Bubba91

Hello Everyone,

I just had my engine rebuilt to a 383 stroker. The shop couldn't figure out why it was overheating. Without going into a long discusion on the issues I had with these guys, I will just say, I had my car towed home. I have replaced the radiator, water pump, thermostat, upper surge tank, bypassed the heater core, and it still it overheats.

I have ruled out hydrocarbons in the coolant, with a test kit...Did the refill procedure per FSM...made sure the fans come on when they are suppose to (228 and 236 degrees).

I have already spent over $6,000 and still can't drive my car.
Any suggestions are welcome. Dealing with the machine shop, that built the engine is not an option at this point. I do not trust them to touch my car again, for too many reasons to list here.

Symptoms are as follows:
-boiling over with cap off at aroung 170 degrees and bubbles coming up.
-Upper hose hot...lower hose cool
-with cap on over heats past 240 degrees after about ten minutes.
-I don't think the water is ciculating.

I think that they probably used the wrong gaskets, and if so...How do I find out? Does this sound like an problem occuring inside the engine?

Thanks,

don hall

I concur with your assessment that the water is not circulating, either a gasket blockage, or faulty impeller,
etc.

You might try removing the t-stat, and adding a soluable dye to see if the dye returns to the radiator.

Red 91

Make sure it has the right waterpump, it is a reverse rotation on a 91 l98.

ex-x-fire

Remove the t stat and take a coat hanger to probe the intake, this checks the gaskets to make sure the fronts are the opened ones.

ex-x-fire

I've seen guys put them in backwards, mostly on chevy vans though. The blocked off part is supposed to be at the rear like in the picture.

Bubba91

I will try this

confirmed that it is the right waterpump

thanks for your response, but I'm sure there is no circulation, which would make this test futile. I had the water neck off and no thermostat, with the engine running and the coolant was just sitting still in there.

I may have to pull the intake. I hope it is not the head gaskets

DanielRicany

I had an overheating problem when I installed my AFR aluminum heads. It wouldn't overheat at idle but as soon as you took it out on the road it would get hot. Never actually overheated per say, but got up to 245 ish.

I tried many things to resolve it. I purchased a performance radiator, a high flow water pump, new thermostat, it didn't overheat without a thermostat by the way, but that's not the right way to fix it. I went through numerous cooling system pressure tests. After all this the fix ended up being extensive air bleeding recommended by TPIS. What I did to bleed it, and I seriously recommend trying this, is turn the heat on, jack up the right front of the car, remove the radiator cap, let it warm up till the thermostat opens, hold the RPMs at 3000 RPMs for about 30 seconds to a minute, then increase to 3500 RPMs, fill quickly with water or antifreeze, install the cap, and then let off the gas. You'll need two people for this and it can get pretty messy. Works great for me and the engine has a hard time staying above 190 on an 80* day on the highway with this bleeding method, performance radiator and high flow water pump.

cv67

Sounds lik you got a bum waterpump if theres no water movement with no Tstat in there. Somtimes the impeller can break off and just sit in the housing or you got the wrong one altogether

mtwoolford

The whole idea in cooling an engine is to get ALL of the coolant to circulate into and through the radiator where it can be cooled. Unfortunately, for reasons discussed later, the factory didn't build 'em that way.

Bypassing the heater core only makes a bad situation worse; instead of hot water circulating through the heater core and being cooled somewhat, even with the heater "off" now the hottest water in the engine, directly from underneath the thermostat housing is being fed directly back into the suction side of the water pump where it's sent into the engine. How's that gonna help? short answer, it's not. Best solution? put a small inline valve in the heater hose from the tstat housing to the heater core and leave it closed; at least until winter when you can then open it since you may need the heater / defroster.

You replaced the water pump? aside from making sure the pump is designed for the correct rotation (a serpentine belt rotates the pump opposite from the older v belt, pulley drive), in a situation where cooling has become an issue, bust the bucks and purchase a high quality, high performances water pump, the big difference being that a stock pump uses a stamped tin (okay maybe stainless steel) impeller with flat vanes that is very inefficient compared to a quality pump with a fully machined impeller with curved (not flat "paddle wheel style) vanes.

lastly, don't overlook the oldest racing cooling mod in the history of the small block; when the pump is off, on the driver's side of the engine, there are two mounting holes, and a third hole. BLOCK OFF the third hole, either with a pipe plug in the block, or at least a piece of stainless steel shim material. Why you ask? well because that passage is designed to bypass any cooling by taking hot water from the block and sending it directly into the suction side of the pump, which is great, if you're in Minnesota, trying to warm up the engine on a freezing winter's morn, but pretty useless in your situation. BTW a high performance pump will probably have this passage already blocked in the pump body.

finally, to eliminate any thermostat issues, especially during the initial startup, trouble shooting phase, chuck the thermostat and replace it with a restrictor plate; circle track suppliers sell them with various i.d.'s, but for your purpose, just take an old thermostat, clip out and remove the center "pellet" and install the flat ring by itself, essentially mimicking a thermostat that's one hundred per cent open.

assuming the rest of your cooling system is in good order...and really you've addressed most every other issue, these mods will cool that small block of yours. Good luck.

whalepirot

When my 406 was overheating, I also threw parts at it. The cooling system requires the water to remain the int block long enough to absorb the heat and in the radiator long enough to dissipate it. A high flow water pump can worsen this situation. Flow is properly controlled by the right thermostat, which cycles constantly in its function. My problem was solved by using a Robert Shaw 180 degree versus a Stant; the Shaw allowing more flow (It had flow however).

Gee... a $12 fix was nice!

rithsleeper

I don't think this is your problem but I'll give you a long shot just in case. Check to see if your bottom hose is collapsing under acceleration. It has happened to me once and I was shocked when I revved the engine and saw it happen. Just sandwiched together..... Restricted flow quite a lot. If I were you though, I would pull the intake and unfortunately heads too. Get a performance GM head gasket that has larger openings for flow. It really should only take you 6 hours or so to take it all apart and put it all back. Unfortunately you are talking about $100 in gaskets.....

I know it is frustrating.... I'm there now. Now imagine you fix the problem then blow your engine . Get on my level!

Bubba91

Just letting it idle from a cold start up, the surge tank starts to violently boil over at 170 degrees. It won't even get hot enough to allow the thermostat to open. I think the engine builder screwed up the gaskets. Unfortunately, I think I am going to have to pull the intake, at least, and probably the heads.

rithsleeper

Pressure affects boiling point. I don't know about 170* seems low but a faulty cap that won't keep pressure will cause that also. Mine will usually start pouring out if I leave the cap off when the gauge reads 180. Remember depending on where your sensor is, the temp could vary quite a bit in other areas of the engine. Still agree that it needs to be bled, gaskets are wrong, or you have compression leaking past the head gasket that is leaking air into the system. Which usually causes what you are seeing.

Tom400CFI

That^ is not right. That is old lore. You can't flow coolant "too fast" and cause overheating in modern cooling systems.
I find it odd that you posted that...then went on to say that you installed a t-stat that allows more flow. (?) Shouldn't that have caused it to run hotter, according to the first part of your post?

Good reading: HERE


Check the cap (cheapest/easiest) then you could do a poor man's leak down and see if you get air bubbles in your coolant, OR do a HC test of you coolant.

Bubba91

I put on a new cap, surge tank, radiator, and water pump(confirmed the correct one), all within the last week.
I understand that pressure affects the boiling point, but the thermostat should open and coolant level should drop before it volcanos out of the surge tank.
I also took off the water neck and with the car running, there was no movement of coolant in the manifold, which is why I think it is a problem with the gaskets. It should of poured out of there, right?

Tom400CFI

Copy on the new cap...Are you SURE it's functioning correctly?

You are right; the T-stat should open before it boils over, though water shouldn't drop when the stat opens, if the system is bled properly. SInce you're getting "boiling over" before the stat opens, that is evidence that the system is being pressurized by something else. Cylinder pressure? Or a bad (new) cap? Even though the stat hasn't opened, by 170*F, expansion has occurred and the system is or should be under pressure. If you had a bad (new) cap, it could push coolant out.

You are also right that w/the water neck removed, the pump should be pushing water out the neck flange.

ddahlgren

A very simple test of the head gaskets being wrong is to drain the engine block with the water neck off the water should leave the manifold. Fill from radiator and water should come back. I think that should tell you at least some of the holes where they should be. I drilled 2 1/8 inch hole in my thermostat and have the good fortune of having a Stant pressure tester for caps and cooling systems. I filled through radiator and squeezed lower hose every now and then and water dropped fast kept that up until no more can go in caped it and finished by adding slowly in expansion tank. Put on pressure tester at 10 psi and run a few minutes then add more. Did check my cap as well and as expected it failed so a new one. A 100 percent 1 man job as well. Works fine so far. Do you have the receipt for the head gaskets still or the package they came in? Yes they could have been mis-packaged but a long shot on that one.

desertmike1

Bingo.. Unless you live at 26,000 ft altitude there should be no Boiling activity,, Water Boils at 212°f at sea level, increase the pressure to 15psi and it now Boils at 255°f. What your calling an Boiling Event, in reality could be high pressure escaping past an Head Gasket.. Or the real Temperature is much Higher then 170°f and the instrumentation is in error. I would Verify the Temperature readings before going any Further!

Bubba91

I think it may be helpful if I shot a video of what happens. Everything points to exhaust gas getting into the coolant, via bad headgasket or cracked head, but the block check test kit shows up negative for hydrocarbons. Also, the lack of circulation issue is definitely a weird one. Could be a separate issue or related.
I'm just so bummed that after spending over $6000 I still can't drive it.
I've had this car for 11 years and will keep it forever. If I wasn't so attached to it, I would have gotten something else with that kind of money.

ex-x-fire

Remove the heater hose that comes from the intake, not the one that goes to the water pump, start the engine. Does it pour out like a garden hose?
Air trapped (or created from head gaskets leaking) in a cooling system expands a lot when heated, that's what's causing it to puke. Your gauge might be reading 170 and another part of the block is 260 because there is no flow or a lot of air.