I have '69 400.

I have replaced the water pump and plate already.

I have a 7 blade fan with no clutch, and a good shroud, around a 3 row radiator.

Around town it runs 200-220 or so.

Take it on the freeway, and it gets up to 230 or more, and when you come off the freeway and let it idle it heats up even more.

The center of the intake manifold on both sides get real hot, even to the point of burning the paint.

Could there be coolant blockage in the intake manifold?

Should I recore the radiator with a 4 row?

Not sure what the next step should be.

Anyone had this hot intake manifold issue?

Any advice appreciated.

Thanks!

A three row radiator is not ideal for a 400, especially if it's an automatic or if the radiator has not been tested and/or recored recently.

Discoloration and blistering of paint on the center runners of the intake is normal. There are heat crossover passages between the heads (adjacent to exhaust runners) and the intake to aid quick choke opening. These can be blocked off with stainless shims or block plates.

Have you verified your temperatures with another calibrated thermometer? Remove the radiator cap while the engine is cool, place a thermometer in the radiator, heat the engine to operating temperature and compare to the gauge.

Does your engine show any signs of overheating such as pinging, gushing coolant, steam or other external symptoms?

Have you examined and tested your thermostat recently?

We verified the gauge with an external digital pyrometer.

At the sending unit the temps matched.

At the "hot spot" in the center orf the manifold, the temps were around to 375 degrees.

The car is getting hot, it will blow the hose completely off the thermostat housing after a freeway run and then parked in about 3 minutes.


This is after 2 clamps were installed.

The car does not ping, or boil over, just blows the hose off

The thermostat is new, installed with the new waterpump a month ago, a 160 failsafe.

I think it is going to be removed next.

The car has an automatic 400 tranny, but it has been bypassed with a tranny cooler.

Do you think the 4 row recore will be much of an improvement?

Thanks again for your response.

do you ghave the X fillers, the masticaed fillers and the lower baffle?
always my first question on overheating...

was it originally a 400? or modified from a 350?

Well, since it sounds like you are speaking greek to me,I have to say I have no idea.

The only thing I know is that the engine has a tag on it stating it is rebuilt by "Power Pak" and that it is a 400.

I have never had the engine apart other than the water pump, in the 24 years I have owned it.

Maybe you could explain where these parts are, and perhaps what their function is?

Thanks for the help,and sorry for my lack of technical part knowledge.

might want to try the simple first. with the engine cool have the radiator cap off . start the engine , let it run till warmed up . check for fluid flow movement circulating in the radiator, to make sure water pump is working proper. may want to replace thermostat next. that would be cheap starting points to look at.

New water pump, water pump plate, thermostat.
The new plate helped a little as the old one was corroded around the holes and some flow loss was certainly happening but that was not the complete problem obviously.

Plenty of flow through the radiator, just maybe not enough rows?

How many rows is a stock radiator for that engine?

In 24 years, has it run hot before? If not, what is different now?

The mastcated fillers are rubbber type peices that seal the spaces on each side of the radiator. The x-fillers seal the spaces at the top of the radiator, between the bumper supprt and the radiator support. These help channel the air through the radiator, and have been found to make a significant difference.

Switching to a 4 core from a 3 core rad would, in effect, increase the cooling capacity by 30%...so, yes, it would help.

Can you post photos of your fan and shroud?

What is your ignition timng?

Could it be exhaust related? I recall that if a heat riser in the exhaust manifold got stuck in the closed (cold) position, it would continue to push hot exhaust over the intake to the opposite side and overheating could result.

does the water pump have a cast impeller? and did you check the clearance between the impeller and divider plate?the closer it is the better.

I'd check the coolant for contamination. With the pressure buildup, it may be an exhaust leak into the water jacket.

Ok, so the car does not have a heat riser on the exhaust manifold.

I have some baffling between the top of the shroud and the radiator support. There is nothing on the sides but a 1/2" gap that could be filled I suppose.

The pressure buildup is from steam not exhaust gasses as this hose blowing event only takes place with the engine off.

The new water pump does not have a cast impeller, and as far as the distance between the plate, it is what it is, not sure how to get it closer.

The car has always run hot,I have just put up with it, but I am on quest to resolve this problem once and for all.

I thought the new plate would solve the problem.

I am leaning toward the 4 row upgrade.

$400

Trying to avoid spending this but it might be money well spent.

Not sure if anyone has addressed this, but the "hot spot" in your manifold is the exhaust runner crossover. It will discolor paint and will be very hot. Should not have any effect on operating temp. Coolant only runs through the front crossover where the t-stat is mounted. Good thing you're in S.F./Bay area, imagine what your temps would be in the summer in the Sacto valley where I'm at!

Thanks for that, this is good info.

I was considering pulling the manifold to inspect, but if there are no cooling passages there that explains the heat.

Cool the engine to 190-200 and that hot spot should not be getting as hot.

May be a little cooler, but that's not really your concern. Focus on the running hot issue at hand.

I guess I meant that if it is "normal" for the engine to be hot there, I will not pull the manifold.

A radiator guy sugessted that that "hot spot" might be an obstructed passageway.

I think the next step is to pull the radiator and have it recored into a 4 row.

While you have your rad out, remove your water pump and make sure your divider plate is no more than 1/16 inch from the impellor blades. Use a hammer to beat into place(while removed from pump, of course). Trial and error...you'll figure it out.

I don't buy into the cast vs. stamped blade comparison. I use a Flow-Kooler pump with 8 shrouded stamped blades. It has worked well for over a year.

Do the baffles and filler panels found stock on 400 and A/C cars mentioned previously do anything to help low speed/idle temps?

Yes, anything that directs air flow through the radiator as opposed to over/under or around will help all speed including standstill idling.

I was experiencing the identical symptoms you were. Changing the radiator to an aluminum radiator made all the difference. I think my old one was clogged or something. I did have it cleaned out by a professional (supposedly), but the old copper one would never make the car run cool. $200 later the car NEVER gets above 190F. Best money I've spent on the car so far. Not saying the radiator is the only potential problem, but it worked for me! I don't even have any of the fillers talked about previously. The only reason I didn't change it out sooner was from lack of research. I was expecting to spend $1200 or so on one of the "Be-Cool" radiators...check eBay...found mine for $200

If the hose is blowing off, either the radiator cap is bad, wrong type, or theres a circulation problem.

I think the hose was blowing off because there was no ridge on the thermostat housing, and when I did the water pump. I sanded and painted the neck making it slick.

I roughend it up and reinstalled it.

I just dropped the radiator off at a classic radiator specialist.

It will be recored into a 4 row high performance.

Supposedly it will "cool a locomotive".

$375 out the door.

Hope this is the issue.

Thanks very much for all the help folks, I will let you know what happens.

My old 3 row was moderatly obstructed.

I installed the recored 4 row-hp radiator,that uses my stock tanks, and now run at 180 on the freeway, and 190-200 after coming off the freeway.

Big improvement.

Thanks for all the advice!

Purrrfect.