Overheating - No Thermostat?

[fiasco]

I'm having a problem with overheating. This issue is new this summer, and while it has been hot, it's no hotter than it was last year, and I did not have this problem then.

The Problem
The short story is that the engine overheats if I stop moving. If I stay at highway speed, it stays at about 200 (just a little right of straight-up on the dashboard gauge). If I have to stop and go (traffic or stop lights), it'll inch up toward the red. If I have to sit for more than about 4 or 5 minutes, I'll get into the red. Once I start moving again, it goes back down pretty quick.

What I've Done
I checked my radiator fan to be sure it is working, and it is. The fan switch has gone bad, but I jumped the connector wire, so the fan runs whenever the car is on. I flushed the cooling system using a "T" fitting on the heater hose at the top of the head,and refilled with 50/50. Burped the system using the open "T" fitting. Drove it a bit. Burped it again. No help. Same overheating symptoms as before.

So today I decided it was time to investigate whether I have a thermostat problem. I don't have an external thermostat (had one on my last Spider, so I knew what to look for), so I assumed I must have an internal thermostat in the head. Started taking things apart, and this is what I found.

No evidence in the radiator T, the fitting that goes on the head, or in the head itself that there is any thermostat whatsoever. The hose from the water pump goes straight to the lower radiator connection. It is a "ribbed" hose with wires inside (see pic below). I've never seen a radiator hose like this before - are the wires inside to keep it from collapsing? I ran a high volume of water through this hose when off the car and it did not seem to have any sort of blockage.

So I'm a little stumped at this point. Without a thermostat, shouldn't I be getting circulation of cooled water at all times? What are the downsides of not having a thermostat other than taking extra time to get up to operating temp in the morning (which doesn't seem to be a problem for me)? Would love to hear some thoughts, ideas, advice on what to do next.

[So Cal Mark]

Steve
those hoses are known as flex hoses and the wire is to allow it to bend without kinking. I'm surprised there isn't a thermostat anywhere. I'd suspect a plugged radiator if it runs at 200 while cruising with no t-stat.

[fiasco]

I'd suspect a plugged radiator if it runs at 200 while cruising with no t-stat.

I had that thought as well, but when I flushed the system it seemed like the water flowed through pretty easily, and when filled, it seemed to drain pretty easily out of the bottom of the radiator. I don't have enough experience though to know whether that would mean it's not-plugged, or if maybe it just means its not plugged enough to stop it from draining.

Either way - at this point I should probably pursue that as a possibility. Is there an easy way to diagnose whether it is plugged, and if so, what's my best approach to fix it (keeping in mind that I've already flushed it once with clean water)?

[So Cal Mark]

if it's restricted, rodding out is really the only way to get it clean. If you have an infrared thermometer it's pretty easy to check the radiator for restrictions

[BEEK]

one other idea, we learned in racing, running a cooling system without a thermostat can cause overheating, why you ask? the thermostat is a designed restrictor in the system, without this restriction the coolant can pass thru the radiator too quickly and never have the chance to be cooled. that is why we run restrictors in race engines not thermostats, as thermostats will fail, but restrictors wont..

[So Cal Mark]

I agree with the restrictor slowing down the flow, but if it's running hot at idle I doubt fast flow is the issue

[majicwrench]

If it runs hot sitting still, and OK on the road, radiator plugging is not the issue. Engine produces much more heat traveling down road, and if rad can get rid of that heat and keep temp under control it is likely OK. At idle much less heat produced. IF it can't get rid of heat at idle I would suspect something in engine, pump impeller (does that happen on fiats??) or air pockets. When it happens, fan is running (yes?) is rad fan blowing hot air or cool air?? That is a good way to tell if the hot coolant is getting to the radiator.
And as has been said, thermostat is there for a reason. But if tstat was out last summer and it worked fine, again that not likely issue.
Keith

[RRoller123]

On this car, is there a restrictor in the T like in the FI engine? Maybe it is in backwards?

[fiasco]

No restrictor in the T that I could tell.

I get the idea that the engine produces more heat while moving, but it also seems like the moving air would help cool the engine. The faster I'm going, the better cooling effect I get - so better at faster speed, even at similar RPM. But maybe I just have air-cooled on the brain due to the '69 Bug my son and I are working on.

Anyway - I'm going to see if Mark has a used rad that I can pick up, and between that and the one I have, I'm going to see if I can get one cleaned and confirmed un-clogged and see if that solves my problem.

-- se

[majicwrench]

If your current radiator can get rid of enough heat at hwy speed to keep engine cool, it can absolutely get rid of enough heat at idle. Replacing rad is not going to solve your problem, but tis your car.
Keith

[fiasco]

tis your car.

Ok Keith, I'll bite. What's wrong with my car?

-- se

[majicwrench]

I don't know what is wrong with your car. I do this for a living and I don't guess. But to repeat, a radiator that can get rid of enough heat at hwy speed can deal with the heat produced at idle. Again to repeat, when vehicle is overheating and rad fan is running, see if fan is blowing hot air. See if both hoses hot. Temp gun nice, they are pretty cheap nowdays. The fact that your car runs a tad hot at hwy speeds, and has already had Tstat removed, raises my eyebrows.
In my shop I would also check for exhaust gases in cooling system. NAPA has a kit with blue liquid, again cheap, that works well for this.
I'm not trying to be contrary or onery (sp?) just speaking my mind, and I can CERTAINLY be wrong too. I think I was wrong already once this year, so not likely twice.......
Keith

[fiasco]

Sorry Keith - I should've looked back at your previous post as well - I'll try to determine whether the radiator has hot/cool spots, and how hot the air is coming off the fan. Don't have a temp gun, but this is probably as good a reason as any to get one.

Of course I'll have to put it all back together, refill the coolant and drive it around some more to test. I'll post up some additional info once I know something new.

Thanks all!
-- se

[seabeelt]

Been down this road with our sons car. Best to get a thermal gun as mentioned before. Quick easy test for the rad is to stick a hose in the top from the motor inlet side and see what comes ou the bottom side. We have our own well water and pump so the water comes out of the hose real fast. Couldnt overflow the radiator, so backyard flow test looks OK. Used the thermal gun to get readings. constant temp at he top and you could watch as the temp moved across the bottom of the rad to the thermal switch. He had to burp his alot, and i mean alot to get all of the air out. By his temp gauge his runs at around 200, but its consistant. He just made the trip from Providence to Ithaca, NY, 360 mi, 7 hour trip with no problems, temp gauge around 200 the whole trip. We went along in my truck as luggage hauler and possible tow truck should he have a problem. It was a great confidence builder for him. In his car I suspect at this point, the thermal resistor for the temp gauge or the gauge itself. We have replaced everything else except the rad, and that looks good with the thermal gun. Long story short, test some more. I agree with Kieth, temp should not be rising with no thermostat at HWY speed. At idle, my temp creeps up due to lack of movement ( meaning the impeller doesnt turn fast enough (in my opinion)) to create enough flow without the fan constantly coming on. Again just me. I recommend getting a new fan thermal switch also, while you have things apart. AR has a lower temp one if you want the fan to come on sooner.

[jkn070458]

On my 78 the thermostat is part of the radiator hose(s). I had an overheat after initial start up. I'd check all of the above and then go after an air bubble that may be in the block. Fill the radiator as usual and then remove the heater hose that goes into the head and see if any air comes out on my car this is the highest part of the cooling system. I also back filled the block through the hose as well.