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Chrysler 426 Exhaust over heating

T

tjksail

New member
Hello,
I have a Chrysler 426 Wedge, which was Model M-426B in a 1967 Century Coronado. The engine has been running great, but I have started having a problem where the starboard exhaust manifold, exhaust elbow and exhaust pipe run way too hot at idle. However, at speed the manifold, elbow and exhaust all cool down to appropriate temp. The port side is fine. Stays at appropriate temp no matter the load or speed.

I was looking at the cooling diagram for this engine which I have attached. It is quite complex. Has 2 impellers in one pump. I don't suspect this is a pump issue as the engine itself runs at the correct temp and the port side is fine as well. All impellers and gaskets were replaced last season and have maybe 20 hrs use.

My suspicion is there may be some obstruction between 9 and 8 on the starboard side? I'm just puzzled because the problem resolves at higher RPMs and is worse at idle.

Does this make sense to anyone? Screen Shot 2022-03-06 at 5.17.51 PM.jpg
 
i'd be concerned about the rest of the water pump as well...Cams wear out and reduce the product the pump delivers and it sounds like your raw water flow is marginal at idle. it would also be good to ensure ALL connections on the suction side of the pump are tight...air doesn't cool worth a damn...

based on your theory and the diagram, you should be able to reverse the T connections at the outlet from 9.
 
makomark said:
i'd be concerned about the rest of the water pump as well...Cams wear out and reduce the product the pump delivers and it sounds like your raw water flow is marginal at idle. it would also be good to ensure ALL connections on the suction side of the pump are tight...air doesn't cool worth a damn...

based on your theory and the diagram, you should be able to reverse the T connections at the outlet from 9.
Click to expand...


Thanks for the reply. Wouldn’t the block cooling circuit also overheat at idle if it was a pump volume issue? I’ve never been hot at the heads or intake. What would be the best way to check this?

Good idea on reversing the connections from the oil cooler output to the manifolds. That will help isolate
 
Ayuh,..... Ya might also wanta check the exhaust manifold/ riser too,.....

Ya have to get water in, but ya also have to let the water out, 'n crudded up manifolds/ risers certainly could be blocked,....
 
tjksail said:
...
Wouldn’t the block cooling circuit also overheat at idle if it was a pump volume issue? I’ve never been hot at the heads or intake.
...
Click to expand...
your plumbing diagram shows two separate circuits, where the block and heads are in one loop and the exhaust manifolds are in the other. So, a problem in one half may not have any impact on the other half.

As far as checking it, I'd suggest check the flow at the discharge from each exhaust manifold, at idle and say 1500 RPM. Best way is to measure it. for that, use a bucket and a stopwatch...catch what comes out of the hose for 15 seconds and then measure it...repeat two more times...and then calculate the average flow rate...do same for the other side.

As Bondo noted, any restrictions will impede the flow and reduce the cooling...it could be a casting filled with crud or a hose delaminating in the inside.
 
makomark said:
your plumbing diagram shows two separate circuits, where the block and heads are in one loop and the exhaust manifolds are in the other. So, a problem in one half may not have any impact on the other half.

As far as checking it, I'd suggest check the flow at the discharge from each exhaust manifold, at idle and say 1500 RPM. Best way is to measure it. for that, use a bucket and a stopwatch...catch what comes out of the hose for 15 seconds and then measure it...repeat two more times...and then calculate the average flow rate...do same for the other side.

As Bondo noted, any restrictions will impede the flow and reduce the cooling...it could be a casting filled with crud or a hose delaminating in the inside.
Click to expand...


still working on this issue. Manifolds are cool to the touch at idle, elbows get just a bit to hot to touch at idle. They cool at higher RPM. I have not measured the temps yet, but what is a reasonable wet exhaust and elbow temp at idle? Normal for it to be higher at idle?
 
warmer at idle could be a small restriction or the pump being marginal at low speed...

based on the plumbing diagram, the exhaust manifold will likely be 'cold'....I'd say it may see up to a 25-30 degree rise from the inlet water's temp as an upper bound. The elbows get a blend of the water from the manifold and the 'warm water' from the tstat outlet....likely to be at the t-stat's rated temp....so, it's temp will vary with the component flows, but shouldn't exceed the t-stat housing temp by more than 5 degrees or so...

An IR temp gun is a huge asset for resolving cooling system issues...
 
May not be the same issue since yours is raw water cooled - I had a 318 that ran hot at idle/low speeds but cooled right down at higher RPM. I ran thru the system and the only thing that seemed amiss was the raw water pump, even after I replaced the impeller. I stripped it down and saw that the bronze housing was pretty worn so I replaced the whole pump. That seemed to clear things up for me.
 
makomark said:
warmer at idle could be a small restriction or the pump being marginal at low speed...

based on the plumbing diagram, the exhaust manifold will likely be 'cold'....I'd say it may see up to a 25-30 degree rise from the inlet water's temp as an upper bound. The elbows get a blend of the water from the manifold and the 'warm water' from the tstat outlet....likely to be at the t-stat's rated temp....so, it's temp will vary with the component flows, but shouldn't exceed the t-stat housing temp by more than 5 degrees or so...

An IR temp gun is a huge asset for resolving cooling system issues...
Click to expand...


Update: I had a hose that had a bit of a kink on the inner wall going from the exhaust manifold to the elbow on the starboard side. Additionally, there was in fact bits of old vane at the intake of the gear oil cooler on the starboard side. Flushing this out did help. Now I run about 115 at the manifolds at idle and 130-145 at the elbows at idle. Both cool down at higher RPMS.

I do have a question about the bypass that goes from the thermostat housing back to the intake circuit. Per the service manual, this is to keep the pump primed and always with a flow of water and I presume to help the engine warm. However, when I warmed up the engine, then too the line off of the intake of the gear oil cooler, it was quite hot, probably 130-140 (140 thermostat). The pump has 2 impellers and circuits (one for the manifolds and one for the block). I expected the water coming from the pump to be pretty much the temp of the intake water but I guess a lot of it is being recirculated? Seems like this would be really counterproductive especially at idle.

Any thoughts?
 
That 'bypass' isn't explicit in the diagram and likely alters the temps you've seen. I didn't find the explanation you did in the little bit of Chrysler literature I have.

After re-reading it, I'd say the bypass helps to warm up the engine and then keep it close to the t-stat's operating point while at low RPM...my guess is that the water temp at the gear oil cooler will drop at higher RPMs as the bulk of the 'warm' water should exit thru the exhaust elbows...
 
The diagram is a little misleading. In reality, the bypass come right off the t stat housing (6) and Ts back in with the inlet line. There is no line that goes from the thermostat housing to the intake. That is just cooled by the block circuit. There is no dedicated intake manifold hose.

I guess with all of that being said, I’ll just accept that this is probably ok and just supposed to run a little warmer at the exhausts at idle?
 
i believe that is reasonable...you may want try posting that specific question in the Chrysler section...there are a few that really understand the nuances of the chrysler approaches...
 
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