Replacing camshafts

[collins_dan]

I really believe that it is some sort of flow issue. The radiator and fan are working properly. The timing and mixture are right. The thermostat on the engine and the radiator are indicating the same temp. The engine has been completely overhauled recently including a new water pump. Yet the symptom of rising temp while at idle has been the same throughout. The lower hose is about the only thing that I haven't replaced. What other flow related items can I check? The thermostat on the engine was installed when I got the car 4 years ago as the previous owner was using a reamed out one. I really appreciate the collective brain power, I have been thinking about this one long and hard for quite some time. Dan

[paddy]

To confirm it really is a flow issue, what happens if you short-circuit the fan thermostat and leave it permanently running?

If there is still a problem, and all other external adjustments haven't fixed what seems to be an intrinsic issue with the engine, my money would be on Rohan's suggestion re the water pump impellor clearance; the pump speed is really the only difference between the situation where it is idling (and overheating) and normal running (not overheating).

BTW have you checked the thermostat is opening properly?

Paddy

[collins_dan]

I have an override switch on the fan, so can let it run constantly. All the happens is that it takes a longer time to get up to temp. Once at temp and at a light, it will still continue to run up just the same.

There are a couple of reasons that I do not suspect the water pump. I had this issue before the engine was rebuilt with the old water pump. (The PO told me when I bought the car, that it has always run hot.) I had the engine rebuilt with a new water pump, and the problem of running hot while in motion has stopped, but the running hot in traffic continues. The engine rebuild and pump installation was done by someone who has been working on lotuses for probably 30 years now. If he was doing it wrong, everyone in this area would be having the same issue.

The only other thing that I haven't mentioned yet is that the car also has an oil cooler, which I would think would be further helping to reduce the engine temp.

Maybe the engine thermostat is not fully opening. Its been a constant throughout my ownership.

Appreciate the thinking. Dan

[paddy]

If replacing the pump did partially resolve the problem, then maybe that's a reasonably good clue to there being a flow restriction elsewhere.

Removing the stat completely would be a good test.

Paddy

[collins_dan]

That's what I'm thinking. First, I'll replace the lower hose, as last summer when I cut it down from the original twist to just a 90 degree turn, I saw a marked improvement and thought I actually had the problem licked. If that doesn't do it, then I'll pull the thermostat completely and see what happens. Thanks for the help. Dan

[johnsimister]

Maybe the thermostat opens at too high a temperature. My car ran hotter - sometimes a lot hotter - than I liked when I bought it, and it turned out to have an 88-degree (Celsius, obviously) stat. I replaced it with an 82-degree one and now the temp needle sits half way round the scale plus or minus a bit, apart from a surge of heat just before the stat opens for the first time on a run. The thermostat's rated temperature should be marked on it somewhere.

John

[neilsjuke]

you must not remove the stat as the water may bypass parts of the head it will take the easy route
Neil

[rgh0]

Removing the thermostat totally is not adviable but the reason is a little different. The flow does not "bypass parts of the head taking the easy route". Any increase or decrease in the water flow rate affects all parts of the head in proportion - the high flow parts get more or less and the low flow parts get more or less in the same proportion. You dont want low flow parts getting so little that you get localosed vaporisation and overheating but this is not the problem we are talking about here.

The potential problem in removing the thermo stat is:

1. You loose pressure difference across the heater and reduce its flow and effectiveness
2. Without the thermostat restriction you get higher total flow in the cooling circuit, at that high flow rate the pump may start to cavitate and loose suction and then the flow drops, the pumps starts working again flow increases, cavitation again etc. This process results in an unstable circulation which can result in an average lower flow and engine overheating, plus pump damage. However I dont think this is a real problem in practice in an elan cooling system that I have ever observed.


regards
Rohan

[CBUEB1771]

The flow does not "bypass parts of the head taking the easy route". Any increase or decrease in the water flow rate affects all parts of the head in proportion - the high flow parts get more or less and the low flow parts get more or less in the same proportion. n an elan cooling system that I have ever observed.

I respectfully disagree, having spent the first part of may career balancing flows in various parts of electric power generation plants. The restriction imposed by the thermostat is large compared to the restriction through any path through the block or head. This balances flow though the various passages in the block and head by making the differences in restrictions among them negligible in context of the overall system restriction. If the thermostat is removed the distribution of coolant flow in the engine will change significantly. Removing the thermostat reduces the overall pumping loss through the system and actually reduces the likelihood that cavitation will occur at the inlet to the water pump. However locally higher velocities at points within the block and head increase the likelihood that cavitation will occur at those locations within the block and head.

[rgh0]

I think if you draw it up and think about it you will see that what I said was correct.

For any flow path through the head or block
Pressure Drop = k x Volume squared

k is constant for any particular flow path.

The pressure drop available from the pump discharge to the thermostat is the same for each flow path as they all start at the pump and finish at the thermo stat. As the themostat opens the pressure drop available increases and flow increases in all paths in proportion with the formula above. Remove the thermostat totally and the available pressure drop is the maximum and the flow the maximum in all flow paths.

Centrifugal Pumps required NPSH ( net positive suction head) increases with flow rate. The absolute pressure at the pump suction also drops with increasing flow rate due to increased pressure drop through the radiator. The combination of these 2 affects can lead to the pressure to drop low enough at the pump suction to casue cavitation at high flows with the thermostat removed. However as i said before I dont beleive this point is reached in an Elan system with the thermostat removed.

regards
Rohan

[collins_dan]

The water pump that I had installed during the engine rebuild was one of Dave Bean's cartridge units. I've heard some disparage their quality in very general terms. Can anyone who has had a bad experience with one of these units please clarify what the problem has been and provide any insight if it is a possible explanation of what I am experiencing with the engine heating up in traffic. Thanks. Dan

[Carlos A]

This is a great topic. I hope somebody comes up with an answer.

This the list of common causes (http://www.salemboysauto.com/original-faqs/faq-19.htm):

"1. Lack of coolant. This is created by a leak and the symptoms are typically the same each time it overheats. You fill up the radiator, everything is OK for awhile (20 miles maybe) then it overheats. It overheats because the leak creates a shortage of water or coolant. The repair is to simply pressure test the cooling system and find and fix the leak.

2. Lack of circulation. This is caused by a closed thermostat, a plugged radiator or a bad waterpump belt or a bad waterpump.

3. The engine is consuming the coolant. This is created by a bad head gasket or a broken engine block and has some very specific symptoms. ''



Keep us posted

Carlos A

[rgh0]

I dont think an exhaust system leak into cooling water - as the water will generally go the other way and you would bee suffering from loss of coolant which I dont think is the case.

My bet is still either the fan not cooling the section of radiator where the water flows at idle or to low water circulation at idle due to blockage or pump problem. Testing temperatures around the system should be able to distinguish between the 2 options.

cheers
Rohan

[Carlos A]

I dont think an exhaust system leak into cooling water - as the water will generally go the other way and you would bee suffering from loss of coolant which I dont think is the case. My bet is still either the fan not cooling the section of radiator where the water flows at idle or to low water circulation at idle due to blockage or pump problem. Testing temperatures around the system should be able to distinguish between the 2 options. cheers Rohan

Rohan: Yes. You may be right. The water pump or some sort of blockage seem to be obvious causes of this.

As for my hypotesis, there is a product to test leaks of exhaust gases into the coolant (which sometimes happens). It is sort of a 'blue die in that you put on your coolant overflow tank and when the bubbles pass through the liquid it will turn yellow it if there is any exhaust gas (hydrocarbons) in the cooling system.


Best,

Carlos

[collins_dan]

I was away last weekend, so haven't had a chance to check everything out (timing, mixture, fan, lower hose, thermostat), but am worrying about the pump. Two questions: 1) Could the belt be slipping at low speeds, but not at faster speeds? 2) Since its a removable water pump, is it possible to check and adjust if there is too much clearance between the impellor face and the housing without pulling the engine? What would I need to do to check this? Thanks. Dan