Overheating...AGAIN!

[pwilliam]

Hi All,

Need some help on this one! Story starts with a well running car, while on the highway I notice the temp starting to rise so I pulled in at a gas station and there was air in the system. My suspicion with the head gasket since I knew the thermostat, heater core, and the radiator were all in working order. So I my dad ordered the auto-ricambi hi performance head gasket(great by the way! thanks csaba!) and replaced it and snapped a headbolt in doing so...head was removed again and new bolts were put in, properly torqued. The gasket didnt look mashed from the first time I put it on so I didnt question reusing it. This didnt remedy the problem as hoped. Come to find out..at least one of the issues was the radiator cap. I noticed while filling the t I installed to help bleed the system, it would keep drinking and drinking coolant. That was because the cap was defective and let the coolant run into the overflow.

So I bought a new cap, 13 psi and the car eventually sucked coolant back in from the tank. When I would check the bleed t it was always full to the top but the car kept running hot. The fan would never kick on. Car would run around 190-195 driving slow or on the highway and this lasted for about 5 days before I hit some stop and go on my way into work after cruising on the highway. Temp got to around 240...still no fan. Pulled it into my parking space and coolant was spraying out of the water choke hose and then later, the hose that runs from the heater core to the heater pipe. Replaced that and the heater pipe for good measure (Dad has tons of spares...thanks Dad!) Tstat was replaced for good measure as well.

Started the car up, ran around 190 for a while until it eventually climbed to 235 or so and the water choke hose sprang a leak again. I've spent more time working on this car than driving it! I always wanted to gain mechanical experience..but this is getting to be excessive =)

My thoughts are that the system is building up to much pressure when the coolant heats and expands. The new radiator cap is not letting it expand into the expansion tank so it is looking for another way out-hence the leaks in the hoses. Tstat opens- the hose to the bottom of the radiator is certainly getting hot, but still no fan. Dad jumped the fan last night and it functions, but maybe the sensor is just bad? Dad also thinks the radiator might be blocked, but there was turbulence in the coolant when we ran it with the cap off. Going to take it to a garage and see if they can check if I have CO2 in the coolant system. A little glimmer on top of the coolant in the expansion tank but not enough to make me think oil is really getting into the coolant, probably just a little in there from when I changed the head gasket. Oil is not milky. Heater kicks on nice and hot, even when temp rose, so I dont think it really has air lock.

Any additional thoughts on the matter would be appreciated! This has been driving me crazy for almost two weeks now! Help save Seraphina!

[4uall]

This might help

http://wwwe.fiatspider.com/f08/viewtopi ... on#p126761

[pwilliam]

I wish I had an internal tstat, but sadly I do not -that'd be an easy fix. Thanks for the suggestion though.

[4uall]

I would flush the rad, take all hoses off and check for cracks etc, then assemble and follow burping instructions (in previous post) good luck with it, I know your pain

[azruss]

make sure the cap you bought has the 2-way valve in it. also make sure the thermostadt is oriented correctly

[pwilliam]

I'll be sure to check the cap tonight. Tstat is facing the correct way, good thought though. Thank you.

[4uall]

[majicwrench]

If it goes several days fine on road, then overheats stop and go, and fan is not coming on, obviously FAN NEEDS TO COME ON!!
If lower radiator is HOT (too hot to touch comfortably) and you can jump switch terminals and fan runs, that tells you that switch is bad.
Get the fan running. If the radiator was plugged, it would overheat on hwy (which creates lot of heat to get rid of) more so than stop and go.
Keith

[pwilliam]

Hmm, sounds like check rad cap, check for CO2, and replace fan sensor are the next steps here. Two things worth noting: 1) I thought an earlier switch was bad, I believe I popped it by heating it up too hot with a heat gun...it never worked again after it first wont on, via hitting it with the heat gun. Not sure if anyone can speak to the sensitivity of these little sensors. 2) On previous occasions, just testing the if the fan would eventually come on, it would - but only at about 230-240...way too hot. I am wondering if the last time this happened it caused the sensor to bust like I did with the heat gun. 3) Highway temp got up to 220 or so after fixing the leaking water choke hose, but I think 220 is too hot to be cruising on the highway at 55mph.

I am hesitant to think the radiator is blocked based on the coolant turbulence I saw, but I am not ready to discount that theory. Is there another way to see if the radiator is blocked without taking it to a shop and having them test it?

[majicwrench]

Your original post say "190-195 driving slow on hwy" or something like that. If Indeed it is running 220 on hwy, radiator could certainly be blocked, but it would be rare indeed to have a radiator so completely blocked that no hot water could get to the fan switch.
As you likely know, fan should come on about 200. Do you have a noncontact thermo gun?? You could check temp of radiator by sensor.
If you wish to check radiator, simply pinch upper hose, pull lower hose, stick garden hose in to rad cap opening. A full bore garden hose flow will not all go thru to bottom without overflowing, but you should see a substantial amount of water coming out lower hose.

[seabeelt]

I will add my two cents here as amplification. From the original post, coolant did have exhaust gas positive test results as performed by a reliable radiator shop. Head gasket was replaced, head installed without intake manifold and torqued. We then realized it was almost impossible to get the intake manifold back on. Soooo head comes back off and we reinstall the head - same gasket. Car ran fine a couple of days and then started overheating again. Head gasket was suspect because of having torqued it twice. Hence ordering the high performance gasket from Csaba. Multiple thermostats have been put in the pan on the stove and checked with an IR gun. We picked the one that opened first at or before 190 deg.

As a side note, the head gaskets have been put on by torquing in 5 lb increments to the final proper torque spec. We have two torque wrenches, one old style bar indicator type and one click style as a double check.

The fan sensor at the bottom of the radiator has been replaced, ( after checking the existing one with a heat gun - looking for the connectivity temp indication)

Last week after burping the system again on an incline in the drive, the fan cycled on three to four times as normal.

That was before this weeks latest escapades with the heater and carb hoses bursting.

Further as the car warms, the top two radiator hoses become hot as the should, but also feel very firm, almost rock solid before the thermostat opens.

IR gun indicates tha the top of the radiator is around 200 - 210, bottom near the thermal switch indicates between 150-160, which would not trip the therm switch to run the fan

The only things that have not been replaced at this point is the water pump (which seemed to splash coolant when turned manually with the thermostat out) and the radiator.

It should be mentiond the car is an automatic

Radiator seems to dump coolant pretty quickly if you pull the sensor or pull the bottom radiator hose and looks clean from the view down the radiator cap.

The need to dribble coolant/water into the high point of the system after every drive as if the car needs another burp, at the flush t is worrisome

Also should mention that we have looked at the timing set up. Spark was initially advanced beyond 10 deg BTDC, but corrected back to 10 deg. Idle speed was readjusted. Car now idles at around 850 rpm when in drive and timing is correct.

When we had the head off- sorry we didn't take pictures- the head and cylinder were all very very clean - very light whitish tan on the valves, head and piston tops

[TX82FIAT]

Did the car sit for a while before getting it back on the road. The pressure in the system blowing hoses and heat at highway speed really lead me to think of a partial blockage in the system creating increased pressure. Have you tested the radiator? The loss of coolant could be caused by small leaks caused by excess pressure if the coolant is not flowing.

[pwilliam]

No, car has been taken out regularly-its my daily driver but I purchased it back at the beginning of January. PO said he drove it around town often. I'll try running some water through the heater core as well, this weekend to see if there is blockage there.

[TX82FIAT]

There is a blead bolt for coolant on the block exhaust side as well. You may be able to tell something by comparing flow rate coming out of the bottom of the radiator with the engine block blead closed and then the reverse with the radiator blead closed and letting the coolant flow from the block. Coolant issues can be a PITA. Stick with it. It took me several weeks to find a small leak right at the heater pipe and water pump connection. some folks on the forum suggested the use of a talc powder. That was the only way i could see the very small leak.

[majicwrench]

Didn't you say heater cranks?? If so, no need to flush heater core.
Radiator cap will let off excess pressure, you cannot build any more pressure in system than cap allows. System needs some pressure to work properly. When hot, yes, hoses will be quite firm as they should be.

IF you jumper fan--it runs right?--- will that keep the system in the proper range??
Keith