adtbrown

Yep. Simple as that. Digital and analog confirms higher 6th gear temps. It does this regardless of outside air temp or speed. I was hoping the problem would go away with a recently installed high performance / high capacity radiator. Is it running too lean in 6th? Timing advance? Bad knock sensor? When I shift to 5th, temp immediately drops. Thoughts?

adtbrown

BTW, car is completely stock with exception of a pair of flowmasters, and condition exists with or without A/C or heat on.

93 ragtop

I believe the problem is the motor is under a load, "creating heat" and the mechanical water pump is turning too slow to cool. I have heard others say this as well. You could go to an electric pump or better yet, put in a set of 4.10 gears!!!

c4cruiser

I would check for any dirt or debris that may be reducing the amount of airflow through the A/C condenser and radiator. Not enough air and coolant will not cool down quickly.

With the engine under a load like 6th gear, the water pump is not circulating water as fast as it would in a higher RPM range.

desertmike1

Maybe your Tstat isn't opening fully, worn impeller in the water pump, leaking head gaskets will cause this, hose collapsing... there are a many possabilities..

How hot is Hot?

adtbrown

Gets up as high as 205. I thought of air flow, so I installed a new condenser and radiator. It also has a new thermostat and new water pump. It's done the same since I got it 6 years ago. I thought about the RPM issue, but running it at a similar RPM in 5th as it would be in 6th by changing my speed, it stays cool. At 1500 rpm in 5th, no problem. At 1500 rpm in 6th, temp hits 205. Its really a head scratcher... You would think that at a slower speed in 5th it would be warmer due to less air flow. I was hoping it was just an issue with the computer leaning out the engine to save gas. Even so, I'm disappointed that the new radiator isn't able to compensate since it is a higher quality piece than the original I replaced it with.

JackDidley

205* is not overheating. Its normal.

wingnut96lt4

205. tHAT IS NOT ENOUGH FOR THE FAN TO GO ON 265 is very hot that would be overheating What year?? LT 1 LT4 ???? fan comes on at 228 second at 235 I don't think you have a problem. Could be wrong

adtbrown

Yeah, 228 / 235 is out of the question. I know that's a factory setting, but that is way too hot. 205 is just too hot under a load. I just don't understand why it would run @ 195 ALL DAY long in 5th, but goto 6th and it heats up 10 degrees. I've done some checking, at very least, I'm gonna get it chipped and put a 180 stat in it. At this point, that's all I know to do to keep it under 200. Gonna call a few people that do the aftermarket programs on the ECM's and see if there is anything else to it. That's all I know to do at this point. No reason for it to go over 200 with a 195 thermostat. It doesn't do so in any other gear, even when I'm getting on it. I would expect it to warm up a but when it's being driven hard, but that's never been much of an issue. In fact, I've never seen it go over 200 under those conditions. Just really weird that it would hit 205 with the cruise set at 80 mph on a cool day and flat road.

BTW, it's a 93 LT1

Churchkey

If it is running over the thermostat temp now a lower temp stat will not make a difference.

If a Stewart water pump is available for LT motors it will help. A smaller diameter water pump pulley will move more coolant during 6th gear low rpm high load situations.
Also add a good engine oil cooler.

Luck with your project.

93 ragtop

Im sorry, but you got all kinds of stuff wrong here. No LT1-4 came with a 195 t-stat. Due to reverse flow they use a 180 from the factory. As far as I know, the only change that can be made is the 160 aftermarket.
As already stated 205 is not hot at all. IMO going down the highway going over 220 or so it may be starting to have a problem. But you are not overheating until you get to 240.
Once you get to 30mph or so, going faster does not really help with the cooling (air flow) . But going 60mph in 6th gear at 1200 rpms, well the motor is under a load, but the pump is spinning slower so the temps in the motor will go up a little. That is normal.
IMO 160 may be a ideal temp. to start a drag race from, (at least for me it seems best) But you need the oil to get up in temperature to evaporate the moisture etc. out of the oil. For a street car 205 is not bad at all.

93 ragtop

[QUOTE=Churchkey;1583993575]If a Stewart water pump is available for LT motors it will help. A smaller diameter water pump pulley will move more coolant during 6th gear low rpm high load situations.
Also add a good engine oil cooler.

Luck with your project.[/QUOTE]


LT1 waterpumps are not belt driven, they run off of the timing chain. As far as I know, the only aftermarket support is electric water pumps.

theadmiral94

adtbrown,

I sympathize with your plight, and whereas 205 is not overheating, it is puzzling why yours appears to only do this in 6th gear.

My 94 does a similiar thing, except that it seems to heat up a bit (over the typical 194 digital to a similar 205-207) if in 5th or 6th (and really all gears), so I have narrowed it to be whenever the RPM is below 2k and presumed to be that the water pump is not moving the amount of water needed.

My 94 (100k miles) has a new stock (delphi) radiator, with a few years old OEM air dam, but the water pump and hoses appear to be original.

Presume your testing has been on same road, similar ambient outside temperatures, and just a difference in speed, but otherwise RPM is the same.

So truely your only difference is road speed (MPH).

I've not heard or read of anyway the PCM could know what gear the car is in, but it does know the MPH, so your speculation that the PCM is adjusting something is possible, however, rather than chip or reprogramming or other approaches, what about just using a computer capturing program to examine the mixture cells (BLs) while driving via some free programs which only require a cable to be purchased.

However, another more simple thought.

Could it just be an air flow issue where the faster MPH causes air to NOT be directed up into the A/C Condensor and thereby the radiator?

This could occur if the air dam is damaged (even slightly), or deflecting due to air pressure, or the air is slipping under the air dam and backing up in between the engine and the radiator, effectively preventing the air from flowing through the radiator.

Have you replaced the air dam? if not, that might be a simple area to start.

There is a 'big mouth' aftermarket device which is touted as doing a better job of capturing and directing the air to the radiator, perhaps that is something else to check out.

adtbrown

Wow! I never even thought of the air dam! Mine is in good shape, but it's seen a curb or 2. I'll change that next. Another thing I didn't know is that it uses a 180 tstat from the factory. I've changed it twice since I've had the car, and they always list a 195. I'll put a 180 in it and see what that does.

I haven't contacted anyone just yet about getting it chipped. If nothing else, I DO want the fans to kick on sooner. My thought was that although the computer doesn't directl link to the tranny, it could, however detect the road speed and RPM, and go into some kinda EPA friendly lean mode. If so, I would want to do away with it. Good info guys. Thank you. I will be sure and update the results after I make these changes.

BTW, I know most don't seem to think that 205 is hot. No. Maybe not, but the more consistent and cooler the engine temps, the happier the engine is. It's always been my experience with aluminum heads that keeps them cool helps them live long. I've seen many many front wheel drive GM cars get driven without the AC working and with the fans kicking on at 230 or 235, it's not long before they blow a head gasket, or in a few cases, on early 90's Cadillac 4.9 V8, it stripped the threads for the head bolts out of the block.

c4cruiser

The reason that LT1's run at higher temps is for emissions. High temps help to burn off pollutants. GM has used aluminum heads in Corvettes since the middle of 1986 and there isn't really a problem.

If you have to have the car emissions tested, lowering the coolant temps too much may cause the car to fail the test. Later year C4's that are driven in climates found in southern California, Arizona, New Mexico, Texas and other places will see much higher ambient air temps and those people don't seem to have an issue.

GM does extensive testing of Corvettes in Arizona where air temps could be 110 and higher. The C4 was no exception.

adtbrown

Thankfully, I don't have to do any kind of emissions testing. Might as well get it as cool as I reasonably can since it's not an issue. For what I'm doing with it, no need to keep it consistently 160 degrees, but I'd like to see a fairly constant 180. It might run another 100k miles at 205, but no need to do so if I don't have to. No matter how ya cut it, aluminum will last longer, and be more reliable at 180 than it will at 205. Even at that temp, the less it fluctuates, the better.

adtbrown

Here's a dumb question : anyone thing 1:6 rockers arms would hurt or help?

93 ragtop

[QUOTE=adtbrown;1583996284] I've changed it twice since I've had the car, and they always list a 195. QUOTE]




Does the thermostat look like this one?

http://www.ebay.com/itm/Hypertech-1008-Powerstat-160-Degree-Thermostat-GM-LT1-/360652634632?pt=Motors_Car_Truck_Parts_Accessories&hash=item53f8927a08&vxp=mtr
The standard smallblock looks different and is different. It looks like this. http://www.ebay.com/itm/Hi-Flow-Thermostat-160-Sbc-Bbc-HiFlow-160-degree-Fits-Camaro-Chevelle-/140954892578?pt=Motors_Car_Truck_Parts_Accessories&hash=item20d190f922&vxp=mtr
Here is a link to autozone and the standard t-stat for a 93 is this
http://www.autozone.com/autozone/par...834_1632_93207


At any rate, if you are trying to get the car to run cooler, go to the 160. I can tell you that even on cool days mine still runs 178 and up with the 160. Again, its due to the reverse cooling of the LT1.
Do some research on it and you will see that basically the location of the t-stat is different then the SBC Gen 1 motors.
The water goes into the heads first. This helps it to be able to run a higher compression without spark knock by keeping the combustion chamber cooler, then it goes into the block at a higher then the set temperature (180 stock) This is the reason that the block will be just as hot on a LT1 with a 180 as a standard SBC will be with a 195. I may not be wording this well, but again research reverse flow.

93 ragtop

Quote:

Originally Posted by adtbrown

Here's a dumb question : anyone thing 1:6 rockers arms would hurt or help?

No assuming they are roller rockers, the friction is less, so the oil would be cooler if anything.

65GGvert

One problem with trying to fix a problem that doesn't exist is, you don't know when you're done.