Coolent Flow Problem

[stomperz71]

Working on a "81 Caddy 1.6na Truck. This spring I get the truck out and it has a leaking injection pump. So I get the truck in my shop and start tearing it down. Got the pump off and sent it to Giles for a rebuild. While that was out being rebuilt I thought it would be a good time to replace some gaskets that were leaking, timing belt, tensioner, motor/trans mounts, water pump, t-stat, all water hoses and some other things. Doing all this because I bought the truck around two years ago and wasn't sure when all these item were replaced last. This truck is suposed to have 70,000 orginal miles, can't prove that though!

So know for my problem. I got everything back togeather, everything seemed to go back togeather real good. Ran a tank of fuel through the truck and I noticed that some times my temp gauge was reading a little high. Some times it would get up to temp and run at normal temp just fine. The times it did heat up I would get out and feel the upper and lower radiator hoses and the upper was real hot and the lower was cold. So I thought maybe head gasket, changed that and also got a new expantion tank and cap. Took out for a drive and same thing sometimes it would heat up just fine and others it would not. This would happen from a cold start up, if it would come up to normal temp after cold start it would be fine the whole time it was being driven. From cold start, and it would run on warm side, get out feel hoses upper hot lower cold, it would run like that for some time and while watching the temp gauge I would see it come down to normal temp as if the t-stat just opened, get out feel hoses upper hot lower hot. So now I think maybe bad t-stat, change it out and take it for a drive first four cold start ups it warmed up just fine both hoses hot. Thought it was fixed! Next time out it ran warm again, lower hose cold. Just took it out today and it warmed up just fine. Just seems like its either not moving the water(water pump)or the t-stat is not opening??

I've ran with the cap lose for awhile, drilled small hole in t-stat, filled the coolent through top radiator hose. Running out of ideas!! What would you do next? Which way does the water flow on these 1.6s, is the lower hose the return to radiator.


Sorry for the long post, just trying to explain what I have done best as posiable.

Oh, this truck ran great before I started any of this!

[R.O.R-2.0]

what brand of thermostat? if it didnt cost you 20 bucks or more, its probably your culprit.. the 6 collar budget stamped thermostats are garbage.. im running one in my rabbit, and it does the EXACT same thing.. some days it runs below the red on the gauge, other days it will not come up to operating temp..

[81 vw pu]

x2 on the thermostat, been chasing the same problem on my caddy for months.
Found a bad fan temp switch plug last week and thought that might be it.
Fan cycles great after fixing that but gauge still reads warm. Pulled the stat out sat. to have a look.
It had a gates 180f so for kicks I had a old oem 87c stat laying around. Bingo gauge only gets to the middle
now instead of near or at the red. No more aftermarket stats for me!!!

[R.O.R-2.0]

x2 on the thermostat, been chasing the same problem on my caddy for months.
Found a bad fan temp switch plug last week and thought that might be it.
Fan cycles great after fixing that but gauge still reads warm. Pulled the stat out sat. to have a look.
It had a gates 180f so for kicks I had a old oem 87c stat laying around. Bingo gauge only gets to the middle
now instead of near or at the red. No more aftermarket stats for me!!!

FWIW.. i have better luck with used OEM t-stats, than i do with brand new el-cheapo t-stats...

[stomperz71]

The two I have tried I got from Parts Place. The first one I tried said Germany on it, the second one(one I'm running now)they sent me did not have any markings on it but looked well made. I also got one from Napa and it looked pretty cheaply made, haven't tried it yet. I called my local dealer and they wanted something like $50 for a t-stat.

When it acks up and runs warm and lower hose is cold my fan will never start because the lower part of the radiator is cold. When its acking right normal temp I can let it idle all day and the fan will cycle on and off like it should.

I still have the t-stat I took out that was working fine maybe I'll try putting that back in.

[rabbitman]

How long are you letting it run to make your diagnosis?

Are you driving at highway speed or idling in your driveway?

[mystery3]

Does it ever get into the red? Does your fuel gauge ever act weird like read extra high?

[8v-of-fury]

Get that old thermo in to the kitchen.

Get on pot with a thermometer in it to 190f and another pot right beside it at 130f. Taking it out of one and in to the other over and over should make it open and close open and close open and close. if its working right like that, then you've got some otehr odd problem.

[stomperz71]

I've ran one whole tank through it, over 600 miles. I drive it 130 miles a day to and from work. It never gets in the red, when it runs warm its two marks away from the red. When it runs normal the needle is about straight up and down. After I pulled the first new t-stat out I took both new t-stats and the old one that was orignaly in it to the house and put them in hot water. I didn't do the two pans like you said but that would be a good idea. All the t-stats seemed to open at about the same time. Guess maybe I should just go to the VW dealer and get a OEM t-stat and see what happens.   

[8v-of-fury]

Well i mean if you really think about it.. that gauge only measures a minimal temperature span right? like 70-110c.. so whats that in F? So like 158-230f. The gauge in the middle runs at operating temperature.. or about 190f. So then for the gauge to read just a tad more in either direction is really only like 10-15 degrees.. and is more than likely nothing to worry about.

[stomperz71]

Yea I really didn't think it was getting to a point where it was getting to hot to drive or I would have left it sit. I just don't think something is quite right.

So which way is the flow of water? In the bottom hose out the top or in the top and out the bottom hose?

[R.O.R-2.0]

flows from the engine, out the top hose to the radiator, then it flows thru the rad, back thru the lower hose, then back to the engine..

i would bet you got a clogged radiator, a spun/spinning water pump hub, or a bad thermostat..

[stomperz71]

That's the way I thought the flow would be. Just could get through my head that the cooled water from going through the radiator would be going right into the t-stat. So you have the cooled water trying to open the the t-stat?? So by that the lower hose should always be cooler then the top hose?

In ran at normal temps all the time before I started replacing any parts. That's kinda why I rule out the radiator. The only to thing I replaced in the colling system is the t-stat and the water pump. I still want to say t-stat but hard to believe I would get two bads ones in a row! As far as the water pump, the last time I had the t-stat out I stuck my hand in the t-stat housing and held the water pump propeller and then with other hand tried to turn pulley that is mounted to water pump hub. Couldn't get it to spin on shaft so thinking the water pump is good. 

I'm just lost for what to try next. I get up to the VW dealer I'm going to get another t-stat and try that.

[R.O.R-2.0]

That's the way I thought the flow would be. Just could get through my head that the cooled water from going through the radiator would be going right into the t-stat. So you have the cooled water trying to open the the t-stat?? So by that the lower hose should always be cooler then the top hose?

In ran at normal temps all the time before I started replacing any parts. That's kinda why I rule out the radiator. The only to thing I replaced in the colling system is the t-stat and the water pump. I still want to say t-stat but hard to believe I would get two bads ones in a row! As far as the water pump, the last time I had the t-stat out I stuck my hand in the t-stat housing and held the water pump propeller and then with other hand tried to turn pulley that is mounted to water pump hub. Couldn't get it to spin on shaft so thinking the water pump is good. 

I'm just lost for what to try next. I get up to the VW dealer I'm going to get another t-stat and try that.

6 bad ones in a row wouldnt surprise me.. i go to the VW dealer to get my thermostats.. its the ONLY part i dont cheap out on.. they are a SUPER IMPORTANT part, and they need to work right..

[8v-of-fury]

That's the way I thought the flow would be. Just could get through my head that the cooled water from going through the radiator would be going right into the t-stat. So you have the cooled water trying to open the the t-stat?? So by that the lower hose should always be cooler then the top hose?

There is a little hose that goes down from the front neck to the wp is what heats the thermo and gets it to open. The bottom rad hose will always be cold until the thermo opens.. and should usually be colder than the top hose.. unless you've got a clogged rad.