Sable 99 Overheating

[yQuartz]

Stumped
my Sable 99 ohv is overheating, bought used with 83k, previous owner changed fluid once, just before I purchased it. Rust in fluids when I first started to work on it. Overheats at high speeds (70-75 mph) not at low speeds. Overheating is not consistant, I can make same trip several times one time it overheats others not. Once overheating starts I can pull off interstate and temp will drop back down to normal.
What I have done so far
1 replace thermostat, twice. appears to be working fine
2 replace water pump, I thought that was it, all the blades were gone, corroded off. Still overheated
3 replaced the radiator cap, still overheated
4 replaced lower hose, still overheated
5 flushed system 4 times once with chemical flush, still over heated
6 replaced radiator thinking clogged with rust. still overheated.

Other problems; heater not working, likely clogged heating coil, tried flushing forwards and backwards, no luck.
Brought it to a mechanic they gave no suggestions except for what I have already done.
Thought it was a possible leaking head gasket, however no white smoke from exhast, engine runs smooth. Not losing fluids except when it overheats through radiator cap. No bubbles seen in radiator fluids.

Help I am stumped
Randy

[yQuartz]

New info on my 99 Sable over heating. I rev the engine to 3K rpms, fluid level in over flow tank is steady it stays between low and high marks. Let off gas back to idle and the overflow tank fills up and coolent starts coming out of the cap. I repeat, each time coolent is discharged from the cap. (cap is on tight) Temp gauge shows normal operating temp. Eventually I lose enough coolent for temperature gauge to read hot and vapor/steam starts coming out of the overflow tank. Any one have any thoughts on the possible problem?

[rogerlh]

Couple of thoughts.
Is the overflow tank cap maintaining 16psi in the coolant system? I think that is what my 98 Sable does. (I just replaced the tank and cap - old tank was cracked)
I seem to recall that backing off from high revs always caused a "surge" overflow (on some of my previous cars) when running with the rad cap off. Sounds somewhat similar but your "surge" prob seems more extreme I don't think you should lose coolant from the tank cap tho.

Is the cooling fan working?

[tulipsgirl]

Where is the thermostat located on a 1995 Ford/Mercury Sable. Duratec 24-valve v-6 engine?

[yQuartz]

The cap is 16psi and the fans are both working
I can drive in town (stop and go traffic) and never overheat or lose coolent.
Engine runs smooth. I do not think it is a head gasket leak, but it is possible.

I am thinking it is a hot spot within the engine that can be kept cool while engine is at high rpms (pump is circulating fluid faster) and when it slows the water near this hot spot boils and vapor expansion pushs the coolent out the cap. Temp gadge shows normal operation temp when this happens. Only after enough water is lost does it register high temp and overheats.

Reason for a hot spot in the engine? I do not know, may be due to rust deposits that partially block coolent flow? Could a leaking exhaust pipe or exhaust manifold in the engine compartment that blows on the engine cause enough heat buildup? I know car exhaust can be like a blow torch.

[rogerlh]

Driving OK in stop and go = low rpm which is not consistent with your "hot spot" theory.
You might want to check coolant pressure at high revs in case there is some head gasket issue at higher temp/revs that are not apparent at low revs. If you run from cold with rad cap off do you see thermostat open (increase in turbulence) water pump circulates coolant at higher revs. Very evident if you "blip" the engine speed. I think if you have good circulation then suspects could be poor air circulation (blower fans or faulty thermostat kick in for blower fans ), bad coolant thermostat (opening at right temp??). Head gasket leak (exhaust channel leak would blow bubbles and increase pressure in system and blow would also make coolant dirty from oily carbon) oil channel leak would suck coolant into sump when cooling-= water / oil on dipstick) Is cylindar compression normal ? If very high the increased compression might cause a rise in temp at high speed. (?carbon buildup or head skimmed too much??)
My best guesses. I don't buy the "rusty hot spot" but I am not an expert anything.

[Rockaddict]

Does the fan work?

I have a similar problem,, My head gasket had to be changed, still overheating, changed the rad, then all of a sudden my fan stops working, the electronic module was replaced. Worked o.k. for a day or two, now the fan doesn't work, I'm told it could be the sensor or relay fuse.
This is on a 92 merc. sable

[marketwatcher]

WOW, In-Laws have gone through the same stuff!!!!!!!!! He was going to scrap a 1999 sable with only 73000 miles for $70.00 because the dealer told him it would be $3000 to fix. They told him coolant in oil. He could not even donate it because it did not run right. I told him I would take it because I hate to see a good car go to waste. They have in the last 6 months replaced heater core ,all heater hoses,thermostat twice, water pump and various other parts, cv ,new tires ,suspension .All at a dealer! So I guess I will be pulling the engine and going through the entire enginge and cooling system with a fine tooth comb. If anyone has any suggestions or answers speak up please or e-mail me : marketwatcher@bellsouth.com please help! the Car has a lot of life left .(hopefully)

[Yardpilot]

My 1987 Sable (160,000 mi.) was overheating like that. I changed the water pump and it fixed the problem. Sort of. A heater hose blew. Then the top radiator hose blew. Then the bottom one. I suppose I should have just changed all the hoses from the git go. It overheats slower now. I'm wondering if the heater core might be partially plugged. Maybe it gets enough circulation at low speed but not when it's running faster. This car seldom sees pavement. I cured a high idle problem by changing all those crumbling vaccuum hoses. It's a great car for ridge running on gravel and dirt roads. It handles deep snow with the big boys, too. I'm impressed.

Next I need to do halfshafts. The book calls for a special tool to punch out one side. Is that really impoertant?

Yardpilot

[diofan]

Could be one of three things (Or a combination of them)

The coolant Expansion tank has a leak (Fairly common in Sables and Taurus), The thermostat is stuck closed, or the Water Pump impeller has corroded away so bad it needs replaced.

Check for coolant near the water pump. there is a small weep hole there where coolant would leak out if the pump is bad. no leak, pump is good

Check for leaks around your expansion tank. This would indicate a leaking tank.

Take the thermostat out, and put it in a pot of boiling water. If it's good, it'll open up.

[Bbodine64]

I have seen quiet a few sable / tarus heater cores plugged. A regualr coolant flush doesnt do the trick. You have to pull the heatercore hoses off and flush them out. The theroy goes as follows:

You have two passages for your coolant to go. One way for flow is through your heater core, the other is through the block. Not sure of the ratio (lets just say it 40% HC and 60% block). With the HC blocked up you loose 40% of your flow. A regular coolant flush does not fix the problem because its already block, (no brainer) which means any additive you put in won't even reach it to help break down the blockage. This also makes sense of why you dont have heat, no flow through the HC.

So I would suggest once again, take the hoses off and flush the HC. Make sure you take off the inlet and outlet and watch for any debris (most of the time it's obvious if it was blocked) and just flush it till clean water comes out.

If that doesn't work than you have me stumped, because it sounds like you have done everything else.

[Yardpilot]

Blew the HC out, changed the thermostat three times, ran about a Peterbilt's worth of icky caustic crap through it, and it seems to be running fine. If anything, it tends to run on the cool side now. Still trying to find out about changing the half-shafts.

Regards,

Yardpilot

[Old Man Chuckles]

Takes a long time for heater to work. On third dorman overflow resevoir, first 2 leaked. Now test thermostat - not working - test new one and replaced thermostat, 195 degree for 99 Sable. Now resevoir cap blows off. I believe it blew off before also. Takes a long time for heater to work still.

Chuckles

[jd-autotech]

there is a idler pullie under the hood that is famous for going bad. it maybe letting tentioon off the belt and wahla u over heat, i beleive its the highest pullie ur belt rides on,hope that helps

[Old Man Chuckles]

Thank you very much, but I have replaced that particular part already. I believe it was the serpentine belt idler.