coolant in reservoir seems very (like overly) hot. No bubbles in reservoir, no water in oil, and not moisture out the back end.

Result: Clueless. Friend recently mentioned remote chance of a faulty water pump. Is this possible? Any ideas? I have a pressure gauge to test the cooling system and it seems normal (not fluctuating like an exhaust leak).
:?

jtanguay · « **Reply #1 on:** March 28, 2007, 12:41:41 am »

but you had a new water pump installed??? I'm going through similar problems myself... my temps just keep climbing and climbing to alarming levels (my balls arent big enough to see the breaking point of my motor.. because i need this engine to last a little longer... maybe ill take it on the highway one day and see when it blows??)

i'm also considering my coolant pump as the culprit. Mainly because my car's temp is perfect at idle. fan kicks on too! if i drive super hard and the temps go high, i can let the car sit in my driveway and idle for about... 20-30 seconds, the temperature slowly drops to operating temp. (when the weather gets better I will check and see if the fan kicks on during this time...)

i suspect that my impelar is loose and spins at low idle speeds, but not highway speeds... very very frustrating problem indeed!

if you ask me, i would say that the temps are dropping because of a faulty thermostat. i've seen what faulty thermostats can do... my first diesel jetta was sort of a bad experience... i had to drive 120km/h on the highway to get a *little* heat on a really cold day. 100km/h i would freeze (hmmm probably not good for the motor!)

now with the new thermostat there is TOO much heat!!! :lol:

55mpg06 · « **Reply #2 on:** March 28, 2007, 12:55:37 am »

Yes I did have a new one installed when I did the head. However if it is possible for the impeller to come ocasionaly loose and not circulate the coolant properly or irradicaly, that could cause all sorts of problems I guess. Hmmm good thought, I'll try to take it apart tomorrow. As far as the thermostat goes I just don't know the possibility of 4 different ones from multiple places being faulty, but then again, for me I can see it happening :lol:.

jtanguay · « **Reply #3 on:** March 28, 2007, 11:09:10 pm »

Quote from: "55mpg06"

Yes I did have a new one installed when I did the head. However if it is possible for the impeller to come ocasionaly loose and not circulate the coolant properly or irradicaly, that could cause all sorts of problems I guess. Hmmm good thought, I'll try to take it apart tomorrow. As far as the thermostat goes I just don't know the possibility of 4 different ones from multiple places being faulty, but then again, for me I can see it happening :lol:.

test them in boiling water. dunk one in @ the opening temp and take it out... the t-stat should close fairly quickly.

clbanman · « **Reply #4 on:** March 29, 2007, 09:26:50 am »

The boiling water trick isn't fool-proof. I had a Civic with problems getting heat. I went through 6 Crappy Tire and various jobber thermostats ranging from 180 degree to 195 degree ratings, no difference. Finally broke down and bought the Honda part. They only sold a 160 degree thermostat for my car. Instant heat. I tested the 160 in the same pot with the 195 I replaced, and it opened first and further. No logical explanation, but at that point I didn't care.

jtanguay · « **Reply #5 on:** March 29, 2007, 10:41:03 am »

Quote from: "clbanman"

The boiling water trick isn't fool-proof. I had a Civic with problems getting heat. I went through 6 Crappy Tire and various jobber thermostats ranging from 180 degree to 195 degree ratings, no difference. Finally broke down and bought the Honda part. They only sold a 160 degree thermostat for my car. Instant heat. I tested the 160 in the same pot with the 195 I replaced, and it opened first and further. No logical explanation, but at that point I didn't care.

yea i would agree not to get a t-stat from c-tire or some other place... i went straight to VW to get my t-stat.. i payed about $30 for it, but it payed off in the winter as the gauge starts moving after a few minutes of driving!

55mpg06 · « **Reply #6 on:** April 01, 2007, 07:47:42 pm »

Hi guys, here is an update on the situation. I took off the water pump and again flushed the system. The water pump seemed OK, but I put in a new one that I had laying around anyway along with a new VW thermostat (I remembered to test it first as suggested). I put it all together and while I had good heat I still somehow lost coolant out of the expansion tank. Still no bubbles at all in the tank, no white smoke and not water in oil. The reservoir would mysteriously drain until it is empty if I let it.

I did notice, however that when I revved the car up with the rad cap off the volume of the return feed to the reservoir increased as it should; but when it became faster than a fast idle, the return coolant hit the other side of the cap opening and shot straight up out of the tank about 6 inches! :shock: In looking at the two other cars I work on, this didn’t seem normal. I wonder if the spray would force it’s way out of the new rad cap (the new blue one is physically a lot different than the old black ones) and maybe that’s why I would never actually see any spraying out, only the sticky wet evidence everywhere. I replaced it with a untested, but I think good, black rad cap and the problem’s seemed to go away. Do you guys think I might have stumbled upon a faulty reservoir with the return inlet angled up too much or do I have excess return line pressure for some reason eventhough I’ve been flushing it. It is a VW tank but was used. Thanks again for your help.

burn_your_money · « **Reply #7 on:** April 01, 2007, 08:22:05 pm »

You may have cracks in the head that is forcing too much pressure into the cooling system. You said you have a gauge right? Isn't there also a test to check for carbon (or other) in the coolant to see if the combustion gasses are getting into the coolant?

jtanguay · « **Reply #8 on:** April 01, 2007, 08:50:01 pm »

if i were you i'd just get an easy fix... people might cut me up for recommending this, but i dont care. how much is a new head & bolts & gasket & labour???

www.steelseal.com i would try their product out. it really seems to work!

Powjetta · « **Reply #9 on:** April 03, 2007, 08:49:15 pm »

You should have a small restrictor in that return line to the expansion tank that should keep the squirt to a smaller trickle. Have you replaced this line and do you know if you have the restriction? You can feel it in the line and I took my old one and put it in the new hose.