1985 308 Qv, Help!

Dennis, I'm not a mechanic but you ARE! It's just a car, albeit with some peculiarities...Go back to basics:
- fans are doing what they should do, so thermostat is likely OK
- fluid is not contaminated so head gasket is likely OK
- fluid is not overflowing, but maybe you're shutting down quickly enough to avoid this
- you've checked for air blockages
- you've checked for major radiator blockages

What's left?
- Blockage / obstruction further into the radiator
- Blockage /obstruction somewhere in the galleries (possibly from old dodgy coolant or someone using regular water?)
- Blockage in the header tank overflow line?
- Water pump operating, but not at 100%?

Good luck and let us know the outcome.

 

i know of a case where the disk(valve) inside the thermostat separated from the thermostat shaft, blocking water. This gave the exact same result. The guy spent ages to find it. His thermostat looked oke but the disk turned out to be from a previously exchanged thermostat.

 

There are a series of events I would do to diagnose and correct. First I would bleed the radiator. A little air in there and you will see temps rise. Second I would watch radiator temp and verify fans are coming on at temp. I personally I like to run a cooler 185 switch. I would also verify temps at the tstat housing (above and below) looking for a differential.

 

have you confirmed temps with an IR gun or known accurate gauge?

If the coolant system is good then I'd look at a couple other things like,

Whats the AFR reading? is the fuel system and pressures within spec? exhaust flowing freely?

It's hard to say without being in front of the vehicle but temps that hot that fast in cool ambient temps like that, lead me to think that it's lean burning or possibly the timing is out.

Did the engine out service entail anything other then belts and hoses?

 

Change the cooling System thermostatic valve: it's broken and doesn't open completely.

Ciao

 

+1

 

Lets give the OP some apropos as he's a retired mechanic and very well knows his way around an engine, not to mention a cooling system. More then likely he's curious as to if there is a "trait" common to these engines that would result in what he's experiencing.

The next bit is not intended to be a "talking down" to or lecture. The cooling system in every engine is the same, they all operate under the same physics and the same mechanics. The T-stat has a simple job, open at a set temp and close at a set temp. It's a fundemental part of the cooling system that when a T-stat fails to operate as intended it's not that difficult to figure out in which manner it's failed, open or close. How? many ask, easy enough, monitor the thermal cycles. That's a loaded answer full of meaning that is not provided within it.

The mass of the coolant in the engine block is kept more or less separated from the mass of the coolant in the lines and the radiator, both masses are fairly close to each other in volume. The "gate keeper" is the T-stat, when the mass of the coolant in the engine reaches the opening temp of the T-stat it opens and an "exchange" occurs, it's an early analog "smart system", the flow direction is from the engine to the radiator for a very important reason. As the colder coolant mass from the radiator is exchanged with the hot engine coolant a couple things occur,
1. thermal heat is transferred to the coolant
2. thermal heat is transferred to the radiator from the hot engine coolant
3. the colder coolant closes the T-stat
4. the now 'blocked' cold coolant will continue the thermal transfer from the engine
5. the now blocked hot coolant will continue to transfer heat to the radiator
6. repeat

There are a couple things that can go wrong or fail in the above cycle and when they do it affects the cycle in unique ways.

A failed T-stat that doesn't open will simply not exchange the coolant, the engine will be hot but the radiator is still cool or cold.

blocked flow: normally in the radiator, hot and cold spots will be found in the radiator and the the T-stat will be open all the time. Depending on the severity of the blockage will determine how long before the T-stat will no longer cycle.

Here's where I think people get tripped up, the T-stat responds to the environment and also controls it (a regulator). So an improperly operating T-stat vs a problem within the coolant flow can be tricky to sort out. The flow of the coolant is critical for a proper operating environment, too slow and the coolant will have increased in temp to hold the T-stat open. Is the T-stat bad or is the flow bad? or a 3rd option!, is the engine running right? too much combustion heat above the normal operating range makes things to hot even for a properly designed cooling system.

Not seen but does happen, flow that's too fast. Flow that's too fast will also result in hotter then wanted temps but will fluctuate wildly before that. Hot engine coolant and the cold coolant cycle but it's fast, the T-stat will respond however it's operates 'slow' compared to the flow, as the cold coolant is causing the closure if the flow is fast enough the hot coolant will also now be moving back through and causing to the T-stat to pause. or the coolant flow is such that it does close but what happens is the cycles continue to get to shorter until the T-stat holds open.

The mass of the coolant requires a specific amount of time to exchange the heat between the engine and the air, too long and the engine overheats and fluctuates, too short and the engine over heats.

So what's my point with this long diatribe? it's not always the T-stat that is the problem.

To the OP, Ferrari has a published spec on the operating curve of the T-stat, always best to check the T-stat against that insure proper operation of the system. The spec is a scalar function, temp/time/distance.

 

SMG2, one thing is clear: the water flow is not enough. As the fans start turning, means there is not a temperature gauge fail and the problem is real. The water radiator has been redone, so the problem cannot be there. As the water pump was changed, it cannot be that. Unless there is air on the cooling system (I think he already did this check) the problem should be something that reduces the cross section of water pipes. My idea is the water thermostat. Or, if the water thermostat is ok, means the heads are gone and there is a gas leak that goes in the cooling system, causing a water pump cavitation and water flow reduction.

I hope it's the thermostat, or it could be a very expensive problem

 

IIRC, RifleDriver has mentioned in the past that the 84-85 (may have the range wrong) cars had occasional cooling issues the earlier and later cars didn't have or have as frequently. My 81 always ran cool to normal even with glowing headers (another issue being addressed).

I also understand anyone can rebuild a water pump but there is an "art" to it. If it is not done "just so," its efficiency drops way off.

Someone VERY familiar with these cars like him MAY have the answer us mere mortals just may not know.



[No DIS intended Scott]

 

Fans are reactive and only tell you that the coolant has gotten hot enough to activate the switch. Now where in the cycle that happens can be telling. Given that the OP is a retired mechanic and has at this point gone thru the cooling system short of tearing the blot apart, I'd look to see if the gauge is accurate and then if the fuel/ignition system is operating properly. A quick bench test of the T-stat can answer if it's the problem or not. Pot of water, thermal probe and a timer and a scale. Measure the opening points at specific temps and time rates for closure. Something to keep in mind, not all the off-the shelf cross referenced stats operate as the OEM one does. Most are a binary open/close and may have a gap that is too large and allows too much coolant to circulate before it should.

Pump cavitation from low pressure sheer? yeah that can be a problem for flow and also destructive, but I highly doubt he's facing that issue as that's a high RPM one. Now as to the proper pressure of the system? he doesn't say. Back to cavitation at high rpm? yeah that's a problem that can occur due to the blade geometry of the pump and a couple other factors, but would not be responsible for idle temps. I can do an entire post on the stock pump blade geometry itself, but it's not worth my time to educate everyone in the physics of flows, thermodynamics and pump design efficiency. Plenty of searchable info on the web for that.

exhaust gas in the system is easy enough to check and the OP said he did, there is none. Air in the system will reduce pump efficiency but is not called cavitation.

What is cavitation?| Explore | physics.org

It's either a bad T-stat, wrong T-stat or simply a bad sensor or gauge. Failing all that then it's time to look at the combustion temps and ignition timing. A gas analyzer can help speed up checking what's going on with the combustion.

 

None taken

Brian would indeed be the one to know about any specific traits these models have when it comes to a problem like this, if it does indeed fall into that grouping.

Honestly I get frustrated when reading some replies and get why Brian can be blunt with an answer. Most posts are opinions, while they are trying to be helpful it only adds noise. I don't have a magic ball and can not with certainty say what the OP's issue is as I'm simply not in front of the vehicle. All I can offer is diagnostic options based on an in depth knowledge of this particular engine and vehicle systems. This all started as a hobby... maybe I should just go back to full time weapons design again, at least I got to blow things up vs keeping them from doing so

Not to harang on Brian, but I'm honestly surprised he's as composed as he is. I simply stop responding as I do have a penchant for getting vitriolic when frustrated with ignorance. Oh and I'm not picking on anyone specific in this thread, just talking in general.

 

Great contribution by smg2 - good facts and well explained


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Sounds like you ruled out the head gasket.

Did you do the work or someone else for your engine out (which could have been done engine in)?

I would have a laundry list of suspects, but since it has been messed up since the work completed I would go back over all those items you touched. Sounds like you did that with the T stat, the water pump. You rodded the radiator. So its good.

How about a picture of the T stat currently installed? Does it have the block off disc on it? The car is sensitive to the correct T stat. Did you hot pot of water the one you have to confirm the opening temp and correct operation? Are you using higher temp t stats? Does the t stat fit correctly or is there slop in the recess? Did you face the t stat air bleed weep hole at 12 o'clock?

If the car was not over heating on that first drive until you hit the traffic, then that points to fans not up to speed, or hood foam, or the radiator that you have already ruled out. Have the fans been out and miswired on install so that they are pulling rather than blowing? Have the fuse boxes ever been replaced....as I wondering what type of current they are getting when on? Are they both coming on? Is the hood foam there? The piece across the hood that touches the top of the radiator when the hood is closed is fairly critical to force the air through the radiator core.

Of course bleed at radiator and at the T stat housing. I personally do this nose downhill, heaters open, 3/4 fill the expansion, 1st radiator, 2nd the t stat housing.

Speaking of the expansion tank, you mentioned it hasn't boiled over. So how much coolant is in there? My experience is if it was as hot as you mentioned, and the coolant was filled 1/2 way or more on the expansion when cold, there would be coolant on the floor at those temps. So possibly either you don't have enough coolant in there or that temp gauge is wrong. I would check both.

If its staying around the 195 mark going down the road, and then gets hot quick in traffic or at a stop light, that says fans not up to speed with tired motors, or not enough current, or not coming on at the temp when they are supposed, or missing hood foam, or miswired motors.

Now to stretch this into the realm of possible but unlikely.....You mentioned belts. Is the car timed correctly? You mentioned engine out. Did you stuff rags down holes and forget to remove one?

What ever it is, you should be able to get it sorted. I would suggest connecting with a knowledgeable owner in your area and offer up a beer or two for a few hours trouble shooting.

 

Just a thought check the routing of the radiator hoses..... I was working on a pantera that had that problem and drove me crazy until I looked at the radiator hoses and found the thermostat hose was going to the bottom of the radiator. I found out later that the customer had a repair shop had engine out to replace oil pan gasket.

 

has car boiled over
if not I'd ignore the gauge
have you taken the actual temperature of the coolant in the recovery tank
does your thermostat have that little hole and is it in the correct position

 

I noticed no one has mentioned the overflow cap( aka radiator cap) or maybe I missed it. I had the same problem with the exact same car 85QV. Replaced the cap with Stant #10331 and problem solved. Runs 195 degrees in any condition and never overheats.

If you don't have the proper pressure or not enough pressure due to leaky cap, then you will not have proper coolant flow.

Best part is it only costs $7 at your local parts store and even available on Amazon.

 

Yes, I just wrote my opinion. Nobody can solve the problem without seing the car in person and doing some proper checks. If you ask me a question, I will try to answer with what I know and the experience I had. I hope DCB can solve his problem, I don't want to write "I'm the only one here that knows something about phisics and engines", like someone else did: there are many here that know many things about those engines (but a cooling system is always a cooling system, the Ferrari one hasn't much differences from the others) and have a lot of experience. I just say this: I saw many times a problem like that on engines, and the causes were (a list of what happened, not together, of course):
broken water Thermostat, gone head gasket, a very very small pore in the aluminium of the head, weared waterpump impeller, waterpump belt not properly tight, not enough pressure on the cooling system at the suction side of the waterpump (of course this problem appears just when the water temperature goes up, as the cavitation of the waterpump is much easier when the water is close to its boiling temperature, and if you don't have a pressurized system you can have cavitation at the waterpump suction, and that reduces the waterflow so you have higher temperatures. The higher is the pressure at the suction, the less is the probability of cavitation), dirty in the water radiator. I think jlc 308 could be right, as many others: causes could be many. We are not magicians: those are all aspect to check, maybe better starting from the easiest ones.

Good luck, said from one that is not God and is not a magician nor knows everything: maybe I'm wrong, of course but my job is in the HVAC systems projects so, at least, I don't write what I don't know.

I would try to do at first what JLC308 said, that is replace the expansion tank cap, and just then check the thermostate and the other possibilities.


ciao

 

Get another set of good eyes on the car. You are missing something and if you are missing it you cant tell us what it is so our suggestions are useless.

I am very familiar with those litmus fluid tests for combustion gasses in the coolant. In a clean running car there is usually far too little measureable gas to cause a change. They worked great in old dirty motors but I have zero faith in them from direct experience for cars of that age and newer.

 

Has anyone ever considered that the aluminum sleeves are the problem? They are unique to QV's. Started with QV, stopped at 328. Just a thought, as mine had a tenency to run hot. Could be something else though, as I'm disassembling my engine, I'm looking for clues.

 

I believe the aluminum sleeves were specifically to improve cooling.

 

Not sure what you meant by original cap, if it is more than 5 years old I would toss it and get a new Stant 10331 for $7