Overheating issue...

[danielturbo]

I have a 1984 Reynard and I have some overheating issue on my car.

I ran my car on the track for about 5-7min. and the reserve bottle is full of water and it's bubbling a lot. Each time we bleeded it and added some water and it's still the same.

So far here's what we know:

- The sytem is holding 14psi for over 45 min. and there's no leak.
- I removed the water pump and everything looks fine.
- We blew air trought the radiators and it's circulating properly.
- The sparkplugs looks pretty good.
- The timing is fine but maybe we can play with that a bit.

Any idea

[Brian]

If it's blowing bubbles, that usually means the water system is getting pressurized by the combustion process somehow. if you're lucky - head gasket is blown. If you're not lucky - cracked head or block. If you're really unlucky - crack in a cylinder wall doesn't show up till the engine is hot and you don't think of getting the whole mess crack-checked and you spend a season lo9oking for the problem in your rad system...

Brian

[gord leach]

If you're really unlucky - crack in a cylinder wall doesn't show up till the engine is hot and you don't think of getting the whole mess crack-checked and you spend a season lo9oking for the problem in your rad system...

Brian

do I detect a wee bit of bitterness

Gord

[RussMcB]

Head Gasket or Combustion Leak Test Procedure:

http://www.arrowheadradiator.com/hea..._leak_test.htm

[ghoneycutt]

bublbes with engine running? off? both?

How are the rad's plumbed? example- in through top, out through bottom?

Are you sure there is a complete water circuit through the motor and through the radiators? When I bought my car, someone had criss-crossed the piping. Although the radiators were plumbed, most of the water was leaving the motor, going through the crossover pipes and right back into the motor, taking the path of least resistance and by-passing the radiators.

Are you running a thermostat?

Each radiator has a diverter plate that can come loose and allow the water to enter the radiator through one pipe and take the path of least resistance and leave the other pipe without circulating through the core. If you put a garden hose in one radiator pipe, it should take a while for the water to start coming out of the other pipe because the water has to make it's way through the core. If the water comes out the other pipe immediately, suspect the diverter plate.

Greg

[Gary_T]

To add to Dan's description:

There is no 'white' smoke from the exhaust, it doesn't smell like coolant, the plugs all look fine.

There is no 'bubbling' like exhaust into the coolant looks like.

It 'pops' the 14 psi cap and blows off pressure into the catch tank. While this was happening, a digital pyrometer showed the swirl pot temp to be ~95-100 degrees C.

Swapping rad caps didn't change anything.

Good circulation from the pump.

The rads both get hot, evenly along the length (ie. the end baffle is still in place).

It idled on a 30 C day for ~25 minutes and didn't overheat. Dan can overheat it in minutes on the track.

There is no restriction where the thermostat used to be. I know typically one is installed, but this car has never had one and used to cool fine, and my '84 Reynard doesn't have one and cools fine.

We installed an adjustable cam gear - retarded it approx 3 degrees. Any chance this or ign timing could cause such a temp issue??

Also, carb adjustments lately - the carb isn't 'prepped', it still has the power valve, and seems to go full-on rich at WOT, possible we leaned it too much off WOT to compensate??

Gary

[Gary_T]

Rad plumbing:

Out of block into swirl pot

out of swirl pot - split to go to top of both rads

from both rads - joined to pump inlet

from pump outlet through block

goto 10

I'm not sure about having the flow split from the pot to the rads. My car forces the flow first to one rad, then the other... I don't recall if this is how the rads were setup before the motor was rebuilt or not.

Gary

[Gary_T]

Slow day at the office... and race cars are more fun than what's on my desk...

Dan - let's attach the rad pressure tester, then fire the car... a blown head gasket/cracked head/block will cause pressure spikes with each spark. I'm reasonably sure it's not that.

Get a second temp gauge going to make sure it's at least reasonably correct.

Gary

[danielturbo]

Slow day at the office... and race cars are more fun than what's on my desk...

Dan - let's attach the rad pressure tester, then fire the car... a blown head gasket/cracked head/block will cause pressure spikes with each spark. I'm reasonably sure it's not that.

Get a second temp gauge going to make sure it's at least reasonably correct.

Gary

I bought a electric temp gauge. So we will have to hook it up.

I will do an oil change this week to see if there's water in the oil.

[Gary_T]

Water in the oil will produce 'mayonaise' under the oil tank cap and/or in the valve cover.

[Brian]

retarded ignition timing can cause the engine to run hot, but the car would run badly before that happened. I'm thinking less than 30 degrees total. Too much timing causes the whole burn down the engine thing, which you would see on the plugs.

Brian

[Purple Frog]

Can anyone tell me what the water temp was after that 7 minutes on the track? Never saw that mentioned...

Sounds like a bad cap to me.

(OBTW I run a 20+ lb. cap. )

[Gary_T]

Apparently we never did try the second cap. The existing one did test ok tonight (popped at 16psi on a tester), but we're going to swap my 20psi Stant cap on and try it.

We're not 100% sure that the temp gauge/sender is accurate, so we're going to try a new electric gauge.

We've got a few weeks until our next race, so we'll go over all of this stuff and see what we find.

Keep the ideas coming though!

[ghoneycutt]

Where is the sender located?

[Gary_T]

Currently there is a mechanical temp sender in the bottom of the aluminum swirl pot.

We're going to wire up an electric gauge to the gallery in the block and see how they compare.

Gary

[rickb99]

Jeff noticed a short burst of high (to him, 105 C. ) water temps at Portland 2 weeks ago. Although ambient temps that day were NOT in the range where over temps should have been seen, he backed off slightly for a lap and the temp came back down.

When he came in and mentioned it, I decided to wrap the fill neck with some of the thick silvered heat shield material and allow it to hang down low enough to protect the temp sensor element in the bottom. The entire fill neck and sensor are VERY close to the #1 exhaust header and the headers are uncoated. He didn't see any more high temps during the weekend. BUT, we didn't have any overflow or bubbling issues either.

If you have a similar setup, it could be that the uncoated header really close to that fill neck and sensor could be causing localized boiling inside the fill neck.

Our local formula car prep shop guy came by and we asked him about it. He ( as FROG did) recommended we replace the 16 Lb. cap with a 20. It obviously prevents boiling at higher temps that can lead to a blockage of cooling flow.

As Frog asked, what temps were you seeing?
What was the ambient temp?
Do you have uncoated headers and how close is the filler to it? Ours is like less then 3/4" away.
Were you at full tilt or taking slow laps?

From your initial description with no other info, I'd be thinking head gasket too. However, it may be something simpler.. hope so.

[DaveW]

I didn't see any mention of the possibility that air is going around instead of through the rads. Are they completely sealed so all the air goes through them?

[Gary_T]

Rick/Dave - Thanks - good info there.

Rick, the 84 Reynard has a lot more space in front of the engine than the 89 you run. the swirl pot is likely 6" away from the header. This exact car ran for another friend for a complete season with no overheating - so it shouldn't be a symptom of the way the car is built.

I don't put enough belief in the temp sender to start mentioning #'s, but had they been as high as the guage showed, the engine would be melted.

The ambient temp both weekends was close to 30C (85 F).

Dave, air around the rads as opposed to through is certainly a possibility. We'll look closer at the mounting/pods.

I don't think we'll be able to give an update today/tomorrow - I need a day off from race car stuff after a race weekend. We just got everything unloaded last night.

Gary

[S Lathrop]

I will add one additional thing to think about.

When you pressure test a radiator system you are testing only the full system and the highest pressure the entire system will maintain. More important is the pressure inside the block. You have to restrict the flow of water out of the block in order to maitain the maximum block pressure. Without sufficient block pressure you will have water boil when it comes into contact with hot spots in the head. The higher the block pressure the higher the boiling point of water. Simply removing the thermostat without replacing it with a restrictor will lead to low block pressure and consequently boiling when the engine is at high output.

You need a restrictor that will restrict the water flow to the maximum with the thermostat installed.

Because all of my cars use thermostats, I have no idea what size restrictor you need.

[Gary_T]

I agree that a restrictor is typically suggested for this scenario. However, this car has ran without one for the past 2 years, and this is the first overheating issue we've seen. I don't have one in my '84 and have no overheating issues either.

[Purple Frog]

The reason for my interest in this thread...

My 89 Reynard has been experiencing overheating problems. With a 24 lb cap it didn't boil over, but the guage was pegged. It has one of those dual guages (oil pressure / water temp), and water temp would read about 60 ls on the oil pressure part of the guage. Hot tamales!

I've had the car since spring 2006. It has always been a tad hot ~110 C.
After the March race at Roebling, it seemed to be hovering around 120 C. I expected the usual Reynard rust clogged radiators. So I pulled them out of the car and took them to a local radiator shop. They inspected, and boiled them out and pressure tested them. They reported all was well. For grins I even "rodded" a few of the tubes and felt no resistance. I also tested them to make sure the splitting plate was in place and not leaking.

This car has the trick radiator bleeders that feed up to the swrill pot.

I then pressure tested the whole system, with the engine running, etc. A-OK.

At CMP on Memorial Day it seemed fine in the morning qualifier, but in the race it again pegged the guage. I had my doubts about the guage. So I bought another, but it wouldn't fit in the Ol' English wentworth threaded swirl pot. For grins I tested the two guages side by side with the old boiling water trick and they appeard to read the same. So maybe I had been running the beast at 285 F degrees.

That night i packed foam rubber into any possible air leakage area in the radiator sidepods. On top of that I built aluminum fences to pack another 10 square inches of frontal area into the sidepod openings. Carnut169 marveled at my paddock craftsmanship.

The whole time the engine seemed to be running like a top. No signs of overheating. No weird oil. No bubbling in the swrill pot. No oil in the water. Clean exhaust.

During Sunday's race it pegged the guage again. So as any typical driver racing for first in class would do, I finished the race. On the cool down lap ( it got down to 105 C) I smelled coolant. HUH OH. When I got to impound I saw a pinhole leak in one of the main hoses, where it tore against a clamp as it must have strained at nearly 24psi.

6 weeks later...

Today I finally had time to visit the shop. I added a bit of water, fired up the motor, and got it hot, and did a leak down test.

I then removed the radiators and checked them. I don't see anything wrong. I removed the water pump and inspected it. Looks fine. I removed the inlet pipe. No thermostat. No provision for a thermostat, no little step in the casting. But all of my Reynards have never had one, neither did the Tatuus. I looked at my spare motor (the motor that came in this car) and it has a 1.25" restrictor. That restritor is a thin sheet of metal that is thinner than the compressed gasket.

So I found nothing wrong in the whole cooling system. (unless it needs a restrictor, Steve)

Oh... about the leakdown test... 8-9 hours on this motor...
1 = 95%
2 = 88% squirted in WD40 and it climbed to 94%
3 = 72% Noise in exhaust and some ring bypass.
4 = 95%

The engine didn't seem real happy at idle.

So driving around for 4 or more hours at 280 degrees F probably did cause some problem. But I had a broken shifter a few races back and over-reved the snot out of it, that might have bent #3 exhaust. The heat might have not helped the cylinder walls... or the valve seats... or...

I'll pull the head and get it worked on. But, when it gets back, what do I do to solve the overheating?

Maybe different Reynard sidepods? (car now has Averill ultra sidepods)
Maybe new radiators?
Make a provision for a thermostat/restrictor?

[Gary_T]

PF, that story sounds mighty familiar! The gauge Dan is running is one of the combined oil pressure/water temp ones as well. He too was getting the temp needle well up into the oil pressure area. The engine really, really didn't act like it was that hot though. If it wasn't for the cap venting, I'd have said it was just a faulty gauge and no other issue.

Perhaps tomorrow night we can start on some of these ideas. Leakdown test would be a good one to add.

Gary

[Larry]

If the car worked before, then the problem isn't the side pods. There are a couple different designs for the side pods for the Reynard, and I haven't found any that don't work. Nor have I found any that cure heating problems. Usually it's the rads...

Larry Oliver
International Racing Products

[S Lathrop]

What is the surface area of the Reynard radiator cores?

[DaveW]

1. Maybe different Reynard sidepods? (car now has Averill ultra sidepods)
2. Maybe new radiators?
3. Make a provision for a thermostat/restrictor?

1&2. Generally, the hardest part of cooling is to get heat transfer from the radiators to the air, so 1 and/or 2 may indeed help.
3. If you are not losing coolant or boiling coolant in the head, a restrictor is probably not the solution - remember, getting the heat into the air stream is the hard part, and faster coolant flow (no restrictor) will help that.

[akilcoyne]

What are the oil temps doing?

When checking ignition timing, how high are the revs when you're checking? Some builders use heavier advance springs in the distributor to aid in the cool morning start ups, up here in the "nort". Some distributors wont fully advance until beyond 5000 revs. Suprising what a couple degrees of ignition timing will do to your cooling system efficiency (or lack their of) when its on the ragged edge of detonating.

[Gary_T]

So, we had a chance to play with Dan's car again last night.

As soon as we started it up, the tell-tale lots of small bubbles in the swirl pot showed up. Just at idle, the water was covered with small bubbles, as I rev'd the car, the water swirled, but you could see bigger bubbles.

We attached a rad pressure tester and fired the car. Every blip of the throttle would add 1 or 2 psi, letting it back to idle would drop 1/2 of what was gained. Didn't take long before we were up to the 16 psi mark that would have had his cap blowing off, even though the temp guage was still well below 100C.

Next is to pull the head, check it for straightness, and replace the head gasket. Luckily, on the '84 reynard, this is a dead simple job.

So, that's all the news for now. We'll post back after the hg swap and let everyone know if that was the culprit.

We'll still look at the other variables that folks posted, lots of good ideas in here, thanks.

Gary

[ghoneycutt]

"getting the heat into the air stream is the hard part, and faster coolant flow (no restrictor) will help that."

Dave,

I've read where if the water is moving too quick through the system, the radiators don't have time to cool the fluid- hence the restrictor in place of a thermostst.

Thoughts?

[danielturbo]

"getting the heat into the air stream is the hard part, and faster coolant flow (no restrictor) will help that."

Dave,

I've read where if the water is moving too quick through the system, the radiators don't have time to cool the fluid- hence the restrictor in place of a thermostst.

Thoughts?

I heard that too, someone suggested a bigger water pump pulley to slow down the system, but my pulley is already different than Gary's car. (the other reynard). We will check the head anyway, since we have the time to do it.

[Brian]

My thought on the restrictor in the cooling neck outlet is that it's there to increase the back-pressure within the block to ensure even circulation and to help reduce cavitation at the water pump. speed of flow through the rads has very little impact on the amount of heat transfer, from what various rocket scientists have told me.

The larger water pump pulley is already a decent under-drive to reduce the parasitic power loss from the pump, and can result in overheating at low RPM like during extended pace car laps. You'd want to think about under-driving it more.

Sounds like you have found the root cause, and per my earlier message I sure hope it's just a gasket!

[rickb99]

At this point wouldn't a leak down test help pin point the cylinder that may have the gasket problem?

[Gary_T]

The pump on the 2L pulls water from the rads and pumps it into the block, so a restrictor at the outlet (thermostat housing) will do nothing to stop cavitation of the pump, as far as I can see. It will, however, allow more pressure to be built inside the block, as Steve mentions above. It may be something to try after we get the car back to where it was previously.

I don't really believe that you are able to make coolant flow 'too fast' to pick up the heat from the engine. While each molecule of water may pick up marginally less heat with each pass (due to less time in contact with the hot bits), it makes more passes through the engine due to the higher flow.

Also, pure water (we run redline water wetter as well, not sure how that affects this) boils easier than glycol/etc, so leaving the water in contact with the hot bits longer (lower flow) may actually cause more steam pockets than having a higher flow due to no restriction. I'm not sure how that would work alongside the increased block pressure reducing the tendancy to boil... Not even sure how you would calculate something like that.

Gary

[Gary_T]

Out of curiousity... here's boiling point of water vs pressure.

[Gary_T]

More info:

Q = M x C x Delta T

Where Q = rate of heat transfer
M = mass flow rate
C = Constant (specific heat of water) 4.186 joule/gram °C
Delta T = difference between temp out/temp in.

So, increasing flow rate increases rate of heat transfer.

So, now the question becomes:

How much does a restriction in the thermostat housing reduce flow, and increase block pressure?

I think I should quit now, but this is much more interesting than real work.

Gary

[Brian]

since the pump impeller is basically inside of the block, increasing the pressure in the block is what reduces cavitation. How important is it? I've never had an overheating problem that putting a reducer in the head made a big difference on - on a ford 1600 engine (and I know this is a Pinto). I have had engines where I eventually gave up and ran a thermostat, though. Trying to keep up with how much tape I needed got to be a right pain. there are other engines where there are known cylinder head cooling/ water distribution problems that can be solved by running a restrictor. so I don't think it's an old wives tale, nor do I think it makes all that much difference.

I'm also curious what a leak-down test showed on this puppy? did you/can you do one?

Brian

[Gary_T]

We haven't done a leak down yet, but if we can borrow a leak down gauge from a friend, I'd like to see the results as well.

Sorry Brian, but I'm still a little confused on the reduced cavitation bit... even though the impeller is inside the block, the water it's trying to 'pull' into the block is on the other side of the pump, so shouldn't be seeing the increased pressure, again, as far as I can see (which certainly may not be very far!).

I agree that the restrictor isn't an old-wives tale, hope I didn't give that impression. I too am not sure what sort of a difference it may make though. That's why I've been searching for a water flow rate vs restrictor diameter table... no luck yet.

Gary

[DaveW]

"getting the heat into the air stream is the hard part, and faster coolant flow (no restrictor) will help that."

Dave,

I've read where if the water is moving too quick through the system, the radiators don't have time to cool the fluid- hence the restrictor in place of a thermostst.

Thoughts?

That slower flow gives better heat transfer IS an old wives tale. Faster flow always gives better heat transfer, and increased flow also keeps coolant temperature more uniform throughout the system, helping keep the head cool and improving heat transfer at the cool ends of the radiators and the exit of the engine (the front of the head). The old wives tale about slower flow originates from poorly designed flow paths and hot spots inside the engine that exacerbated localized boiling (cavitation), and slowing the flow (while also increasing coolant pressure in the engine) with a restrictor reduced overheating due to reducing that localized boiling. Thus, it was thought (by hands-on, non-engineering types) that slower flow was good. It was actually the increased pressure in the head caused by the exit restriction that was good, NOT the reduced flow (except for the minor effect of reduced cavitation in the head as a result of the slower flow).

[rickb99]

Interesting discussion about cavitation and internal block boiling related to with or without a thermostat.

Once you have a system that's "restricted enough" to reach proper temps., isn't the with or without thermostat related more to good functioning of the radiators themselves? Too fast a flow and the water to air exchange rate is lower. Thus returning hotter water to the block then you might have with a slower flow through the radiator(s). i.e. if you don't allow a long enough time for the water to air exchange it isn't as efficient as it could be.

What that magic rate is and at what flow rate it becomes less efficient, I have no clue.

[Gary_T]

From the equation above, you CAN'T make the flow 'too fast', you always get better heat transfer with higher flow.

Eventually you would need a pump so big that the engine wouldn't be able to turn it, or the heat generated by the pump would be more than the engine produces, which would skew results somewhat, but I think we can leave those extremes out of this discussion.

Gary

[DaveW]

From the equation above, you CAN'T make the flow 'too fast', you always get better heat transfer with higher flow.

Eventually you would need a pump so big that the engine wouldn't be able to turn it, or the heat generated by the pump would be more than the engine produces, which would skew results somewhat, but I think we can leave those extremes out of this discussion.

Gary

That is, of course, correct. The coolant flow can NEVER be too fast for heat transfer. The "fly in the ointment" is the engine internal cavitation/local-boiling problem, and as you said, the HP loss from the pump.