LSx running hot only at idle

[streetk14]

I have a small problem, and was hoping someone would have a solution or some suggestions for me.

For those who don't know, I recently did a Magnacharger install on my '67 Camaro. I also did a head, cam and header swap prior to the blower install. I have been driving the car, and getting ready for the dyno.

I have noticed the coolant temp readings on my gauge will creep up when the car is idling. This has nothing to do with road speed or air flow through the radiator. The coolant temp is usually at around 160-170 when cruising around, but will slowly climb to 220 or more if I let it idle for long periods. If I increase the engine rpm to 1500 or so (with the car still stopped), the temp will drop back down rather quickly. Since I have electric fans (which come on at 180 degrees and are running when this happens) the only thing the rpm increase is doing is increasing coolant flow through the system.

This makes me think it is coolant-flow related, but the coolant flow from the upper radiator hose with the engine running seems fine. The cooling system seems to be bled properly, and like I said, this is only at idle speed.

There is only one thing that I can think of that would be causing the problem, and hopefully some of you LSx guys could tell me if that could be the case. I had to change the front coolant bleed pipe (the one that connects the cylinder heads at the front of the motor) when I did the blower install. The new pipe puts the barb (that goes to the radiator on factory cars) in a different location to clear the blower manifold.

On my motor, I run the coolant bleed pipe hose to the top of the water pump (I drilled/tapped a hole and installed a fitting), and have been driving the car this way for a while without issues. When I installed the new bleed pipe from Magnuson, the position of the barb changed and it appears that the hose that goes from the water pump fitting to the bleeder pipe barb is kinked. I am thinking that the kink in the hose could be restricting coolant flow at idle and could be my overheating problem. When I increase the revs, the additional flow/pressure could overcome the restriction in the hose and the problem goes away?

I guess my real question is this: what would happen if the coolant pipe was blocked or restricted on these engines? Could this cause my problem? I've heard it called a steam pipe before, but don't really know what it's purpose is in the cooling system. I'm going to try to re-route the rubber hose so it is kink-free, but wanted to get some opinions.

Sorry for the long post, just wanted to get all the info out there.

Andy

[WS6]

Thorough posts are great with a situation like this. I should hopefully have time to thumb through some of my C5 Service manuals tomorrow to see if the books give any specifics on the steam tubes. I would definitely get the kink out in the mean time if you can.

[WS6]

Andy, all the books said was that they are air bleed pipes. I'm thinking getting that kink out will help.

[streetk14]

Thanks Trey,
I'm going to try to route that hose differently to get the kink to go away. It's tight in that area since my alternator is up high on the passenger side, so I'll probably have to swing it out of the way to access the pipe & hose. The hose that connects the water pump fitting to the steam pipe is only a few inches long right now, so I'll have to figure out a solution to give the hose a smoother radius.

I've been out of town, so I'll mess with it this weekend. I'll also be installing a 2.8" blower pulley to replace the 3.0" that's on there right now. It should pick up a few psi with the pulley swap, which I want to do before it sees the dyno.

Andy

[WS6]

good luck. Let us know if you still have problems with the temps though.

I'm anxious to see the dyno numbers on that beast too.

[streetk14]

good luck. Let us know if you still have problems with the temps though.

I'm anxious to see the dyno numbers on that beast too.

Well, no luck on the coolant hose thing. I cut it a little shorter and it seemed to get rid of the kink, but the problem is still there. What it is doing is very strange to me.

Today, I took it for a little drive to get the engine warmed up (aprox. 160-170 degrees) and then I parked in an empty parking lot and let it idle for a while. After 5-10 minutes, the temp had risen from 160-170 to around 210. I increased the rpm to about 1800 for maybe 15-20 seconds, and the temp dropped back down to 170. Definitely seems to be coolant flow related.

I just remembered that I did have to bend the barb on the steam pipe when I installed it. I don't think anything was kinked when I did this, it just bent a little where the barb is brazed to the rest of the pipe. I suppose there could be a restriction there, but it seems unlikely.

It isn't a huge problem, but is annoying. It's really only an issue when at a dead-stop (like in a drive-through) for long periods. A low speed crawl is fine, since the rpms will be above idle speed.

And just to let you know, I installed that smaller blower pulley this morning. I'm now seeing 9-11 psi on the boost gauge depending on rpm & gear I'm in. I'm anxious to get this thing on the dyno as well. We'll see soon I hope.

Andy

[WS6]

the car was fine temp wise before you did the blower, correct? You only did the blower and now the temp problem? You didn't change to an under drive pulley did you? That would be counter productive to the blower as well. I'm simply thinking out loud. Radiator cap is on fully? T stat wasn't changed with the blower? Fans still sucking air not blowing air?

[4MuscleMachines]

I think it might be the added heat from the exchanger. When you are idling, the heat buildup from both the heat exchanger and radiator is too much for your cooling system to overcome. I live in a hot area and I notice this in my maggied GTO. When I drive or run the rpms up a bit the heat is removed. Also, I don't think that temp is too hot for an LSX engine, they normally run around 210-220.

[streetk14]

the car was fine temp wise before you did the blower, correct? You only did the blower and now the temp problem? You didn't change to an under drive pulley did you? That would be counter productive to the blower as well. I'm simply thinking out loud. Radiator cap is on fully? T stat wasn't changed with the blower? Fans still sucking air not blowing air?

I never noticed this before doing my big parts swap (heads, cam, headers and blower). No, I still have the stock crank pulley, and the radiator cap seems fine. I did not change the t-stat (had a 160 already) and the fans are spinning the right direction. I did get rid of my coolant overflow tank, which shouldn't have any effect on the cooling system operation.

After doing my cam/head swap, I noticed my water pump leaking from the weep hole onto the garage floor. I drove the car for a few hundred miles like this before the blower was installed, and the coolant leak seemed to be minimal. I did not notice the heating-up problem then.

After installing the blower, the coolant leak became very bad and I replaced the water pump. After replacing the water pump was when I first noticed the temp problem. Unfortunately, I did not drive the car very much with the blower before I replaced the water pump (the leak was too bad and I was worried about getting coolant all over the belt and pullies). So, I don't know if the problem is a result of the water pump or something else. After replacing the pump, I let the car idle for a long time which is when I first noticed the problem.

FWIW, the water pump was a Bosch pump I got from Pep Boys. It says "100% new parts" on the box, but was much cheaper than the pump through the Chevy dealer. I think I paid around $130 for it. I wonder if this pump has a different impeller that isn't flowing enough at idle. Just a thought, and I suppose it's possible.

What do you think?

Andy

[streetk14]

I think it might be the added heat from the exchanger. When you are idling, the heat buildup from both the heat exchanger and radiator is too much for your cooling system to overcome. I live in a hot area and I notice this in my maggied GTO. When I drive or run the rpms up a bit the heat is removed. Also, I don't think that temp is too hot for an LSX engine, they normally run around 210-220.

I have a smaller heat exchanger (than the GTO), and it doesn't really block my radiator opening. This problem happens no matter the outside temperature. It happened when I was testing it yesterday afternoon @ 65 degrees outside. I also have a good sized Be Cool radiator.

I agree that 210 isn't too hot for these engines, but the temp will keep rising if I don't raise the rpm to lower it. I've never let it get into the danger zone, but I have a feeling it would cause some serious engine damage if left unattended.

I'm starting to suspect the replacment water pump I installed.....

Andy

[WS6]

You know grabbing a low mileage used one off the net isn't too difficult. Considering how easy it is to replace, I would swap it out and see. If it doesn't help, you can always resale the used one and put the new Bosch one back on.

[streetk14]

You know grabbing a low mileage used one off the net isn't too difficult. Considering how easy it is to replace, I would swap it out and see. If it doesn't help, you can always resale the used one and put the new Bosch one back on.

I suppose that is an option, but most of the ones I've seen on ebay are kind of ugly (rust, chipped paint on pulley, etc.) . Also, my pump is a little harder to replace thanks to my S&P accessory drive. The a/c brackets are a pain to remove, so I'd hate to have to swap pumps a bunch of times.

I might just pick up a new GM water pump and give it a shot. It's a gamble, but it is the best (but most expensive) option I have. If it doesn't fix it I'll be a little pissed, but I can always sell the Bosch pump.

It's funny, after a lot of searching on LS1tech I've found quite a few people with this same problem (one in a '68 Camaro w/ an LS1), but never a solution. It seems that a lot of people ask for help, but don't post the fix when it gets figured out. Either that or the problems never get fixed.....

Andy

[Moose]

have you tried bleeding the coolant system? On my 4th gen to get the air bubbles out I would have to pressurize the coolant system to get the air out. A friend bought a tool from snap on that worked perfectly.

I was thinking a air bubble that gets trapped, and rpms are forcing coolant past it.

[streetk14]

It was that damn Bosch water pump causing the problem as I suspected. I decided to bite the bullet and bought a brand new GM pump from the dealer. At least I get my discount from working at the BMW dealer next door, so the price wasn't that bad.

The new pump was the updated, LS2 style pump and it came with a new thermostat and housing. Since the newer LS2 style pumps have a different thermostat, I was unable to use the 160 t-stat I have been running. I decided to bolt it on as-is with the stock 195 t-stat the pump came with. The motor can now idle and doesn't heat up. It was very consistant tonight, and ran between 185-190 on my temp gauge. I let it idle for almost 20 minutes in the In & Out drive through, and no problems at all. It was probably only 60 degrees out, but the temp would have crept well above 200 with the other water pump, and I would have had to bring the rpms up a little to cool it off.

I am relieved that it's fixed, and I'm going to try to get the car on the dyno this weekend or next weekend.

Andy

[WS6]

Glad to hear it Andy. I am willing to bet that Bosch has a warranty on it and you should be able to return it. I'd definitely try that.

[streetk14]

Glad to hear it Andy. I am willing to bet that Bosch has a warranty on it and you should be able to return it. I'd definitely try that.

It has a lifetime warranty, but the problem is that I drilled & tapped a hole in the top of the pump (on the flat, round pad) for a fitting that connects to my steam pipe hose. Although, I suppose the guy at the Pep Boys parts counter has any clue whether that hole belongs there or not.

I will definitely check out my options. If I could just return it for a refund that would be the best, or maybe for store credit. We'll see, but I am still wondering what caused my problem. Did I get a bad pump, or is the impeller design poor? I guess I'll never know.

Andy