It's hard to believe that the heater would have that much affect, but I suppose it's possible. Old (well, maybe not so old) trick for an overheating engine up a grade is to run the heater and its fan to help cool the engine. So perhaps if you're getting some natural flow of air across the hear core, it could affect it if the heater valve is open. It doesn't seem to me that a restrictor in the heater line is the answer, but rather the valve itself. Maybe you can simply try a U shaped piece of hose on the water pump in/out like Speartech uses (and just bypass the heater core) and test the result. If you don't want to buy that piece, you could rig up a 5/8 hose and 3/4 hose with a reducer in between just for the test. At least you'd eliminate the heater as part of the problem.

I couldn't find a manually operated heater bypass valve, but I did find one from a '90 Chevy Astro Van that looked like an easy fit for a custom setup. Even if I have to modify it, I think I'll use it on my swap (unless someone knows of a manually operated one).

Andy1

 

Well, Andy1, I think I need dto do the test like you describe. I have the steam vent going now, and still running cool.

It may be that this engine is so efficient cooling that I need to do the 'ole cardboard in front of radiator thing.

Bypassing the heater core will be a little effort. My outlets from the pump are AN, so I can't just hook a hose there.

Sigh...never easy.

I guess too cool of an engine is better than overheating.

 

I have a question about the heater connections on your water pump. I may have read incorrectly, but I thought they were both on the water pump. One on the suck side of the impeller, and one on the blow side. I'm probably wrong, but that seems like it will cause the problem you are having. If your thermostat is closed, because your engine is running cool, wouldn't your pump be circulating the same water over and over again through the heater core? That same water would eventually lose its potential to put out heat. If it flows back to the suck side of the empeller, it would only be picking up the heat from the surrounding metal in the water pump housing until it gets to the blow side of the impeller, and then it would be back to the heater core again. This seems like it would not allow your heater core to put out much heat if your engine is already running cool. I have notice the supply line for the heater core come off the intake manifold on most engines where the water has a much greater potential to pick up heat. So when the thermostat is closed, the water goes through the water pump, part of the intake manifold (or even through the cylinder heads), to the heater core, and then back to the water pump.

Ok, suppose the thermostat opens and hot water is allowed to circulate through the radiator and back to the water pump. Even though the water just came from the radiator, shouldn't it still be hot enough to put out heat if it is now pumped through the heater core? It didn't lose all its heat in the radiator, but it is certainly cool enough to cool the cylinder heads. Also, the thermostat is now open because the water in the engine is hotter.

If you can find out why your engine is running cool, please post it. I have a ford explorer and I have the same problem. I have tried two thermostats. The later thermostat is a ford motorcraft 190 degree that I bought at Orielly's auto parts. You can cool an engine down by running it rich, but I don't know how much, and I am getting 21 miles per gallon on the highway. I don't know of any other way to cool an engine down. Maybe the thermostat is staying open a bit? Hope some of this helps.

 

Well, I follow what you are saying. although I'm not in the know enough on the flow of that engine to comment.

To your question, though, I can tell you that yes, the lines to the heater core are as you describe: one on pressure side, one on suction side right at the water pump. I had earlier commented that it seemed like both being right there would be a problem. But per the reply from Andy, it turns out that the Thermostat has a piece that blocks the path of the water going into the other side.

Your scenario may play into what I am wondering if the problem is, and that is that I do not have a bypass on the two heater lines. The water is essentially forced through the heater core because of no bypass when teh heater core is closed.

Although, again as Andy1 said, it would seem odd to me that just the heater core could cool the engine that much.

And, I can tell you for sure, that my engine runs particulary cool on cool days. The radiator MUST be playing into that. If it's 80 outside, the engine will run at 175. If it is 60 or less outside, adn I'm going 55, it will barely come of of the Cold marker on teh thermostat.

Even though I tested the thermostat on the stove using a temp gun, I'm still tempted to replce the thermostat. Altough I fear I'd just be wasting $15.

I'll definitely post back if/when I figure it out. ONe of these days (it'll be a bit) I may try bypassing the heater core altogehter and see what happens. I don't expect it to change.

By the way it was described to me by Mark at S&P about how the engine itself acts like a radiator, consistently flowing water through the engine, not allowing for hot/cold spots as older style engines do. Can teh engine be that successful at cooling? At this point I don't know. (Oh..Mark wasn't implying that the engine was taht successful at cooling. He was just describing how it worked. His suggestion was that water throught the heater core was the problem, and I should put a restriction in the heater hoses. Not quite sure how to do that yet.)

 

I may have some useful information.

I put a 180 degree thermostat in a pot of water and watched it closely as it heated up on the stove. The thermostat started openning at about 184 degrees and the hotter it got, the more it opened. As it cooled, it did not FULLY close until it was down to 170 degrees.

Also, I took my radiator cap off and watched the coolant in my radiator as the engine warmed up. At first the coolant level rose very slowly. I was told this is the water expanding as it heats up. Then the coolant level dropped about 2-3 inches. I was told it would drop as soon as the thermostat opened and allowed the coolant to flow. The water level drops because, there is now water in the upper radiator hose on its way back to the radiator. The water pump sucks the coolant from the bottom of the radiator.

So I think I realized how the engine temperature is being set by the thermostat. Apparently the thermostat always stays open to some degree. If its a hot day, the engine should run a little hotter, because the hot air does not cool the water in the radiator as efficiently as it would on a cool day. Therefore, a higher flow of water would be needed through the radiator. A higher flow is achieved as the engine heats up and allows the thermostat to open up more. The coolant temp will heat up until a balance is found.

RPM also affects the temperature of the water. If your water pump turns faster, it will force more water through the same size opening in the thermostat. More water through the radiator will cool the engine more. As the engine cools, the thermostat will now start to close until the proper balance is found.

Since I was able to verify that my thermostat is staying open, I may need to use the factory 197 degree thermostat in place of the 190 degree unit I currently have installed. Maybe this will make up the difference. I've really been going by my temperature gauge reading to determine my engine temp. This is true as long as my temp gauge and temp sending unit are accurate, and there is no corrosion in the connection for the temp sending unit. I don't know of any other accurate way to check my coolant temperature.

I was also told to never buy an after market thermostat, even if its the same temperature as the factory one. The quality of the materials are poor enough that it is not worth the lower price. I was also told this by someone who sells aftermarket parts. I am almost convinced that if your engine temp is running too low, the problem lies in the thermostat. Previously, I did not think it was my thermostat either, but now I believe it is. By the way, please do not put a piece of cardboard in front of your radiator. This will increase the engine temp as if it were a very hot day, but your thermostat would be wide open, and your engine would not have any more cooling capacity if it needed it.

 

Interesting information.

The other day when I put my thermostat back in, I started the car and watched the radiator, and the water did start to rise after a bit. So, I capped it so it wouldn't overflow.

I'm not quite sure what to think. It does seem like it would be the thermostat. Your point about it not closing until 170 is intersting. I sort of watched that, but not that close. I had decided it closed at a higher temp, but wasn't as concerned, so didn't note that closely.

But, it seems to me that the engine is runnign quite a bit cooler than that when I am driving in cool weater. (I need to take my temp gun with me and register stop sometime and take a reading of the temp on teh heads then). Not only is the pump moving faster, but cooler air is coming through the radiator. If that is getting through the thermostat, then there we go. But again, if the stat is closing at eve 170, I'd think my heater shoudl put out enough heat.

Regarding the suggestion to not use cardboard, I understand what you are saying. The problem would be if all of a sudden it's a warm day and I need cooling capacity, I'd then have to stop and pull off the cardboard. Of course, I anticipated putting somehing there with some holes for some flow.

This is pretty frustrating. I supposed I should spring for the small number of $ for a new thermostat and see if that helps. I can't imagine that restricting the flow through the heater hose like S&P suggested will help. I am still curious if the bypass on the hoses not being there is part of my problem.

 

Well, I tried a couple of things. I put in a new thermostat. I bypassed the heater core. And I put a restriction in the heater hose.

Nothing helps. It still runs cold.

I may have to give up and presume this engine just runs cold. Sucks when I need a heater.

Oh, and I'm told that if the engine doesn't get to a good warm temperature that the computer runs in closed loop (or is it open loop...I don't remember which), effectively using a 'default' gas mixture, rich, and resulting in poorer gas mileage.

I don'td know what else to do.

 

None of this has been making sense, it seems it MUST be water getting past that tstat somehow.

I found that the new tstat I purchased from GM was not quite fitting right into the S&P swivel housing. It wouldn't quite seal tight and I had a leak, so pulling the housing and tstat, I see that it was just a bit larger than the one that came with the housing. I also found that the one that shipped with teh housing seems to rock just a bit when in the landing for it. So, thinking maybe, just maybe, it was letting a little water get through.

So I called Mark at S&P to ask about the tstat housing. During that discussion, this info came up: 2003 and older tstat would be part of the housing. 2004 and newer the tstat would be a separate tstat.

While I was told this engine was a 2004, the fact is that my tstat that came on this engine is part of the housing. Mark says that it will make a difference and I should have the one he makes that would replace my original, i.e. one that is built into the housing.

So, I have a new swivel tstat housing on the way from S&P. Hopefully by this weekend I'll have a warmer engine.

I'll keep y'all posted.

 

Roger,

Thanks for sharing your findings. Apparently I will need to check my set up a little closer, as I have an LS2 water pump on my LS1 (for the shorter pulley). At first glance, the thermostats and water necks look the same. I'll double check.

On my 2001 LS1, the thermostat can be separated from the housing so I never quite understood what is meant by the thermostat being part of the housing. Yes, I see them listed as sold as one unit in the catalogs.

Andy1

 

Glad to share, Andy1.

Keep in mind that at this point I do not yet know that this is my problem. But if it isn't, I am at a total loss.

I'll post back once I have it in and tested.

 

Well, I am feeling positive. I'll have to post back after some cool weather hits. It's in the mid-80s now.

But, I put in the new Tstat/housing, and the temp runs at around 175-185 consistently. It is not cooling down from that while driving 55, so I'm thinking I'll be OK. I'll post one more time for verification after I hit some cool weather .

 

hook the radiator hoses up backwards? WHAT?!?! No man make sure you have the correct t stat for your water pump. It blocks a passage inside the water pump and there's different configurations. And it's got nothing to do with your steam vents you're wasting your time

 

The poster you are replying to hasn't been here for quite a while. Check post dates....
And don't type in boldface. It's like you're yelling.