running hot - help

lovethycobra · #1 (**permalink**) 07-13-2010, 04:07 AM

I am new to this board so please bare with me as I get used to it!! I have a MK IV with lightweight conversion (ak 1171) - problem - runs extremely hot and chokes off fuel when at standstill in warm weather - car has no bonnet scoop and fan working fine (biggest fan available) - and is otherwise completely original...any ideas? I would prefer to keep as original as possible but if necessary I would install air scoop on bonnet if I was sure that would solve the problem - appreciate any suggestions you may have!!!!!!!!!

Clois Harlan · #2 (**permalink**) 07-13-2010, 05:08 AM

A scoop will not solve your problem. I am wondering if you are not running a little to lean and possibly have to much advance in your distributor. Then of course these little cars have a problem with air in the system. Once you have your car started have you tried to bleed excess air from your intake where your water temp probe is installed in the manifold?

Heat could also be caused by a bad head gasket or some other sealing issue. What is the bore of your engine (how much over did you go)?

Clois

Tommy · #3 (**permalink**) 07-13-2010, 05:12 AM

A little more information would be helpful in diagnosing your problem. What temperatures are you seeing in the engine coolant when the engine dies? Does the engine have fuel injection or a carburetor? Do you have an electric or mechanical fuel pump? Has this always happened or is it a recent phenomenon? What is your distributor timing and do you have a vacuum advance?

lovethycobra · #4 (**permalink**) 07-13-2010, 05:21 AM

engine is original (302) but I replaced the EFI with edlebrook carb - bore not changed. Problem did not occur until new carbs installed. Temp on motorway runs just right (about 70c) as does the rest of the car but at a standstill runs well into 115 / 120c. Not sure what the dist. timing is but yes has a vacuum advance. all gaskets seem fine (and would expect that to cause problems constantly rather than just at a standstill.

lovethycobra · #5 (**permalink**) 07-13-2010, 06:15 AM

sorry, just to round up the rest of the questions / suggestions:
timing is set to 12 deg btdc
Mech. fuel pump (working fine)
Also, the fan does kick in at the right time which to me would suggest that it would not be an issue with air in the system (although I do not consider myself an expert at this by any means!!)
I have also just checked to make sure the evaporation plate between the carb is there and it is....appreciate all your help!!

Tommy · #6 (**permalink**) 07-13-2010, 07:07 AM

A temperature of 115/120 C at a standstill seems the fundamental problem to me. Since it runs at a much cooler 70 C on the road, I suggest you check two things first. One is the air flow over the radiator. For example, if you are using a puller fan (aft of the radiator), be sure there is a shroud that directs the air through the radiator before it goes through the fan. The other thing is the timing at idle. I suggest you put a timing light on the engine at idle, then remove the vacuum line to the distributor and cover the hose (to prevent a leak). If your vacuum can was working correctly, you should see the timing advance (e.g., from 5 degrees BTDC to 12 degrees BTDC). If you don't see the advance, that may also be contributing to your overheating at idle.

jhv48 · #7 (**permalink**) 07-13-2010, 07:44 AM

Runs fine at speed, overheats at idle.

Two things:

1. Probably not, but feel radiator hoses at idle and see if they are hot. If not hot, replace thermostat.

3. Most likely, since car runs fine at speed, when air is being forced through the radiator, either you need a shroud to make your fan more effective, your fan is turning the wrong way, or your radiator and/or fan is too small.

My choice is the shroud, then the fan.

Jerry Clayton · #8 (**permalink**) 07-13-2010, 08:43 AM

Underdrive pulleys????not enough water flow at idle, not enough voltage to run the fan, and not enough fan

lovethycobra · #9 (**permalink**) 07-13-2010, 10:02 AM

ok - tomorrow is a day of testing...thanks for all of your input and I will let you know if / what I find - any more suggestions always welcome!!

JBCOBRA · #10 (**permalink**) 07-13-2010, 10:34 AM

If the distributor is too retarded, then they get extra hot.

lovethycobra · #11 (**permalink**) 07-13-2010, 11:36 AM

it has been suggested that insulating the manifold would help reduce the heat substantially in the engine bay - may try that once I have exhausted some of the other options

jhv48 · #12 (**permalink**) 07-13-2010, 11:47 AM

Quote:

Originally Posted by lovethycobra

it has been suggested that insulating the manifold would help reduce the heat substantially in the engine bay - may try that once I have exhausted some of the other options

Do a search on that subject before you actually attempt any insulation. There are a lot of conflicting opinions on insulating the exhaust.

lovethycobra · #13 (**permalink**) 07-13-2010, 11:51 AM

thanks all - will let you know how it goes tomorrow...

lovethycobra · #14 (**permalink**) 07-14-2010, 11:38 AM

results are in (sort of...) - so running the engine with hood fully open or fully closed has no impact on the problem. feeling around the radiator I did find some patches that didn't burn my hand as much as others (ouch). So it looks like it there are 2 problems - 1. engine heating problem "probably" fixable with new aluminium rad (which is being done next week). 2. The "choking and stalling" is either unrelated to the heat problem which suggests it could simply need some tweeking of the carbs or back to the drawing board!! Thank you all for your very valuable input - it has been a very pleasureable first experience on the board and I look forward to continuing in many other discussions!!!

badrich · #15 (**permalink**) 07-14-2010, 01:55 PM

This has been mentioned a couple of times, and since you are installing a new radiator, make sure you have a close fitting shroud around your fan. Made all the difference in the world for me after I installed my Shelby motor. Even aluminium motors can get hot. Make the shroud out of brushed aluminum with nice welds and it will look pretty too. My engine runs on the road at a consistent 180ºF, but to keep it there when I get into the hills or around town, I flip my trusty Lucas

switch. Rich

Tommy · #16 (**permalink**) 07-14-2010, 02:02 PM

I fully agree with the shroud recommendation.

I'm not sure I fully understand why you're changing out the radiator. Is there something more you haven't mentioned, or do you plan to change parts until something works?

lovethycobra · #17 (**permalink**) 07-14-2010, 02:11 PM

Changing the radiator mainly because there are some cool spots on it (can put my hand against it without burning it in some spots!!) - I guess i could just flush it and see how well it goes but it is 25 yrs old and looking a bit shabby / rusty...I will def. ensure I have a very well fitting shroud and I like the idea of doing it in aluminium as well...will give results next week!! thanks again to all

MFE III · #18 (**permalink**) 07-14-2010, 04:08 PM

Quote:

Problem did not occur until new carbs installed.

This leads me to think it's your timing or running too lean.
Matt