I have a bit of a problem
cooling problem

heres the situation, the car seems to get hot, according to the gauge, the sender is mounted in a non stock location. That non stock location is in the passenger rear of the cyl head its usually on the driverside up at the front

its always done this but its getting worse it seems now that the weather is cooler
I had a 160 stat, when i would drive the car, within a few mins the temp gauge would SHOOT up to 300 degrees way off the chart
my cyl head temp gauge which is mounted on a spark plug on the driverside head only reads 200 degrees
the thermostat has yet to open
BUT
if i rev the motor up, the temp drops, but will quickly go back up
the temp will stay WAY up until the thermostat opens. So im inclined to believe the water temp is actually reaching that. I recently switched to a 180 stat, and the temp seems to ALWAYS stay up past 300 degrees unless i disconnect one of my fans so that the radiator can maintain heat above 180 i guess so that the stat will open and then the temp gauge drops and maintains a steady temp under 220

i put a restrictor in the block in the water pump bypass hole and i also drilled the holes in the T stat
made no difference other than making the situation take longerto happen

My theory is that somehow there is no water circulating at the rear of the block especially on the passenger side which is where the bypass hole is, my manifold doesnt have a water crossover at the rear either (only manifold ive seen with one was my stock one) and only water circulatiing from the water pump directly up to the thermostat and through (cool water) thats keeping the stat closed and not permitting a free flow through the block so that the rear is getting real hot but the front isnt
this is not good

thats just my hypothesis.. any ideas? I just installed a dual fan setup, and when both fans are on the problem is WORSE because it seems they keep it cool enough for the stat to stay closed but the rear of the block to get hot
thats just my guess.. all i know is this cant be good for the car

I was thinking about using the port where i currently have the sending unit in the passenger side rear of the head and putting a pipe or hose with like a 90* bend back up and out from there and then another pipe into the manifold in one of the ports im not using next to the thermostat
that way that hot water can move forward.. atleast i hope.. or would it be wiser to bring it back to the radiator but with a restrictor or something? any ideas?

Im running out of options here and this cant be good for performance and i really get scared im gonna blow a head gasket or something (its been doing it for awhile but before i had a single fan and a 160 stat so the stat would open and would stay open cause the fan wasnt good enough to get it under 160, so it would only do it (go sky high near 260 degrees) for a couple seconds initially and i would dismiss it.the current setup is WAY good to get it under 180, regardless it shouldnt be doing this either way i dont think)

any thoughts would be appreciated

 

Flush the cooling system

Something is restricting flow on the right bank it sounds like.

 

Have you been able to confirm the actual temperature of the CTS with a scan tool? I would be interested what the CTS is saying.

Also, have you tried testing the sender and the circuit? It may be a bad sender or shorting somewhere.

Other than that, I would have to agree madmax that there is some restriction in the part of the block near where the sending unit cutting off water flow. Since you live in Florida and not concerned about freezing, it is possible that previous owners' used straight water instead of a glycol/water mixture and your system hasn't been flushed on a regular basis. This would cause scaling which reduced your water flow.

This is why I always replace my antifreeze and flush it every 2 years. If your engine has had a power flush in the past, you should have fitting installed somewhere in the coolant line leading to the heater core. That is generally where they put it when you have your system power flushed and don't already have one installed.

 

the cts will read cooler, since its next to the T stat, the thermostat doesnt open (two different thermostats)

I have a hard time believing there is something blocking flow to that side because the car runs cool once the thermostat opens. If the thermostat is closed my temp gauge goes up.. Id think regardless of the T stat being open or closed it would run hot if there was a restriction. Also, i have no indication of the driverside of the block other than my CHT gauge which only reads the temp of the spark plug base. I dont know how much coolant temp next to that has an effect on it.. it might infact be going up as high as the other side. How can a flush knock loose something blocking a coolant passage that just regular coolant circulation cant? I can understand things that are allready loose floating around in the system but it would seem this is lodged in a passage or something

ill flush it but i dont think it will change anything, in which case the next question is if there is anything else i can do, like running a tube from that port in the head somewhere else (i was thinking getting one of those water necks with ports on it and plumbing it there right on top of the t stat)

but is there anything else possible? When i did the water pump i changed the fluid but didnt flush btw (was doing it in my garage)

 

When does it do it?

 

whenever the thermostat is closed it seems

within a few minutes of driving the temp will rise to crazy levels

ill get out, and with the car runnign feel the top radiator hose and can tell the thermostat is closed

ive let the car sit there with the temp needle pegged and after a minute or two, the temp will drop like a rock provided the radiator isnt too cold (only one rad. fan on) and the thermostat has opened

if both are on, it will just stay way up there

it seems to me like the water isnt circulating to the rear of the block like its going from the waterpump straight to the thermostat or out ofthe bypass hole rather than cross circulating through the engine

and somehow when the T stat opens there is much less a restriction and water flows all the way to the rear of the motor

If i just let the car idle with the fans off and feel the top hose, it will take awhile but the temp will go up to around 220 or a little more before the thermostat opens.. and that is just at idle, obviously heat will build up much more quickly under load

if the fans are connected the thermostat wont open but the temp will continue to rise off the chart


im starting to think maybe i should plug the bypass hole completely rather than just have a restrictor there since there is no problem as long as there is flow from the pump through the thermostat


it just seems to me that the block is reaching x amount of pressure and just forcing any new water added back out of the bypass hole which seems to be just recirculating cooler water at the front of the motor (cool water getting pumped in and just cooling things locally as its forced back out)
Does this make any sense? thats the only thing that i can figure just judging from the observed activity of it, and the fact that its happening on the same side as the bypass hole inthe block is also curious. I cannot say for sure that its not happening on the driverside but i would asssume its not just judging by the relatively cool cylinder head temps

When i put the restrictor in the block and drilled some holes in the T stat it now takes alot longer to happen.. before it would happen pretty much within minutes, then drop back down just as quick (under 220, nowhere near 160 which was what my thermostat was rated at) and now its slower and i can see the process on the way to school which is actually worse because now it seems like the t stat never opens. I think this is due to both fans working though which is easily capable of keeping the water temp in the radiator under 180.. and since this cooler water is just circulating at the front of the block its still keeping the stat closed even though the restrictor and holes in the t stat have reduced the water recirculation)

the more i think about it the more i think i might just plug the bypass hole completely but i dont know if my guess is even right




[This message has been edited by Pablo (edited December 01, 2000).]

 

Another thought, have you checked the guage itself? I find that whenever there is a problem with the display unit, to check the sensors, wiring and guage first before I begin anything radical.

Look for a second guage (preferrably) aftermarket from a wrecking yard and test it on the sensor. A high reading may still indicate a sensor problem, which tends to be the problem more often than not.

 

On the restriction issue, if the restriction was small enough to just allow gas to pass through, it would only allow steam to hit sensor, which would account for the high reading, but the low temperture at the T-stat.

 

ooh and to add to that

the driverside bank of cyls has no bypass so no matter what its forcing water to go through the block

essentially the thermostat is seeing the load of just the driverside bank of cylinders since alot of the passengerside is just coming back out

thats a theory
but what keeps coolant circulating to the rear of the block anyways? it would seem to me that enough pressure would build up in the back of the block and the water would just circulate from the pump straight up through the first coolant holes around the 1 and 2 cyl and then straight up and through the thermostat

course if that were happening it would have the rear cyls running hotter all the time and not just when the T stat is closed

i understand the head gasket is primarily responsible for the coolant hole restrictions but if infact there were bigger restrictions to the front of the block then the gaskets would have to be right and left specific since both of my gaskets were mounted with the same side up and they werent left and right specific if the holes were drilled for that purpose then one side would have greater restrictions at the front of the block and the otherside would have greater restrictions at the rear


i dunno im just confused now

 

im pretty sure the gauge is right glenn because it will read just fine when the thermostat is open, and will also drop in temp if i rev up the motor (like when the needle is pegged) if i rev it to like 4000 i can see the needle quickly drop but once i stop revving the needle climbs up again

if i disconnect the fans to where the radiator will reach a higher temperature than the thermostat and the Tstat stays open then the gauge will read whatever temp the system is which would be hotter than the T stat

if it was a gauge problem it would be the most F'ed up possessed gauge in the world being that it would be acting incorrectly in conjunction with all these other cooling system activities

 

I also wonder if this isnt normal at all

perhaps it could be perfectly normal... consider that gm put the temp gauge sender at the front of the head on the drivers side not on the rear of the passenger side
I wonder if i got another stock TPI car (since they dont have a water crossover at the rear) and put a temp sender in that part of the head if i would show the same activity.

Dont the early tpi cars have the fan switch in that port? I guess it would be easy to tell if it was occurring if within a few mins of driving the fan came on despite the gauge still reading under what the fan turnon temp would be

 

If the temperature drops when you rev up the engine (and when the T-stat opens), this indicates poor flow and possibly a hot spot there.

I know GM water pumps are notorious for not producing equal flow in the block. I read an article many moons about this problem and generally the fix was a bypass along with a better pump that had better flow. Damn I wish I had my magazines out of storage. I could look up the article and tell you what they did to overcome this problem.

But you may be right as to WHY GM puts the coolant temperature sensor where it does. I could be that if they placed it in the passenger rear side, they would get too many complaints about this.

 

According to Stewart Components:
"A common misconception is that if coolant flows too quickly through the system, that it will not have time to cool properly. However the cooling system is a closed loop, so if you are keeping the coolant in the radiator longer to allow it to cool, you are also allowing it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the cooling system at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures.

"Years ago, cars used low pressure radiator caps with upright-style radiators. At high RPM, the water pump pressure would overcome the radiator cap's rating and force coolant out, resulting in an overheated engine. Many enthusiasts mistakenly believed that these situations were caused because the coolant was flowing through the radiator so quickly, that it did not have time to cool. Using restrictors or slowing water pump speed prevented the coolant from being forced out, and allowed the engine to run cooler. However, cars built in the past thirty years have used cross flow radiators that position the radiator cap on the low pressure (suction) side of the system. This type of system does not subject the radiator cap to pressure from the water pump, so it benefits from maximizing coolant flow, not restricting it."

That said, I have a Stewart Stage 1 pump ($80) which I am VERY impressed with. My car used to run 240 with the fan on (180 stat). Now it stays at 180 on all except the HOTTEST days, when (in traffic) it gets to nearly... 190!

So, this is a consideration for much-improved cooling. The other thing I would consider is a new thermostat since you seem to be having problems with your current one not opening when it should (maybe?). A new one is only a couple bucks.

But I think you may be right, this may be normal. The sender is usually in a very different location and it may be that what you are seeing is normal for that location in the block.

 

Pablo, you know a TSU is way cheap, get another and put it in the right spot and see what happens...

 

Wait, maybe it has the wrong water pump?

I know the pump on the 79 spins reverse of the RS...

 

I agree with Macgyver, its worth looking into, maybe someone at the store gave you the wrong pump. Check the impeller angle. This is a long shot, but like I said it definitely work checking out.

 

I have replaced the gauge sensor in my car as well and it wasn't like what was in mine originally,,, but no matter where I went, even the dealership, it was the same different design (a spade plug temrminal instead of a round slip-over nub). It gives a wrong reading. I have a 180 thermo in my car and the hose is still cool when the gauge is almost at 220 and keeps climbing after the thermo opens. I know it is wrong because I left the cap off the radiator and let the car warm until the thermo opens, with a meat thermometer (real techy,, I know )in the coolant, the water is 190 while the gauge is creeping close to the red zone (260 I think). Driving around with the fan running and it being 30 out, it holds right at 220 on the gauge when i know it's around 180. I know the pump is good and everything else because it is all new.

------------------
Da Boid

- 4 out of 5 people think the 5th is an idiot

 

im 99.999% certain its not the sending unit
why would it read around 200 or so once the thermostat opens (will only open if the radiator fans are off or if im driving real hard)

it just doesnt seem to me that the sending unit would be bad yet act in unison with 10000 other things like how hot the radiator is, or whether the thermostat is open or not etc. It would have to be one hell of a possessed switch

that 200 is after dropping down from like 260+

the thermostat is brand new

the 160 i had in there before functioned as it should aswell (it opened sooner so the car actually only ran in the red or just a bit high before the red for only a few seconds and then would drop as soon as the T stat opened.. i initially dismissed it as some electrical quirk since it happened so fast but now i notice it will change if i rev the motor etc i dont think its electrical)

the pump is the same pump ive always had and i had it on the stock motor
the car is not overheating in the general sense, only one part of the motor is, if the thermostat is open the car will hold whatever temperature the radiator is at

and currently my fan setup is MORE than enough to get that temperature under the thermostat open temp

ive tested this, to where ive disconnected the fans
let the car get hot enough to where the thermostat opened which the gauge showed the rear of the block to be at 220 when this happened, and then the temp fell some but since the radiator had no flow (at idle) it didnt fall much

i reconnected fans and the temp dropped REAL fast

as soon as it got to around 180 on the gauge i felt the hose and the thermostat closed

at the same time, the gauge started climbing back up after it was cool for a few seconds like as if the flow had stopped and the water just began to boil, the temp slowly but surely (at idle) went up to the stratosphere until i disconnected the fans and let the radiator get real hot (beyond 180) and then the stat opened again and then the temp dropped

i really think that this might be normal temp activity or atleast similar to activity one might observe had someone put a temp sensor in that part of the motor on a stock application but i dont know for sure. What im talking about is localized overheating, thereis no boil over no steam
the car does not do a general overheat at all, if it ever gets hot enough the thermostat simply opens and the car maintains a low consistent temp under 220 as dictated by the temperature of the radiator (if it gets cooler than 180 I surmize the local temp at the front of the block or what is circulating through only those parts that have no bypass holes gets to the temp of the radiator while the other parts are reaching the stratosphere since enough pressure has built up from the heat to effectively push the coolant back out because the thermostat is closed)

the car didnt just start doing this its been doing this since day one if i recall but now that i have a cooling setup that is actually quite effective and enough to get the new coolant (from the radiator) under the rated temperature of the thermostat and hold it there such that the thermostat never opens the hot spot around the sender gets hot and stays hot, real hot
Since i put the restrictor in the bypass hole and drilled the 'stat with three 1/8 holes the situation is delayed greatly (now instead of happening when i pull out of my neighborhood it will happen when im almost to my destination) but it still happens and it seems no less intense

what im dealing with is an issue of flow i think. Im gonna try completely plugging the bypass hole on the block and seeing what happens then, if that doesnt do it im going to plumb a line out of the hole where the temp sensor is back up to one of those thermostat housings with screw in ports and mount my temp sensor in the same spot on the second screw in port

only thing i dont like is that the ports face directly back at the thermostat which is kind of counter flow but im not sure it will make such a difference unless i get any better ideas

[This message has been edited by Pablo (edited December 01, 2000).]

 

I don't know what type of intake manifold you're running but chances are you'd have enough room to make your own rear crossover. It's a bit of a hackjob but it could be done to look really custom.

If you drilled and tapped holes through the top of the manifold about 1/2" or into where the rear waterjacket lines up then ran stainless steel line or heater hose fittings to connect the two it wouldn't look too bad and would function aslong as you had a way around the distrib.

Just a suggestion....

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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration

 

Pablo,

Are you getting flow throught the scavenge hose attached to the rear of the right head? (Where the heater hose is supposed to mount.)

Is the heater core/control valve allowing coolant flow?

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

i dont have a heater anymore vader

and when i did, there was no hose coming out of the cyl head it came off the rear of the manifold where the water crossover was

i tried plugging the bypass hole completely and drilled a couple more holes in the t stat and it didnt fix the problem


so i got a new water neck with two ports one of which im using for the temp sender the other for a compression 90* fitting that is going to a copper pipe under the header and to another 90* compression fitting at the sensor port on the head, i figure they hold 30 something psi of water pressure in a house plumbing sys. it should be adequate for my car i just have no idea how im gonna screw it in though theres not alot of space


as for the manifold crossover, i thought of that but it would take alot of machining, the rear of the manifold has these support risers right over the water ports that id have to machine off