Just breaking in the new motor (see sig) and I am plagued with overheating problems after 15-20 minutes of driving.

1) Can the stock radiator from an 88 Vette be pressure flushed, or will this damage the radiator?

2) Could the stock radiator not be up to the task? (although, I don't think this is the case, because the motor won't cool down even cruising downhill in neutral at 60mph

3) I don't have the engine build sheet, my mechanic does, so I don't know what type of water pump is on the motor (other than it's shiny). Should it be the standard or reverse type?

From a cold start, it might run for 10 minutes normally, and then it starts to heat up pretty quickly, almost like the thermostat is staying shut (but I checked it, and it opens at 180)

Thanks in advance!

 

So many things could be at play here, let me try a few:
1) Check with a radiator shop as its kinda their business to know such things, but I think you will be o.k.
2) Always a possibility that radiator is too small.
3) It would be good to check and see that the water pump is proper rotation for your engine - parts mistakes can happen.
4) Are you sure that the cooling system hasd been properly burped to purge trapped air pockets?
5) Your indisclosed displacement wouldn't happen to be based on a 406 type engine would it?
6) If yes on #5, then do you have the proper steam holes placed in the heads - do all the steam holes line up block/gasket/heads?
7) On my 406 I run extra cooling lines from near the water outlet to the back of the cylinder heads for more even distribution of coolant.
8) How thin are the cylinder bores? One of the reasons why larger overbores are a dragstrip only item is because thin cylinder walls will then overheat in ordinary driving.

This should get you started, let me know if you need more.

Thomas

 

Quote from Green Rocket :
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8) How thin are the cylinder bores? One of the reasons why larger overbores are a dragstrip only item is because thin cylinder walls will then overheat in ordinary driving.
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:yesnod: :yesnod: :yesnod: :yesnod: :yesnod: :yesnod:
Yes , I learned that one the HARDWAY

 

The motor isn't really that big displacement-wise, it's a destroked block with an .010 bore-out. Kinda silly all these secrets, but a guy has to have something up his sleeve :D

I did burp it for a while, it seemed to be free of bubbles and whatnot.

If the radiator was too small, wouldn't it at least cool down when cruising downhill in neutral? It won't even do that.

I guess the water pump is the next suspect. Flowing coolant the wrong way can't really hurt anything by itself, can it? (Besides the obvious problems that would occur if the engine overheated.)

Also, what was involved in running extra cooling lines? Tapping the block in the rear? (Wait, that sounds strange :lol: )

Thanks very much for the help, the motor is great fun to drive, if only for 10 minutes at a time!

 

Make sure both your fans are working. Have you converted the senors to 180's?

Are you using a stock chip? My 406 cooled just fine with the stock radiator and pump! However, my chip was not stock and my fans came on at 180 and stayed on.

KM

 

My 88 came with one big fan originally, not the two smaller ones, so I have that, and I have had it jumpered to be on all the time since the motor is being broken in and having these problems...

It's no longer fuel injected, rather carbed, the only thing the ECM is used for is the speeo I think.

 

OIC!

You might try and add a few extra holes in your thermostat. Also make sure your center spoiler is installed. Because our cars are bottom feeders that spoiler becomes really important.

Your underdrive Pulley isn't helping I bet! Is your pump stock or a HIGH FLOW unit?

KM

 

I installed a high flow pump and also plugged the bypass in the block (did the shop do that also?)- then drilled several holes around a standard 160 thermostat-and it heated up the same way you're describing.
I discovered that with all that flow/press. it was trying to push closed the thermostat; so I installed a high flow "balanced" thermostat to solve the problem.
Don't know if this is the problem....just another 2 cents.....

 

88-406 - You're right, the underdrive pulley is probably gonna be switched with the stock one the next time I get her up on a lift.

I flushed the coolant twice and warmed it up. Same problem. It went for 10 minutes or so on the road and then went above 230 (Time to shut down as far as I'm concerned). Made it home and then decided to check the auxilliary fan, figuring that that's the last thing before a new water pump or radiator.

Moral of the story: It's hard for a radiator to work efficiently when there's a main fan moving air towards the engine and an auxilliary fan moving air towards the nose of the car. The Goshdurned polarity was reversed b/c the wiring harness was backwards.

Drive It- What's involved in plugging the block? If it's something that can be done with the car on the ground, I'll try it, but if it needs to be lifted I'll have to wait (My friend with the shop is away for the weekend).

Thanks to all who lent their help, funny how lots of times it's the simplest things. If I had a chunk of time to deal with the car I might have better success ironing these problems out. But I only get to put in an hour here and an hour there.

:cheers: :chevy


[Modified by TrueBlue ChevyDude, 5:13 PM 5/31/2002]

 

Moral of the story: It's hard for a radiator to work efficiently when there's a main fan moving air towards the engine and an auxilliary fan moving air towards the nose of the car. The Goshdurned polarity was reversed b/c the wiring harness was backwards.

Drive It- What's involved in plugging the block? If it's something that can be done with the car on the ground, I'll try it, but if it needs to be lifted I'll have to wait (My friend with the shop is away for the weekend).


[QUOTE]
:lol: Oh yea! check the basics first! Just reminds me of a few things I've done!
You have to pull off the water pump; then tap threads in the bypass hole and thread in a plug. It's the hole below the main passage on the passenger side under the water pump.

 

Might want to try to install a pusher fan in front of the radiator, to work in unison with the puller stock fan.
Also, I put an oil cooler on mine, and it helped keep the engine cooler as a whole as well.
Good luck.

 

Yep, the main fan was pulling air towards the engine, but the aux. fan in front was blowing air towards the nose... arrrrghhhh.... :cuss

The oil cooloer is a good idea, I'll go with one eventually. I'd hate to pay the $400+ I've seen for the Earl's kit with AN fittings... What oil cooler are you running?

 

JFYI

I bought the $130 kit from B&M and will ad the AN fittings myself. I dont kow what the fittings/hose will cost, but I'd bet I'll still end up way under $400.

KM