Overheating... I've tried nothing and I'm all out of IDEAS!

So, joking on the title but my car is overheating.

First thought was the thermostat so to test it I took it out of the car and threw it in a pot of boiling water. It pretty much immediately began to open once it hit the bottom of the pot. The water pump was replaced when I rebuilt the engine several months ago, not sure if those go bad if they sit for ~6 weeks. The radiator is original as far as I know. For the record, I did run the car with no thermostat. It took a LONG time to heat up as expected, but once I was moving it never overheated or went above the middle mark on the gauge. Driving around town with no thermostat did make it a little cold but never dipped very far into the blue.  

I'm at a bit of a loss, help?  

1978 Opel Ascona B 1.2S

Well first, I wouldn't throw the tstat in an already boiling pot. If it's a 160° or 180°F you should watch the water temperature as it's heating up past the temperature in question.

Original radiator from 1978? I'd be taking that and having it boiled out. I went round and round with an overheating issue on my 1990 Acura Legend. New fans, new thermostat, flushed the coolant, and it still kept overheating. Sent the original 20 year old radiator out and it was all full and plugged up. Never had a bit of trouble afterwards.

The fact that you removed the thermostat and "cured" the overheating seems to point at the culprit IMHO.

Cleaning out the radiator is probably a good idea, too.

You rebuilt the motor a few months back.  I assume you just got it back together and this the first time you've run it since the rebuild?  The engine could still be tight from the rebuild and it will get better as it loosens up a bit.  However, it might be a good idea to pull the plugs and turn the motor by hand to see how hard it is to turn.  If it's really difficult, something was done wrong during the rebuild.  Could also be blocked water jackets if the block wasn't cleaned well.  Did you work on the fuel/ignition after rebuilding or just bolt it all back together?  If it's running too lean or if the timing is off, that could cause overheating also.  When does it overheat and how bad?  Is it within minutes of starting it up?  After driving around for a while?  Only at idle?  Did you burp the cooling system to make sure there's no air bubbles in it?

-Rob

You need a bigger fan

Under what circumstances does it overheat?

BTW, just because a thermostat opens in hot water doesn't mean it opened fully. IME a thermostat can look like it's working perfectly fine, but actually open too early and then not open fully. Result - car overheats.

new rad(or rebuild old one) and thermostat...  don't screw around with unknown parts and a "new" engine

Also, check the hoses.  I had one in a Datsun that was collapsing.

Check the timing, definitely. The old Le Mans used to run chronically warm. After lots of cooling system fiddling, we happened to time it as regular maintenance. It was way off, even though it ran fine. With the timing on the mark, it ran perfectly cool. 

RossD: I assume its the 180* one since the thing says 82C ~ 180F. I didn't know that put it in as it goes up thing, I'll try it another day.

NickD: Possible to boil out at home?   

Boxhead: I wasn't sure at the time since the thermostat 'passed' the test  

rob_lewis: It's not the first time its been run and the timing is set as it's suppose to be per the haynes manual. Mark to mark with the light. IIRC I did my best with the eBay vaccum gauge to set the carb but that was months ago. Long story short, Germans are a PITA with their inspections and under the SOFA agreement it's even harder to get more inspections after the time slip is up. On the first try the motor went, so I rebuilt it. The second I failed for some minor stuff and wasn't allowed to move the car for a simple drop of oil. Car didn't overheat and ran fine then, until after I was forced to park it did problems arise. Standby for a few months trying to find and get the paperwork in order because my current Chain of Command sucks at getting the things the Jr. E's need in a reasonable amount of time. Fast forward, I get 48hrs to try and pass again - pull 18+hr days and win. I passed. Don't remember what time/day it exactly overheated, but it wasn't more than a week (I passed around the 20th this month). Eeeerm, I think that's the history on the car. I don't know if thats what you wanted, but I hope it helps!

APEowner: pretty much a problem at 100k/~60mph but starts to be an issue at ~80k/~50mph. I threw the thermostat back in today  

Caffeine: I don't like to shotgun parts, but if I were I'd add water pump to the list

Caffine: those are new and sturdy/stiff/whatever, even when hot  

Duke: Interesting, I'm gonna have to fiddle with it.  

Thanks for all the suggestions guys! Appreciate it!

So, it's OK at idle and around town but heats up running down the road?  That's probably the radiator.  It could also be an airflow issue but based on a wild guess and looking at pictures of Opel Asconas on the internet I don't think that's likely.

what'll honestly likely happen is testing the thermostat again and a basic maintenance of timing/carb adjustments. forgot to mention, today was the only day from the past ~10 days that it overheated idling.

Cooling system cleaner and flush. 

Are you going by an actual temp gage or is it just colors on a dial?

In reply to dean1484 :

The one in the car 

TurboFocus said:

In reply to dean1484 :

The one in the car 

And what is in the car? 

The reason I ask is gages go bad as do sending units. I would be wanting to know that they are working properly. 

Yeah, t-stat could be suspect. I don't normally test them. If I pull it out, it's just $12 more bucks to put a new ine in. The drive to the parts store takes as long as it takes to boil the water. 

That being said, get the radiator serviced. 

Either coolant flow or air flow.

If it's a sane overheating at speed, it'll be air flow or coolant flow, but a restriction somewhere nonetheless.

If it's furious overheating at speed, it could also be a leaking head gasket.  If combustion gasses are getting into the coolant, ain't NO cooling system in the world that can cool that down.

The fact that you rebuilt it, would lead me down that path. There are dyes you can put in the coolant to tell if it's leaking, or run it with the cap off and coolant flowing through the thermostat - if there's a bagillion tiny bubbles frothing through the system, go order a head gasket. And maybe check the head and block for flat.

The pot you put the stat in is much hotter than the water.  Suspend the stat so it doesn't touch the pot.  That is much more accurate.  

Looks like you need a new thermostat first of all.

so, got a new thermostat... installed it and it overheated just sitting there again. there is flow thru the radiator and some small bubbles, not a gajillion of them though. new clue, liquid out the tail pipe... tastes sweet. next step is pulling the plugs to see if they're steam cleaned and a couple of other tests (compression/vacuum) just to see the overall health. will update

when i rebuilt the motor i had the machine shop deck the head and block, put in a new head gasket while i was at it. torqued it all to spec, what gives? all it did was sit for a few months...

REALLY don't wanna replace that. Won't be that hard with this car but still.