Ok I’ve got a question that I need some help with. On the XR7G we have had some on and off cooling issues. We have put on a new water pump, flushed the radiator/engine, replaced the thermostat with a new 180* unit. Sometimes within the first ten or so miles after start up the temp gauge will fluctuate towards hot then eventually level off a little past half way between cold and hot. We hooked up a remote mechanical gauge and had a reading that stayed near 180 but would rise slightly over 200*.
On a cold start up with the hood up the choke was engaged with high idle the bottom radiator hose was almost sucked flat. Shut the engine off and opened the radiator cap and the hose expanded. This isn’t normal is it? At least I wouldn’t think so. What could be the cause? Should the hose have a spring inside of it to keep this from happening? Could this be the cause of the higher temp readings in the first couple of miles of driving after start up? Any thoughts would be helpful.
Steven
Replace the radiator cap.
X2 on the radiator cap. My J-Code did the exact same thing this winter. New cap solved the problem.
Not going against the voices of experience here, but curious. What about the radiator cap is causing this? Also, what about the spring in the lower hose, shouldn’t there be one? I think my concours repro lower (D0AE) has one but I am not sure.
I’ll take a stab at this, though I may be incorrect…
I would think the cap would need to be able to vent, much like the gas cap, so when the coolant flows, there is no “suction”, causing said collapsed hose??
Easy enough to replace the radiator cap, so hopefully that will be the fix.
Bob I was wondering the same thing about the cap and spring in the hose.
This “stab” makes a lot of sense.
Thanks for the replies I’ll try the cap and keep you all updated.
Steven
If I remember correctly, it was Royce who said that the spring in the lower hose was only there because of the way the coolant was vacuum-pulled into the car when it was built at the factory, and it is totally irrelevant to the operation of the car.
If the bottom hose is collapsing that sounds to me like there is blockage in the radiator that is preventing the coolant from being properly drawn through it. But I know almost nothing about cars still, so…
Scott the radiator was flushed and does not appear to have any blockages.
I agree that the spring is there for the vacuum created in the cooling system.
Not sure I agree with this part. If the spring is totally irrelevant to the operation of the car wouldnt the engineers have just left it out if it wasn’t needed?
Still have not changed the cap yet, it’s been a busy week for my brother at work.
Steven
The closed thermostat in a cold engine is causing the suction. Maybe the hose is old and soft? I’ve never seen one sucked flat unless the hose was just about to fail. You don’t need the spring in the hose in any case.
Once the engine warms up the cooling system is always pressurized. The original caps don’t allow any suction to build up in the system, so I agree you probably have the wrong radiator cap or a bad one.
Royce thanks for the follow up. I agree about the hose might be going bad. It could be breaking down from the inside by softening. Radiator cap and hose replacement are easy enough fixes.
Steven
Steven I thought it was Royce who had explained once before that the reason the engineers put that spring in the bottom hose was because of the way the coolant was pulled into the system at the factory, during the building of the car, and that the spring was only put there to serve that purpose for that one moment in time during the manufacture of the car. If it wasn’t him, it was someone else who said it here that I trust enough to take it as gospel.
The cooling issues seem to be fixed now. The upper and lower radiator hoses were replaced along with the radiator cap. The lower radiator hose is staying in it’s correct dimensions and not collapsing. So these fixes were easy and were all done at the same time. My brother and I are not sure if one item was the problem or it was a combination of the cap and hose failing. Either way it’s a good peace of mind knowing that you’ve got a cool running engine under the hood. Thanks for the suggestions and input on the replies to my post.
Steven
Kevin Marti Answered this question pretty completely in his FAQ section:
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I need a spring for my radiator hose. Where can I find one?
The thought that a spring is needed in a radiator hose is a common misconception, that springs (pun intended) from two events.
The first is that many (although not all) lower radiator hoses on the production assembly line had springs in them. The reason for this was the method by which the assembly lines filled the cooling systems. To save time, a special vacuum/fill fitting was placed over the radiator fill connection (the place where the radiator cap would eventually be placed. A vacuum machine was turned on to evacuate most of the air out of the cooling system. Once completed, the fill portion was turned on to introduce the coolant into the system. This process avoided entrained air preventing the system from being completed filled. The purpose of the hose spring was to prevent collapse during the vacuum portion of the fill cycle.
The second part of the story that has led to the “I need a spring” myth is that some people have observed their lower hose collapsing when they rev the engine. This is the result of a clogged radiator or a cooling system that has not been brought up to standard operating temperature. If an engine is revved up while still cool, there is only atmospheric pressure in the system. It is possible for the lower hose to collapse slightly due to the water pump drawing water out of the lower hose faster than the gravity-fed water from the radiator replaces it. Once the engine has been warmed up, the coolant system operates under pressure and this condition doesn’t exist in a properly maintained cooling system. However, if the radiator tubes have restrictions, as the engine is revved, the water pump pulls coolant from the lower hose faster than water can trickle past the clogged tubes. This can result in a reduction in internal pressure that would cause the hose to collapse.
Note that the events that lead to the thought that “I need a spring” are based on either an insufficiently warmed up engine or a clogged radiator. The spring does not take care of these events. It merely masks a symptom. If, after your vehicle has reached normal operating temperature but you experience a collapsing hose, have your radiator tested.
As an additional thought, have you ever wondered where your original spring went? Did you ever find bits and pieces of it scattered throughout the cooling system? Being made of ordinary steel, they corrode with time, small pieces gradually breaking off and either scoring the water pump impeller, tearing the water pump seal, or clogging the radiator. They aren’t necessary for the functioning of a properly maintained cooling system.
That part is interesting! Well, all of it was interesting, but this part really got my attention.
Bill your post answers a lot of the questions that Dennis and I had with the hose issue. A very interesting read. It’s just as Scott stated in his earlier post. He had it spot on. The information this site brings together is great. Thanks again everyone.
Steven